diff --git a/GNUmakefile b/GNUmakefile
index fb300a566b..321eaca77b 100644
--- a/GNUmakefile
+++ b/GNUmakefile
@@ -387,9 +387,7 @@ TEST_PACKAGES_FAST = \
 
 # archive/zip requires os.ReadAt, which is not yet supported on windows
 # bytes requires mmap
-# compress/flate appears to hang on wasi; on all targets Go 1.27's new
-#   compress/flate.indexTokens returns a ~262KB struct by value which crashes
-#   LLVM's X86 instruction selector during LTO codegen
+# compress/flate appears to hang on wasi
 # crypto/aes needs reflect.Type.Method(), not yet implemented
 # crypto/des fails on wasi, needs panic()/recover()
 # crypto/hmac fails on wasi, it exits with a "slice out of range" panic
@@ -411,6 +409,7 @@ TEST_PACKAGES_FAST = \
 # Additional standard library packages that pass tests on individual platforms
 TEST_PACKAGES_LINUX := \
 	archive/zip \
+	compress/flate \
 	context \
 	crypto/aes \
 	crypto/des \
@@ -438,6 +437,7 @@ TEST_PACKAGES_DARWIN := $(TEST_PACKAGES_LINUX)
 
 # os/user requires t.Skip() support
 TEST_PACKAGES_WINDOWS := \
+	compress/flate \
 	crypto/des \
 	crypto/hmac \
 	image \
diff --git a/compiler/calls.go b/compiler/calls.go
index 08952c4db6..257973320e 100644
--- a/compiler/calls.go
+++ b/compiler/calls.go
@@ -35,6 +35,9 @@ const (
 
 	// Whether this is a readonly parameter (for example, a string pointer).
 	paramIsReadonly
+
+	// Whether this parameter is passed through backing storage.
+	paramIsIndirect
 )
 
 // createRuntimeCallCommon creates a runtime call. Use createRuntimeCall or
@@ -102,6 +105,18 @@ func (b *builder) createInvoke(fnType llvm.Type, fn llvm.Value, args []llvm.Valu
 // Expand an argument type to a list that can be used in a function call
 // parameter list.
 func (c *compilerContext) expandFormalParamType(t llvm.Type, name string, goType types.Type) []paramInfo {
+	if c.isIndirectAggregate(t) {
+		return []paramInfo{{
+			llvmType: c.dataPtrType,
+			name:     name,
+			elemSize: c.targetData.TypeAllocSize(t),
+			flags:    paramIsGoParam | paramIsReadonly | paramIsIndirect,
+		}}
+	}
+	return c.expandDirectFormalParamType(t, name, goType)
+}
+
+func (c *compilerContext) expandDirectFormalParamType(t llvm.Type, name string, goType types.Type) []paramInfo {
 	switch t.TypeKind() {
 	case llvm.StructTypeKind:
 		fieldInfos := c.flattenAggregateType(t, name, goType)
@@ -115,6 +130,38 @@ func (c *compilerContext) expandFormalParamType(t llvm.Type, name string, goType
 	return []paramInfo{c.getParamInfo(t, name, goType)}
 }
 
+func (c *compilerContext) storedParamType(t llvm.Type, exported bool) llvm.Type {
+	if c.isIndirectParam(t, exported) {
+		return c.dataPtrType
+	}
+	return t
+}
+
+func (c *compilerContext) isIndirectParam(t llvm.Type, exported bool) bool {
+	return !exported && c.isIndirectAggregate(t)
+}
+
+func (b *builder) appendStoredValueTypes(valueTypes []llvm.Type, values []ssa.Value, exported bool) []llvm.Type {
+	for _, value := range values {
+		valueTypes = append(valueTypes, b.storedParamType(b.getLLVMType(value.Type()), exported))
+	}
+	return valueTypes
+}
+
+func (b *builder) appendStoredParamTypes(valueTypes []llvm.Type, params []*types.Var, exported bool) []llvm.Type {
+	for _, param := range params {
+		valueTypes = append(valueTypes, b.storedParamType(b.getLLVMType(param.Type()), exported))
+	}
+	return valueTypes
+}
+
+func (b *builder) prependIndirectResult(sig *types.Signature, exported bool, params []llvm.Value, name string) []llvm.Value {
+	if resultType, indirect := b.hasIndirectResult(sig); !exported && indirect {
+		return append([]llvm.Value{b.createIndirectStorage(resultType, name)}, params...)
+	}
+	return params
+}
+
 // expandFormalParamOffsets returns a list of offsets from the start of an
 // object of type t after it would have been split up by expandFormalParam. This
 // is useful for debug information, where it is necessary to know the offset
diff --git a/compiler/channel.go b/compiler/channel.go
index 82139de8ba..a562e97e3a 100644
--- a/compiler/channel.go
+++ b/compiler/channel.go
@@ -30,17 +30,15 @@ func (b *builder) createMakeChan(expr *ssa.MakeChan) llvm.Value {
 // actual channel send operation during goroutine lowering.
 func (b *builder) createChanSend(instr *ssa.Send) {
 	ch := b.getValue(instr.Chan, getPos(instr))
-	chanValue := b.getValue(instr.X, getPos(instr))
 
 	// store value-to-send
 	valueType := b.getLLVMType(instr.X.Type())
 	isZeroSize := b.targetData.TypeAllocSize(valueType) == 0
-	var valueAlloca, valueAllocaSize llvm.Value
+	var storage valueStorage
 	if isZeroSize {
-		valueAlloca = llvm.ConstNull(b.dataPtrType)
+		storage.ptr = llvm.ConstNull(b.dataPtrType)
 	} else {
-		valueAlloca, valueAllocaSize = b.createTemporaryAlloca(valueType, "chan.value")
-		b.CreateStore(chanValue, valueAlloca)
+		storage = b.getValueStorage(instr.X, "chan.value")
 	}
 
 	// Allocate buffer for the channel operation.
@@ -48,15 +46,13 @@ func (b *builder) createChanSend(instr *ssa.Send) {
 	channelOpAlloca, channelOpAllocaSize := b.createTemporaryAlloca(channelOp, "chan.op")
 
 	// Do the send.
-	b.createRuntimeInvoke("chanSend", []llvm.Value{ch, valueAlloca, channelOpAlloca}, "")
+	b.createRuntimeInvoke("chanSend", []llvm.Value{ch, storage.ptr, channelOpAlloca}, "")
 
 	// End the lifetime of the allocas.
 	// This also works around a bug in CoroSplit, at least in LLVM 8:
 	// https://bugs.llvm.org/show_bug.cgi?id=41742
 	b.emitLifetimeEnd(channelOpAlloca, channelOpAllocaSize)
-	if !isZeroSize {
-		b.emitLifetimeEnd(valueAlloca, valueAllocaSize)
-	}
+	b.endValueStorage(storage)
 }
 
 // createChanRecv emits a pseudo chan receive operation. It is lowered to the
@@ -66,37 +62,17 @@ func (b *builder) createChanRecv(unop *ssa.UnOp) llvm.Value {
 	ch := b.getValue(unop.X, getPos(unop))
 
 	// Allocate memory to receive into.
-	isZeroSize := b.targetData.TypeAllocSize(valueType) == 0
-	var valueAlloca, valueAllocaSize llvm.Value
-	if isZeroSize {
-		valueAlloca = llvm.ConstNull(b.dataPtrType)
-	} else {
-		valueAlloca, valueAllocaSize = b.createTemporaryAlloca(valueType, "chan.value")
-	}
+	result := b.createRuntimeValueResult(valueType, unop.CommaOk, true, "chan")
 
 	// Allocate buffer for the channel operation.
 	channelOp := b.getLLVMRuntimeType("channelOp")
 	channelOpAlloca, channelOpAllocaSize := b.createTemporaryAlloca(channelOp, "chan.op")
 
 	// Do the receive.
-	commaOk := b.createRuntimeCall("chanRecv", []llvm.Value{ch, valueAlloca, channelOpAlloca}, "")
-	var received llvm.Value
-	if isZeroSize {
-		received = llvm.ConstNull(valueType)
-	} else {
-		received = b.CreateLoad(valueType, valueAlloca, "chan.received")
-		b.emitLifetimeEnd(valueAlloca, valueAllocaSize)
-	}
+	commaOk := b.createRuntimeCall("chanRecv", []llvm.Value{ch, result.valuePtr, channelOpAlloca}, "")
+	received := result.finish(b, commaOk, "chan.received")
 	b.emitLifetimeEnd(channelOpAlloca, channelOpAllocaSize)
-
-	if unop.CommaOk {
-		tuple := llvm.Undef(b.ctx.StructType([]llvm.Type{valueType, b.ctx.Int1Type()}, false))
-		tuple = b.CreateInsertValue(tuple, received, 0, "")
-		tuple = b.CreateInsertValue(tuple, commaOk, 1, "")
-		return tuple
-	} else {
-		return received
-	}
+	return received
 }
 
 // createChanClose closes the given channel.
@@ -170,9 +146,7 @@ func (b *builder) createSelect(expr *ssa.Select) llvm.Value {
 		case types.SendOnly:
 			// Store this value in an alloca and put a pointer to this alloca
 			// in the send state.
-			sendValue := b.getValue(state.Send, state.Pos)
-			alloca := llvmutil.CreateEntryBlockAlloca(b.Builder, sendValue.Type(), "select.send.value")
-			b.CreateStore(sendValue, alloca)
+			alloca := b.getSelectSendStorage(state.Send)
 			selectState = b.CreateInsertValue(selectState, alloca, 1, "")
 		default:
 			panic("unreachable")
@@ -280,7 +254,17 @@ func (b *builder) getChanSelectResult(expr *ssa.Extract) llvm.Value {
 		// receive can proceed at a time) so we'll get that alloca, bitcast
 		// it to the correct type, and dereference it.
 		recvbuf := b.selectRecvBuf[expr.Tuple.(*ssa.Select)]
-		typ := b.getLLVMType(expr.Type())
-		return b.CreateLoad(typ, recvbuf, "")
+		return b.loadFromStorage(recvbuf, expr.Type(), "select.received")
+	}
+}
+
+func (b *builder) getSelectSendStorage(value ssa.Value) llvm.Value {
+	typ := b.getLLVMType(value.Type())
+	if b.isIndirectAggregate(typ) {
+		return b.getValuePointer(value)
 	}
+	llvmValue := b.getValue(value, getPos(value))
+	ptr := llvmutil.CreateEntryBlockAlloca(b.Builder, typ, "select.send.value")
+	b.CreateStore(llvmValue, ptr)
+	return ptr
 }
diff --git a/compiler/compiler.go b/compiler/compiler.go
index 8cbc1a919a..46ad506a54 100644
--- a/compiler/compiler.go
+++ b/compiler/compiler.go
@@ -155,6 +155,8 @@ type builder struct {
 	llvmFn            llvm.Value
 	info              functionInfo
 	locals            map[ssa.Value]llvm.Value // local variables
+	indirectValues    map[ssa.Value]llvm.Value
+	indirectReturn    llvm.Value
 	blockInfo         []blockInfo
 	currentBlock      *ssa.BasicBlock
 	currentBlockInfo  *blockInfo
@@ -193,6 +195,7 @@ func newBuilder(c *compilerContext, irbuilder llvm.Builder, f *ssa.Function) *bu
 		llvmFn:          fn,
 		info:            c.getFunctionInfo(f),
 		locals:          make(map[ssa.Value]llvm.Value),
+		indirectValues:  make(map[ssa.Value]llvm.Value),
 		dilocals:        make(map[*types.Var]llvm.Metadata),
 	}
 }
@@ -1282,10 +1285,28 @@ func (b *builder) createFunctionStart(intrinsic bool) {
 
 	// Load function parameters
 	llvmParamIndex := 0
+	if _, indirectResult := b.hasIndirectResult(b.fn.Signature); indirectResult && !b.info.exported {
+		b.indirectReturn = b.llvmFn.Param(llvmParamIndex)
+		b.indirectReturn.SetName("return")
+		llvmParamIndex++
+	}
 	for _, param := range b.fn.Params {
 		llvmType := b.getLLVMType(param.Type())
+		if b.isIndirectParam(llvmType, b.info.exported) {
+			llvmParam := b.llvmFn.Param(llvmParamIndex)
+			llvmParam.SetName(param.Name())
+			b.indirectValues[param] = llvmParam
+			llvmParamIndex++
+			continue
+		}
+		var paramInfos []paramInfo
+		if b.info.exported {
+			paramInfos = b.expandDirectFormalParamType(llvmType, param.Name(), param.Type())
+		} else {
+			paramInfos = b.expandFormalParamType(llvmType, param.Name(), param.Type())
+		}
 		fields := make([]llvm.Value, 0, 1)
-		for _, info := range b.expandFormalParamType(llvmType, param.Name(), param.Type()) {
+		for _, info := range paramInfos {
 			param := b.llvmFn.Param(llvmParamIndex)
 			param.SetName(info.name)
 			fields = append(fields, param)
@@ -1423,7 +1444,7 @@ func (b *builder) createFunction() {
 	for _, phi := range b.phis {
 		block := phi.ssa.Block()
 		for i, edge := range phi.ssa.Edges {
-			llvmVal := b.getValue(edge, getPos(phi.ssa))
+			llvmVal := b.getCallArgument(edge, false)
 			llvmBlock := b.blockInfo[block.Preds[i].Index].exit
 			phi.llvm.AddIncoming([]llvm.Value{llvmVal}, []llvm.BasicBlock{llvmBlock})
 		}
@@ -1432,6 +1453,9 @@ func (b *builder) createFunction() {
 	if b.NeedsStackObjects {
 		// Track phi nodes.
 		for _, phi := range b.phis {
+			if b.isOversizedAggregate(phi.ssa.Type()) {
+				continue
+			}
 			insertPoint := llvm.NextInstruction(phi.llvm)
 			for !insertPoint.IsAPHINode().IsNil() {
 				insertPoint = llvm.NextInstruction(insertPoint)
@@ -1523,10 +1547,7 @@ func (b *builder) createInstruction(instr ssa.Instruction) {
 			b.diagnostics = append(b.diagnostics, err)
 			b.locals[instr] = llvm.Undef(b.getLLVMType(instr.Type()))
 		} else {
-			b.locals[instr] = value
-			if len(*instr.Referrers()) != 0 && b.NeedsStackObjects {
-				b.trackExpr(instr, value)
-			}
+			b.setValue(instr, value)
 		}
 	case *ssa.DebugRef:
 		// ignore
@@ -1546,10 +1567,8 @@ func (b *builder) createInstruction(instr ssa.Instruction) {
 		b.CreateBr(blockJump)
 	case *ssa.MapUpdate:
 		m := b.getValue(instr.Map, getPos(instr))
-		key := b.getValue(instr.Key, getPos(instr))
-		value := b.getValue(instr.Value, getPos(instr))
 		mapType := instr.Map.Type().Underlying().(*types.Map)
-		b.createMapUpdate(mapType.Key(), m, key, value, instr.Pos())
+		b.createMapUpdate(mapType.Key(), m, instr.Key, instr.Value, instr.Pos())
 	case *ssa.Panic:
 		value := b.getValue(instr.X, getPos(instr))
 		b.createRuntimeInvoke("_panic", []llvm.Value{value}, "")
@@ -1558,19 +1577,7 @@ func (b *builder) createInstruction(instr ssa.Instruction) {
 		if b.hasDeferFrame() {
 			b.createRuntimeCall("destroyDeferFrame", []llvm.Value{b.deferFrame}, "")
 		}
-		if len(instr.Results) == 0 {
-			b.CreateRetVoid()
-		} else if len(instr.Results) == 1 {
-			b.CreateRet(b.getValue(instr.Results[0], getPos(instr)))
-		} else {
-			// Multiple return values. Put them all in a struct.
-			retVal := llvm.ConstNull(b.llvmFn.GlobalValueType().ReturnType())
-			for i, result := range instr.Results {
-				val := b.getValue(result, getPos(instr))
-				retVal = b.CreateInsertValue(retVal, val, i, "")
-			}
-			b.CreateRet(retVal)
-		}
+		b.createReturn(instr.Results, getPos(instr))
 	case *ssa.RunDefers:
 		// Note where we're going to put the rundefers block
 		run := b.insertBasicBlock("rundefers.block")
@@ -1584,18 +1591,246 @@ func (b *builder) createInstruction(instr ssa.Instruction) {
 		b.createChanSend(instr)
 	case *ssa.Store:
 		llvmAddr := b.getValue(instr.Addr, getPos(instr))
-		llvmVal := b.getValue(instr.Val, getPos(instr))
 		b.createNilCheck(instr.Addr, llvmAddr, "store")
-		if b.targetData.TypeAllocSize(llvmVal.Type()) == 0 {
+		llvmType := b.getLLVMType(instr.Val.Type())
+		if b.targetData.TypeAllocSize(llvmType) == 0 {
 			// nothing to store
 			return
 		}
-		b.CreateStore(llvmVal, llvmAddr)
+		b.storeValue(llvmAddr, instr.Val)
 	default:
 		b.addError(instr.Pos(), "unknown instruction: "+instr.String())
 	}
 }
 
+func (b *builder) setValue(value ssa.Value, llvmValue llvm.Value) {
+	if b.isAggregateValue(value.Type()) && !llvmValue.IsNil() && llvmValue.Type().TypeKind() == llvm.PointerTypeKind {
+		b.indirectValues[value] = llvmValue
+		return
+	}
+	b.locals[value] = llvmValue
+	if len(*value.Referrers()) != 0 && b.NeedsStackObjects {
+		b.trackExpr(value, llvmValue)
+	}
+}
+
+func (b *builder) createReturn(results []ssa.Value, pos token.Pos) {
+	if len(results) == 0 {
+		b.CreateRetVoid()
+	} else if !b.indirectReturn.IsNil() {
+		if len(results) == 1 {
+			b.storeValue(b.indirectReturn, results[0])
+		} else {
+			returnType := b.getLLVMResultType(b.fn.Signature)
+			for i, result := range results {
+				fieldPtr := b.CreateStructGEP(returnType, b.indirectReturn, i, "")
+				b.storeValue(fieldPtr, result)
+			}
+		}
+		b.CreateRetVoid()
+	} else if len(results) == 1 {
+		b.CreateRet(b.getValue(results[0], pos))
+	} else {
+		result := llvm.ConstNull(b.llvmFn.GlobalValueType().ReturnType())
+		for i, value := range results {
+			result = b.CreateInsertValue(result, b.getValue(value, pos), i, "")
+		}
+		b.CreateRet(result)
+	}
+}
+
+func (b *builder) isOversizedAggregate(typ types.Type) bool {
+	if !b.isAggregateValue(typ) {
+		return false
+	}
+	return b.isIndirectAggregate(b.getLLVMType(typ))
+}
+
+func (b *builder) isAggregateValue(typ types.Type) bool {
+	if tuple, ok := typ.(*types.Tuple); ok {
+		for i := 0; i < tuple.Len(); i++ {
+			if !isLLVMValueType(tuple.At(i).Type()) {
+				return false
+			}
+		}
+	} else {
+		switch typ.Underlying().(type) {
+		case *types.Array, *types.Struct:
+		default:
+			return false
+		}
+		if !isLLVMValueType(typ) {
+			return false
+		}
+	}
+	return true
+}
+
+func (b *builder) getValuePointer(value ssa.Value) llvm.Value {
+	if ptr, ok := b.indirectValues[value]; ok {
+		return ptr
+	}
+	llvmType := b.getLLVMType(value.Type())
+	ptr := b.createIndirectStorage(llvmType, value.Name())
+	b.storeValue(ptr, value)
+	return ptr
+}
+
+func (b *builder) getCallArgument(value ssa.Value, exported bool) llvm.Value {
+	paramType := b.getLLVMType(value.Type())
+	if b.isIndirectParam(paramType, exported) {
+		return b.getValuePointer(value)
+	}
+	return b.getValue(value, getPos(value))
+}
+
+func (b *builder) createIndirectStorage(typ llvm.Type, name string) llvm.Value {
+	// Use runtime.alloc here so storage that escapes remains valid. The
+	// allocation optimizer moves bounded non-escaping storage to the stack.
+	size := llvm.ConstInt(b.uintptrType, b.targetData.TypeAllocSize(typ), false)
+	layout := b.createObjectLayout(typ, b.fn.Pos())
+	ptr := b.createAlloc(size, layout, b.targetData.ABITypeAlignment(typ), name)
+	if b.NeedsStackObjects {
+		b.trackPointer(ptr)
+	}
+	return ptr
+}
+
+func (b *builder) copyIndirectAggregate(dst, src llvm.Value, typ llvm.Type) {
+	size := llvm.ConstInt(b.uintptrType, b.targetData.TypeAllocSize(typ), false)
+	b.createMemCopy("memcpy", dst, src, size)
+}
+
+func (b *builder) storeValue(dst llvm.Value, value ssa.Value) {
+	typ := b.getLLVMType(value.Type())
+	if src, ok := b.indirectValues[value]; ok {
+		b.copyIndirectAggregate(dst, src, typ)
+	} else {
+		b.CreateStore(b.getValue(value, getPos(value)), dst)
+	}
+}
+
+func (b *builder) copyToIndirectStorage(src llvm.Value, typ llvm.Type, name string) llvm.Value {
+	dst := b.createIndirectStorage(typ, name)
+	b.copyIndirectAggregate(dst, src, typ)
+	return dst
+}
+
+func (b *builder) loadFromStorage(ptr llvm.Value, typ types.Type, name string) llvm.Value {
+	llvmType := b.getLLVMType(typ)
+	if b.isIndirectAggregate(llvmType) {
+		return b.copyToIndirectStorage(ptr, llvmType, name)
+	}
+	return b.CreateLoad(llvmType, ptr, name)
+}
+
+func (b *builder) getValueField(value ssa.Value, index int, resultType types.Type, name string) (llvm.Value, bool) {
+	if !b.isAggregateValue(value.Type()) {
+		return llvm.Value{}, false
+	}
+	valueType := b.getLLVMType(value.Type())
+	if _, indirect := b.indirectValues[value]; !indirect && !b.isIndirectAggregate(valueType) {
+		return llvm.Value{}, false
+	}
+	fieldPtr := b.CreateStructGEP(valueType, b.getValuePointer(value), index, "")
+	return b.loadFromStorage(fieldPtr, resultType, name), true
+}
+
+func (b *builder) zeroIndirectStorage(ptr llvm.Value, typ llvm.Type) {
+	memset := b.getMemsetFunc()
+	b.createCall(memset.GlobalValueType(), memset, []llvm.Value{
+		ptr,
+		llvm.ConstInt(b.ctx.Int8Type(), 0, false),
+		llvm.ConstInt(b.uintptrType, b.targetData.TypeAllocSize(typ), false),
+		llvm.ConstInt(b.ctx.Int1Type(), 0, false),
+	}, "")
+}
+
+type valueStorage struct {
+	ptr, size llvm.Value
+	temporary bool
+}
+
+func (b *builder) getValueStorage(value ssa.Value, name string) valueStorage {
+	typ := b.getLLVMType(value.Type())
+	if b.isIndirectAggregate(typ) {
+		return valueStorage{ptr: b.getValuePointer(value)}
+	}
+	ptr, size := b.createTemporaryAlloca(typ, name)
+	b.storeValue(ptr, value)
+	return valueStorage{ptr: ptr, size: size, temporary: true}
+}
+
+func (b *builder) endValueStorage(storage valueStorage) {
+	if storage.temporary {
+		b.emitLifetimeEnd(storage.ptr, storage.size)
+	}
+}
+
+type runtimeValueResult struct {
+	valueType  llvm.Type
+	resultType llvm.Type
+	result     llvm.Value
+	valuePtr   llvm.Value
+	valueSize  llvm.Value
+	temporary  bool
+	zero       bool
+	commaOk    bool
+}
+
+func (b *builder) createRuntimeValueResult(valueType llvm.Type, commaOk, zeroAsNull bool, name string) runtimeValueResult {
+	result := runtimeValueResult{
+		valueType:  valueType,
+		resultType: valueType,
+		valueSize:  llvm.ConstInt(b.uintptrType, b.targetData.TypeAllocSize(valueType), false),
+		commaOk:    commaOk,
+	}
+	if commaOk {
+		result.resultType = b.ctx.StructType([]llvm.Type{valueType, b.ctx.Int1Type()}, false)
+	}
+	if b.isIndirectAggregate(result.resultType) {
+		result.result = b.createIndirectStorage(result.resultType, name+".result")
+		result.valuePtr = result.result
+		if commaOk {
+			result.valuePtr = b.CreateStructGEP(result.resultType, result.result, 0, "")
+		}
+		return result
+	}
+	if zeroAsNull && b.targetData.TypeAllocSize(valueType) == 0 {
+		result.valuePtr = llvm.ConstNull(b.dataPtrType)
+		result.zero = true
+		return result
+	}
+	result.valuePtr, result.valueSize = b.createTemporaryAlloca(valueType, name+".value")
+	result.temporary = true
+	return result
+}
+
+func (r runtimeValueResult) finish(b *builder, commaOk llvm.Value, name string) llvm.Value {
+	if !r.result.IsNil() {
+		if r.commaOk {
+			b.CreateStore(commaOk, b.CreateStructGEP(r.resultType, r.result, 1, ""))
+		}
+		return r.result
+	}
+
+	var value llvm.Value
+	if r.zero {
+		value = llvm.ConstNull(r.valueType)
+	} else {
+		value = b.CreateLoad(r.valueType, r.valuePtr, name)
+	}
+	if r.temporary {
+		b.emitLifetimeEnd(r.valuePtr, r.valueSize)
+	}
+	if !r.commaOk {
+		return value
+	}
+	result := llvm.Undef(r.resultType)
+	result = b.CreateInsertValue(result, value, 0, "")
+	return b.CreateInsertValue(result, commaOk, 1, "")
+}
+
 // createBuiltin lowers a builtin Go function (append, close, delete, etc.) to
 // LLVM IR. It uses runtime calls for some builtins.
 func (b *builder) createBuiltin(argTypes []types.Type, argValues []llvm.Value, callName string, pos token.Pos) (llvm.Value, error) {
@@ -2030,14 +2265,10 @@ func (b *builder) createFunctionCall(instr *ssa.CallCommon) (llvm.Value, error)
 		}
 	}
 
-	var params []llvm.Value
-	for _, param := range instr.Args {
-		params = append(params, b.getValue(param, getPos(instr)))
-	}
-
 	// Try to call the function directly for trivially static calls.
 	var callee, context llvm.Value
 	var calleeType llvm.Type
+	var invokeTypecode, invokeReceiver llvm.Value
 	exported := false
 	if fn := instr.StaticCallee(); fn != nil {
 		calleeType, callee = b.getFunction(fn)
@@ -2067,19 +2298,18 @@ func (b *builder) createFunctionCall(instr *ssa.CallCommon) (llvm.Value, error)
 		exported = info.exported
 	} else if call, ok := instr.Value.(*ssa.Builtin); ok {
 		// Builtin function (append, close, delete, etc.).)
+		var params []llvm.Value
 		var argTypes []types.Type
 		for _, arg := range instr.Args {
 			argTypes = append(argTypes, arg.Type())
+			params = append(params, b.getValue(arg, getPos(instr)))
 		}
 		return b.createBuiltin(argTypes, params, call.Name(), instr.Pos())
 	} else if instr.IsInvoke() {
 		// Interface method call (aka invoke call).
 		itf := b.getValue(instr.Value, getPos(instr)) // interface value (runtime._interface)
-		typecode := b.CreateExtractValue(itf, 0, "invoke.func.typecode")
-		value := b.CreateExtractValue(itf, 1, "invoke.func.value") // receiver
-		// Prefix the params with receiver value and suffix with typecode.
-		params = append([]llvm.Value{value}, params...)
-		params = append(params, typecode)
+		invokeTypecode = b.CreateExtractValue(itf, 0, "invoke.func.typecode")
+		invokeReceiver = b.CreateExtractValue(itf, 1, "invoke.func.value")
 		callee = b.getInvokeFunction(instr)
 		calleeType = callee.GlobalValueType()
 		context = llvm.Undef(b.dataPtrType)
@@ -2093,7 +2323,23 @@ func (b *builder) createFunctionCall(instr *ssa.CallCommon) (llvm.Value, error)
 		b.createNilCheck(instr.Value, callee, "fpcall")
 	}
 
+	var params []llvm.Value
+	for _, param := range instr.Args {
+		params = append(params, b.getCallArgument(param, exported))
+	}
+	if instr.IsInvoke() {
+		params = append([]llvm.Value{invokeReceiver}, params...)
+		params = append(params, invokeTypecode)
+	}
+
 	if !exported {
+		if resultType, indirectResult := b.hasIndirectResult(instr.Signature()); indirectResult {
+			result := b.createIndirectStorage(resultType, "call.result")
+			params = append([]llvm.Value{result}, params...)
+			params = append(params, context)
+			b.createInvoke(calleeType, callee, params, "")
+			return result, nil
+		}
 		// This function takes a context parameter.
 		// Add it to the end of the parameter list.
 		params = append(params, context)
@@ -2132,6 +2378,9 @@ func (b *builder) getValue(expr ssa.Value, pos token.Pos) llvm.Value {
 		return value
 	default:
 		// other (local) SSA value
+		if value, ok := b.indirectValues[expr]; ok {
+			return b.CreateLoad(b.getLLVMType(expr.Type()), value, "")
+		}
 		if value, ok := b.locals[expr]; ok {
 			return value
 		} else {
@@ -2214,8 +2463,15 @@ func (b *builder) createExpr(expr ssa.Value) (llvm.Value, error) {
 		// This instruction changes the type, but the underlying value remains
 		// the same. This is often a no-op, but sometimes we have to change the
 		// LLVM type as well.
-		x := b.getValue(expr.X, getPos(expr))
 		llvmType := b.getLLVMType(expr.Type())
+		if b.isIndirectAggregate(llvmType) {
+			sourceType := b.getLLVMType(expr.X.Type())
+			if !b.isIndirectAggregate(sourceType) || b.targetData.TypeAllocSize(sourceType) != b.targetData.TypeAllocSize(llvmType) {
+				return llvm.Value{}, errors.New("todo: indirect aggregate ChangeType with different layout")
+			}
+			return b.getValuePointer(expr.X), nil
+		}
+		x := b.getValue(expr.X, getPos(expr))
 		if x.Type() == llvmType {
 			// Different Go type but same LLVM type (for example, named int).
 			// This is the common case.
@@ -2245,9 +2501,15 @@ func (b *builder) createExpr(expr ssa.Value) (llvm.Value, error) {
 		if _, ok := expr.Tuple.(*ssa.Select); ok {
 			return b.getChanSelectResult(expr), nil
 		}
+		if value, ok := b.getValueField(expr.Tuple, expr.Index, expr.Type(), expr.Name()); ok {
+			return value, nil
+		}
 		value := b.getValue(expr.Tuple, getPos(expr))
 		return b.CreateExtractValue(value, expr.Index, ""), nil
 	case *ssa.Field:
+		if value, ok := b.getValueField(expr.X, expr.Field, expr.Type(), expr.Name()); ok {
+			return value, nil
+		}
 		value := b.getValue(expr.X, getPos(expr))
 		result := b.CreateExtractValue(value, expr.Field, "")
 		return result, nil
@@ -2270,11 +2532,11 @@ func (b *builder) createExpr(expr ssa.Value) (llvm.Value, error) {
 	case *ssa.Global:
 		panic("global is not an expression")
 	case *ssa.Index:
-		collection := b.getValue(expr.X, getPos(expr))
 		index := b.getValue(expr.Index, getPos(expr))
 
 		switch xType := expr.X.Type().Underlying().(type) {
 		case *types.Basic: // extract byte from string
+			collection := b.getValue(expr.X, getPos(expr))
 			// Value type must be a string, which is a basic type.
 			if xType.Info()&types.IsString == 0 {
 				panic("lookup on non-string?")
@@ -2308,13 +2570,12 @@ func (b *builder) createExpr(expr ssa.Value) (llvm.Value, error) {
 
 			// Can't load directly from array (as index is non-constant), so
 			// have to do it using an alloca+gep+load.
-			arrayType := collection.Type()
-			alloca, allocaSize := b.createTemporaryAlloca(arrayType, "index.alloca")
-			b.CreateStore(collection, alloca)
+			arrayType := b.getLLVMType(expr.X.Type())
+			storage := b.getValueStorage(expr.X, "index.alloca")
 			zero := llvm.ConstInt(b.ctx.Int32Type(), 0, false)
-			ptr := b.CreateInBoundsGEP(arrayType, alloca, []llvm.Value{zero, index}, "index.gep")
-			result := b.CreateLoad(arrayType.ElementType(), ptr, "index.load")
-			b.emitLifetimeEnd(alloca, allocaSize)
+			ptr := b.CreateInBoundsGEP(arrayType, storage.ptr, []llvm.Value{zero, index}, "index.gep")
+			result := b.loadFromStorage(ptr, expr.Type(), "index.load")
+			b.endValueStorage(storage)
 			return result, nil
 		default:
 			panic("unknown *ssa.Index type")
@@ -2373,17 +2634,21 @@ func (b *builder) createExpr(expr ssa.Value) (llvm.Value, error) {
 		}
 	case *ssa.Lookup: // map lookup
 		value := b.getValue(expr.X, getPos(expr))
-		index := b.getValue(expr.Index, getPos(expr))
 		valueType := expr.Type()
 		if expr.CommaOk {
 			valueType = valueType.(*types.Tuple).At(0).Type()
 		}
-		return b.createMapLookup(expr.X.Type().Underlying().(*types.Map).Key(), valueType, value, index, expr.CommaOk, expr.Pos())
+		return b.createMapLookup(expr.X.Type().Underlying().(*types.Map).Key(), valueType, value, expr.Index, expr.CommaOk, expr.Pos())
 	case *ssa.MakeChan:
 		return b.createMakeChan(expr), nil
 	case *ssa.MakeClosure:
 		return b.parseMakeClosure(expr)
 	case *ssa.MakeInterface:
+		if b.isOversizedAggregate(expr.X.Type()) {
+			typ := b.getLLVMType(expr.X.Type())
+			ptr := b.copyToIndirectStorage(b.getValuePointer(expr.X), typ, "interface.value")
+			return b.createMakeInterfaceFromPointer(ptr, expr.X.Type()), nil
+		}
 		val := b.getValue(expr.X, getPos(expr))
 		return b.createMakeInterface(val, expr.X.Type(), expr.Pos()), nil
 	case *ssa.MakeMap:
@@ -2450,7 +2715,8 @@ func (b *builder) createExpr(expr ssa.Value) (llvm.Value, error) {
 			return b.createMapIteratorNext(rangeVal, llvmRangeVal, it), nil
 		}
 	case *ssa.Phi:
-		phi := b.CreatePHI(b.getLLVMType(expr.Type()), "")
+		phiType := b.storedParamType(b.getLLVMType(expr.Type()), false)
+		phi := b.CreatePHI(phiType, "")
 		b.phis = append(b.phis, phiNode{expr, phi})
 		return phi, nil
 	case *ssa.Range:
@@ -3453,8 +3719,7 @@ func (b *builder) createUnOp(unop *ssa.UnOp) (llvm.Value, error) {
 			return fn, nil
 		} else {
 			b.createNilCheck(unop.X, x, "deref")
-			load := b.CreateLoad(valueType, x, "")
-			return load, nil
+			return b.loadFromStorage(x, unop.Type(), ""), nil
 		}
 	case token.XOR: // ^x, toggle all bits in integer
 		return b.CreateXor(x, llvm.ConstInt(x.Type(), ^uint64(0), false), ""), nil
diff --git a/compiler/compiler_test.go b/compiler/compiler_test.go
index e5d781849b..ad486989af 100644
--- a/compiler/compiler_test.go
+++ b/compiler/compiler_test.go
@@ -52,6 +52,7 @@ func TestCompiler(t *testing.T) {
 		{"gc.go", "", ""},
 		{"zeromap.go", "", ""},
 		{"generics.go", "", ""},
+		{"large.go", "", ""},
 	}
 	if goMinor >= 20 {
 		tests = append(tests, testCase{"go1.20.go", "", ""})
@@ -130,6 +131,46 @@ func TestCompiler(t *testing.T) {
 	}
 }
 
+func TestOptimizedLargeAggregateABI(t *testing.T) {
+	options := &compileopts.Options{Target: "wasm"}
+	mod, errs := testCompilePackage(t, options, "large-optimized.go")
+	if len(errs) != 0 {
+		for _, err := range errs {
+			t.Error(err)
+		}
+		return
+	}
+	defer mod.Dispose()
+
+	passOptions := llvm.NewPassBuilderOptions()
+	defer passOptions.Dispose()
+	if err := mod.RunPasses("default<O2>", llvm.TargetMachine{}, passOptions); err != nil {
+		t.Fatal(err)
+	}
+
+	resultFn := mod.NamedFunction("main.makeLargeOptimizedValue")
+	if resultFn.IsNil() {
+		t.Fatal("missing function main.makeLargeOptimizedValue")
+	}
+	if resultType := resultFn.GlobalValueType().ReturnType(); resultType.TypeKind() != llvm.VoidTypeKind {
+		t.Errorf("large aggregate result was promoted to %s", resultType)
+	}
+
+	for _, name := range []string{
+		"main.makeLargeOptimizedValue",
+		"main.readLargeOptimizedValue",
+		"main.readMixedLargeOptimizedValue",
+	} {
+		fn := mod.NamedFunction(name)
+		if fn.IsNil() {
+			t.Fatalf("missing function %s", name)
+		}
+		if paramType := fn.GlobalValueType().ParamTypes()[0]; paramType.TypeKind() != llvm.PointerTypeKind {
+			t.Errorf("%s aggregate parameter was promoted to %s", name, paramType)
+		}
+	}
+}
+
 // fuzzyEqualIR returns true if the two LLVM IR strings passed in are roughly
 // equal. That means, only relevant lines are compared (excluding comments
 // etc.).
@@ -257,6 +298,49 @@ func TestCompilerErrors(t *testing.T) {
 	}
 }
 
+func TestAggregateValueCount(t *testing.T) {
+	t.Parallel()
+
+	ctx := llvm.NewContext()
+	defer ctx.Dispose()
+
+	byteType := ctx.Int8Type()
+	tests := []struct {
+		name     string
+		typ      llvm.Type
+		count    uint64
+		exceeded bool
+	}{
+		{"empty", llvm.ArrayType(byteType, 0), 0, false},
+		{"limit", llvm.ArrayType(byteType, 1024), 1024, false},
+		{"over limit", llvm.ArrayType(byteType, 1025), 0, true},
+		{"combined limit", ctx.StructType([]llvm.Type{
+			llvm.ArrayType(byteType, 512),
+			llvm.ArrayType(byteType, 512),
+		}, false), 1024, false},
+		{"combined over limit", ctx.StructType([]llvm.Type{
+			llvm.ArrayType(byteType, 1000),
+			llvm.ArrayType(byteType, 1000),
+		}, false), 0, true},
+		{"comma-ok over limit", ctx.StructType([]llvm.Type{
+			llvm.ArrayType(byteType, 1024),
+			ctx.Int1Type(),
+		}, false), 0, true},
+	}
+
+	for _, test := range tests {
+		t.Run(test.name, func(t *testing.T) {
+			count, exceeded := aggregateValueCount(test.typ, 0)
+			if exceeded != test.exceeded {
+				t.Errorf("expected exceeded=%t, got %t", test.exceeded, exceeded)
+			}
+			if !exceeded && count != test.count {
+				t.Errorf("expected count=%d, got %d", test.count, count)
+			}
+		})
+	}
+}
+
 // Build a package given a number of compiler options and a file.
 func testCompilePackage(t *testing.T, options *compileopts.Options, file string) (llvm.Module, []error) {
 	target, err := compileopts.LoadTarget(options)
diff --git a/compiler/defer.go b/compiler/defer.go
index 4fd9715b52..ddde9eee10 100644
--- a/compiler/defer.go
+++ b/compiler/defer.go
@@ -359,6 +359,44 @@ type tarjanNode struct {
 	cyclic bool
 }
 
+type llvmValueList struct {
+	values []llvm.Value
+	types  []llvm.Type
+}
+
+func newLLVMValueList(values ...llvm.Value) llvmValueList {
+	var list llvmValueList
+	list.append(values...)
+	return list
+}
+
+func (l *llvmValueList) append(values ...llvm.Value) {
+	for _, value := range values {
+		l.values = append(l.values, value)
+		l.types = append(l.types, value.Type())
+	}
+}
+
+func (l *llvmValueList) appendSSAValues(values []ssa.Value, lower func(ssa.Value) llvm.Value) {
+	for _, value := range values {
+		l.append(lower(value))
+	}
+}
+
+func (b *builder) loadDeferredCallParams(structType llvm.Type, ptr llvm.Value) []llvm.Value {
+	fieldTypes := structType.StructElementTypes()
+	values := make([]llvm.Value, 0, len(fieldTypes)-2)
+	zero := llvm.ConstInt(b.ctx.Int32Type(), 0, false)
+	for i := 2; i < len(fieldTypes); i++ {
+		fieldPtr := b.CreateInBoundsGEP(structType, ptr, []llvm.Value{
+			zero,
+			llvm.ConstInt(b.ctx.Int32Type(), uint64(i), false),
+		}, "gep")
+		values = append(values, b.CreateLoad(fieldTypes[i], fieldPtr, "param"))
+	}
+	return values
+}
+
 // createDefer emits a single defer instruction, to be run when this function
 // returns.
 func (b *builder) createDefer(instr *ssa.Defer) {
@@ -366,8 +404,10 @@ func (b *builder) createDefer(instr *ssa.Defer) {
 	// make a linked list.
 	next := b.CreateLoad(b.dataPtrType, b.deferPtr, "defer.next")
 
-	var values []llvm.Value
-	valueTypes := []llvm.Type{b.uintptrType, next.Type()}
+	var values llvmValueList
+	lowerArgument := func(value ssa.Value) llvm.Value {
+		return b.getCallArgument(value, false)
+	}
 	if instr.Call.IsInvoke() {
 		// Method call on an interface.
 
@@ -384,13 +424,8 @@ func (b *builder) createDefer(instr *ssa.Defer) {
 		itf := b.getValue(instr.Call.Value, getPos(instr)) // interface
 		typecode := b.CreateExtractValue(itf, 0, "invoke.func.typecode")
 		receiverValue := b.CreateExtractValue(itf, 1, "invoke.func.receiver")
-		values = []llvm.Value{callback, next, typecode, receiverValue}
-		valueTypes = append(valueTypes, b.dataPtrType, b.dataPtrType)
-		for _, arg := range instr.Call.Args {
-			val := b.getValue(arg, getPos(instr))
-			values = append(values, val)
-			valueTypes = append(valueTypes, val.Type())
-		}
+		values = newLLVMValueList(callback, next, typecode, receiverValue)
+		values.appendSSAValues(instr.Call.Args, lowerArgument)
 
 	} else if callee, ok := instr.Call.Value.(*ssa.Function); ok {
 		// Regular function call.
@@ -402,12 +437,11 @@ func (b *builder) createDefer(instr *ssa.Defer) {
 
 		// Collect all values to be put in the struct (starting with
 		// runtime._defer fields).
-		values = []llvm.Value{callback, next}
-		for _, param := range instr.Call.Args {
-			llvmParam := b.getValue(param, getPos(instr))
-			values = append(values, llvmParam)
-			valueTypes = append(valueTypes, llvmParam.Type())
-		}
+		values = newLLVMValueList(callback, next)
+		exported := b.getFunctionInfo(callee).exported
+		values.appendSSAValues(instr.Call.Args, func(value ssa.Value) llvm.Value {
+			return b.getCallArgument(value, exported)
+		})
 
 	} else if makeClosure, ok := instr.Call.Value.(*ssa.MakeClosure); ok {
 		// Immediately applied function literal with free variables.
@@ -430,14 +464,9 @@ func (b *builder) createDefer(instr *ssa.Defer) {
 		// Collect all values to be put in the struct (starting with
 		// runtime._defer fields, followed by all parameters including the
 		// context pointer).
-		values = []llvm.Value{callback, next}
-		for _, param := range instr.Call.Args {
-			llvmParam := b.getValue(param, getPos(instr))
-			values = append(values, llvmParam)
-			valueTypes = append(valueTypes, llvmParam.Type())
-		}
-		values = append(values, context)
-		valueTypes = append(valueTypes, context.Type())
+		values = newLLVMValueList(callback, next)
+		values.appendSSAValues(instr.Call.Args, lowerArgument)
+		values.append(context)
 
 	} else if builtin, ok := instr.Call.Value.(*ssa.Builtin); ok {
 		var argTypes []types.Type
@@ -460,11 +489,8 @@ func (b *builder) createDefer(instr *ssa.Defer) {
 
 		// Collect all values to be put in the struct (starting with
 		// runtime._defer fields).
-		values = []llvm.Value{callback, next}
-		for _, param := range argValues {
-			values = append(values, param)
-			valueTypes = append(valueTypes, param.Type())
-		}
+		values = newLLVMValueList(callback, next)
+		values.append(argValues...)
 
 	} else {
 		funcValue := b.getValue(instr.Call.Value, getPos(instr))
@@ -479,20 +505,15 @@ func (b *builder) createDefer(instr *ssa.Defer) {
 		// Collect all values to be put in the struct (starting with
 		// runtime._defer fields, followed by all parameters including the
 		// context pointer).
-		values = []llvm.Value{callback, next, funcValue}
-		valueTypes = append(valueTypes, funcValue.Type())
-		for _, param := range instr.Call.Args {
-			llvmParam := b.getValue(param, getPos(instr))
-			values = append(values, llvmParam)
-			valueTypes = append(valueTypes, llvmParam.Type())
-		}
+		values = newLLVMValueList(callback, next, funcValue)
+		values.appendSSAValues(instr.Call.Args, lowerArgument)
 	}
 
 	// Make a struct out of the collected values to put in the deferred call
 	// struct.
-	deferredCallType := b.ctx.StructType(valueTypes, false)
+	deferredCallType := b.ctx.StructType(values.types, false)
 	deferredCall := llvm.ConstNull(deferredCallType)
-	for i, value := range values {
+	for i, value := range values.values {
 		deferredCall = b.CreateInsertValue(deferredCall, value, i, "")
 	}
 
@@ -594,19 +615,11 @@ func (b *builder) createRunDefers() {
 				valueTypes = append(valueTypes, b.dataPtrType, b.dataPtrType)
 			}
 
-			for _, arg := range callback.Args {
-				valueTypes = append(valueTypes, b.getLLVMType(arg.Type()))
-			}
+			valueTypes = b.appendStoredValueTypes(valueTypes, callback.Args, false)
 
 			// Extract the params from the struct (including receiver).
-			forwardParams := []llvm.Value{}
-			zero := llvm.ConstInt(b.ctx.Int32Type(), 0, false)
 			deferredCallType := b.ctx.StructType(valueTypes, false)
-			for i := 2; i < len(valueTypes); i++ {
-				gep := b.CreateInBoundsGEP(deferredCallType, deferData, []llvm.Value{zero, llvm.ConstInt(b.ctx.Int32Type(), uint64(i), false)}, "gep")
-				forwardParam := b.CreateLoad(valueTypes[i], gep, "param")
-				forwardParams = append(forwardParams, forwardParam)
-			}
+			forwardParams := b.loadDeferredCallParams(deferredCallType, deferData)
 
 			var fnPtr llvm.Value
 			var fnType llvm.Type
@@ -635,6 +648,7 @@ func (b *builder) createRunDefers() {
 				// with a strict calling convention.
 				forwardParams = append(forwardParams, llvm.Undef(b.dataPtrType))
 			}
+			forwardParams = b.prependIndirectResult(callback.Signature(), false, forwardParams, "defer.result")
 
 			b.createCall(fnType, fnPtr, forwardParams, "")
 
@@ -643,27 +657,21 @@ func (b *builder) createRunDefers() {
 
 			// Get the real defer struct type and cast to it.
 			valueTypes := []llvm.Type{b.uintptrType, b.dataPtrType}
-			for _, param := range getParams(callback.Signature) {
-				valueTypes = append(valueTypes, b.getLLVMType(param.Type()))
-			}
+			exported := b.getFunctionInfo(callback).exported
+			valueTypes = b.appendStoredParamTypes(valueTypes, getParams(callback.Signature), exported)
 			deferredCallType := b.ctx.StructType(valueTypes, false)
 
 			// Extract the params from the struct.
-			forwardParams := []llvm.Value{}
-			zero := llvm.ConstInt(b.ctx.Int32Type(), 0, false)
-			for i := range getParams(callback.Signature) {
-				gep := b.CreateInBoundsGEP(deferredCallType, deferData, []llvm.Value{zero, llvm.ConstInt(b.ctx.Int32Type(), uint64(i+2), false)}, "gep")
-				forwardParam := b.CreateLoad(valueTypes[i+2], gep, "param")
-				forwardParams = append(forwardParams, forwardParam)
-			}
+			forwardParams := b.loadDeferredCallParams(deferredCallType, deferData)
 
 			// Plain TinyGo functions add some extra parameters to implement async functionality and function receivers.
 			// These parameters should not be supplied when calling into an external C/ASM function.
-			if !b.getFunctionInfo(callback).exported {
+			if !exported {
 				// Add the context parameter. We know it is ignored by the receiving
 				// function, but we have to pass one anyway.
 				forwardParams = append(forwardParams, llvm.Undef(b.dataPtrType))
 			}
+			forwardParams = b.prependIndirectResult(callback.Signature, exported, forwardParams, "defer.result")
 
 			// Call real function.
 			fnType, fn := b.getFunction(callback)
@@ -673,24 +681,16 @@ func (b *builder) createRunDefers() {
 			// Get the real defer struct type and cast to it.
 			fn := callback.Fn.(*ssa.Function)
 			valueTypes := []llvm.Type{b.uintptrType, b.dataPtrType}
-			params := fn.Signature.Params()
-			for v := range params.Variables() {
-				valueTypes = append(valueTypes, b.getLLVMType(v.Type()))
-			}
+			valueTypes = b.appendStoredParamTypes(valueTypes, getParams(fn.Signature), false)
 			valueTypes = append(valueTypes, b.dataPtrType) // closure
 			deferredCallType := b.ctx.StructType(valueTypes, false)
 
 			// Extract the params from the struct.
-			forwardParams := []llvm.Value{}
-			zero := llvm.ConstInt(b.ctx.Int32Type(), 0, false)
-			for i := 2; i < len(valueTypes); i++ {
-				gep := b.CreateInBoundsGEP(deferredCallType, deferData, []llvm.Value{zero, llvm.ConstInt(b.ctx.Int32Type(), uint64(i), false)}, "")
-				forwardParam := b.CreateLoad(valueTypes[i], gep, "param")
-				forwardParams = append(forwardParams, forwardParam)
-			}
+			forwardParams := b.loadDeferredCallParams(deferredCallType, deferData)
 
 			// Call deferred function.
 			fnType, llvmFn := b.getFunction(fn)
+			forwardParams = b.prependIndirectResult(fn.Signature, false, forwardParams, "defer.result")
 			b.createCall(fnType, llvmFn, forwardParams, "")
 		case *ssa.Builtin:
 			db := b.deferBuiltinFuncs[callback]
@@ -707,13 +707,7 @@ func (b *builder) createRunDefers() {
 			deferredCallType := b.ctx.StructType(valueTypes, false)
 
 			// Extract the params from the struct.
-			var argValues []llvm.Value
-			zero := llvm.ConstInt(b.ctx.Int32Type(), 0, false)
-			for i := 0; i < params.Len(); i++ {
-				gep := b.CreateInBoundsGEP(deferredCallType, deferData, []llvm.Value{zero, llvm.ConstInt(b.ctx.Int32Type(), uint64(i+2), false)}, "gep")
-				forwardParam := b.CreateLoad(valueTypes[i+2], gep, "param")
-				argValues = append(argValues, forwardParam)
-			}
+			argValues := b.loadDeferredCallParams(deferredCallType, deferData)
 
 			_, err := b.createBuiltin(db.argTypes, argValues, db.callName, db.pos)
 			if err != nil {
diff --git a/compiler/func.go b/compiler/func.go
index ed5808c72f..260ff07da0 100644
--- a/compiler/func.go
+++ b/compiler/func.go
@@ -10,6 +10,91 @@ import (
 	"tinygo.org/x/go-llvm"
 )
 
+// LLVM recursively expands each struct field and array element in parameters
+// and results into separate values. It gets very slow with too many values, so
+// pass larger aggregates indirectly before LLVM expands them.
+const maxDirectAggregateValues = 1024
+
+func (c *compilerContext) getLLVMResultType(sig *types.Signature) llvm.Type {
+	switch sig.Results().Len() {
+	case 0:
+		return c.ctx.VoidType()
+	case 1:
+		return c.getLLVMType(sig.Results().At(0).Type())
+	default:
+		results := make([]llvm.Type, sig.Results().Len())
+		for i := range results {
+			results[i] = c.getLLVMType(sig.Results().At(i).Type())
+		}
+		return c.ctx.StructType(results, false)
+	}
+}
+
+func (c *compilerContext) hasIndirectResult(sig *types.Signature) (llvm.Type, bool) {
+	resultType := c.getLLVMResultType(sig)
+	return resultType, c.isIndirectAggregate(resultType)
+}
+
+func (c *compilerContext) isIndirectAggregate(typ llvm.Type) bool {
+	switch typ.TypeKind() {
+	case llvm.ArrayTypeKind, llvm.StructTypeKind:
+		_, exceeded := aggregateValueCount(typ, 0)
+		return exceeded
+	default:
+		return false
+	}
+}
+
+func aggregateValueCount(typ llvm.Type, count uint64) (uint64, bool) {
+	switch typ.TypeKind() {
+	case llvm.ArrayTypeKind:
+		length := uint64(typ.ArrayLength())
+		if length == 0 {
+			return count, false
+		}
+		elementCount, exceeded := aggregateValueCount(typ.ElementType(), 0)
+		if exceeded {
+			return count, true
+		}
+		if elementCount != 0 && length > (maxDirectAggregateValues-count)/elementCount {
+			return count, true
+		}
+		return count + length*elementCount, false
+	case llvm.StructTypeKind:
+		for _, field := range typ.StructElementTypes() {
+			var exceeded bool
+			count, exceeded = aggregateValueCount(field, count)
+			if exceeded {
+				return count, true
+			}
+		}
+		return count, false
+	default:
+		count++
+		return count, count > maxDirectAggregateValues
+	}
+}
+
+func isLLVMValueType(typ types.Type) bool {
+	switch typ := typ.Underlying().(type) {
+	case *types.Basic:
+		return typ.Kind() != types.Invalid
+	case *types.Array:
+		return isLLVMValueType(typ.Elem())
+	case *types.Struct:
+		for field := range typ.Fields() {
+			if !isLLVMValueType(field.Type()) {
+				return false
+			}
+		}
+		return true
+	case *types.Chan, *types.Interface, *types.Map, *types.Pointer, *types.Signature, *types.Slice:
+		return true
+	default:
+		return false
+	}
+}
+
 // createFuncValue creates a function value from a raw function pointer with no
 // context.
 func (b *builder) createFuncValue(funcPtr, context llvm.Value, sig *types.Signature) llvm.Value {
@@ -48,28 +133,18 @@ func (c *compilerContext) getFuncType(typ *types.Signature) llvm.Type {
 
 // getLLVMFunctionType returns a LLVM function type for a given signature.
 func (c *compilerContext) getLLVMFunctionType(typ *types.Signature) llvm.Type {
-	// Get the return type.
-	var returnType llvm.Type
-	switch typ.Results().Len() {
-	case 0:
-		// No return values.
-		returnType = c.ctx.VoidType()
-	case 1:
-		// Just one return value.
-		returnType = c.getLLVMType(typ.Results().At(0).Type())
-	default:
-		// Multiple return values. Put them together in a struct.
-		// This appears to be the common way to handle multiple return values in
-		// LLVM.
-		members := make([]llvm.Type, typ.Results().Len())
-		for i := 0; i < typ.Results().Len(); i++ {
-			members[i] = c.getLLVMType(typ.Results().At(i).Type())
-		}
-		returnType = c.ctx.StructType(members, false)
-	}
+	returnType, indirectResult := c.hasIndirectResult(typ)
 
 	// Get the parameter types.
 	var paramTypes []llvm.Type
+	if indirectResult {
+		// LLVM expands aggregate returns into scalar leaves before deciding
+		// whether to pass them indirectly, so a large IR return can exhaust
+		// memory. Returning void avoids that expansion and cannot be demoted
+		// again. Keep the result pointer first so the context remains last.
+		paramTypes = append(paramTypes, c.dataPtrType)
+		returnType = c.ctx.VoidType()
+	}
 	if typ.Recv() != nil {
 		recv := c.getLLVMType(typ.Recv().Type())
 		if recv.StructName() == "runtime._interface" {
diff --git a/compiler/goroutine.go b/compiler/goroutine.go
index b3e02c2002..26d489a3a4 100644
--- a/compiler/goroutine.go
+++ b/compiler/goroutine.go
@@ -47,20 +47,16 @@ func (b *builder) createGo(instr *ssa.Go) {
 		return
 	}
 
-	// Get all function parameters to pass to the goroutine.
 	var params []llvm.Value
-	for _, param := range instr.Call.Args {
-		params = append(params, b.expandFormalParam(b.getValue(param, getPos(instr)))...)
-	}
-
 	var prefix string
 	var funcPtr llvm.Value
 	var funcType llvm.Type
+	var context llvm.Value
 	hasContext := false
+	exported := false
 	if callee := instr.Call.StaticCallee(); callee != nil {
 		// Static callee is known. This makes it easier to start a new
 		// goroutine.
-		var context llvm.Value
 		switch value := instr.Call.Value.(type) {
 		case *ssa.Function:
 			// Goroutine call is regular function call. No context is necessary.
@@ -73,10 +69,10 @@ func (b *builder) createGo(instr *ssa.Go) {
 			panic("StaticCallee returned an unexpected value")
 		}
 		if !context.IsNil() {
-			params = append(params, context) // context parameter
 			hasContext = true
 		}
 		funcType, funcPtr = b.getFunction(callee)
+		exported = b.getFunctionInfo(callee).exported
 	} else if instr.Call.IsInvoke() {
 		// This is a method call on an interface value.
 		itf := b.getValue(instr.Call.Value, getPos(instr))
@@ -84,22 +80,31 @@ func (b *builder) createGo(instr *ssa.Go) {
 		itfValue := b.CreateExtractValue(itf, 1, "")
 		funcPtr = b.getInvokeFunction(&instr.Call)
 		funcType = funcPtr.GlobalValueType()
-		params = append([]llvm.Value{itfValue}, params...) // start with receiver
-		params = append(params, itfTypeCode)               // end with typecode
+		params = append(params, itfValue)
+		context = itfTypeCode
 	} else {
 		// This is a function pointer.
 		// At the moment, two extra params are passed to the newly started
 		// goroutine:
 		//   * The function context, for closures.
 		//   * The function pointer (for tasks).
-		var context llvm.Value
 		funcPtr, context = b.decodeFuncValue(b.getValue(instr.Call.Value, getPos(instr)))
 		funcType = b.getLLVMFunctionType(instr.Call.Value.Type().Underlying().(*types.Signature))
-		params = append(params, context, funcPtr)
 		hasContext = true
 		prefix = b.getFunctionInfo(b.fn).linkName
 	}
 
+	for _, param := range instr.Call.Args {
+		params = append(params, b.getGoroutineCallArgument(param, exported)...)
+	}
+	if !context.IsNil() {
+		params = append(params, context)
+	}
+	if hasContext && instr.Call.StaticCallee() == nil {
+		params = append(params, funcPtr)
+	}
+	params = b.prependIndirectResult(instr.Call.Signature(), exported, params, "go.result")
+
 	paramBundle := b.emitPointerPack(params, instr.Pos())
 	var stackSize llvm.Value
 	callee := b.createGoroutineStartWrapper(funcType, funcPtr, prefix, hasContext, false, instr.Pos())
@@ -122,6 +127,15 @@ func (b *builder) createGo(instr *ssa.Go) {
 	b.createCall(fnType, start, []llvm.Value{callee, paramBundle, stackSize, llvm.Undef(b.dataPtrType)}, "")
 }
 
+func (b *builder) getGoroutineCallArgument(value ssa.Value, exported bool) []llvm.Value {
+	typ := b.getLLVMType(value.Type())
+	arg := b.getCallArgument(value, exported)
+	if b.isIndirectParam(typ, exported) {
+		return []llvm.Value{b.copyToIndirectStorage(arg, typ, "go.param")}
+	}
+	return b.expandFormalParam(arg)
+}
+
 // Create an exported wrapper function for functions with the //go:wasmexport
 // pragma. This wrapper function is quite complex when the scheduler is enabled:
 // it needs to start a new goroutine each time the exported function is called.
diff --git a/compiler/interface.go b/compiler/interface.go
index bb427e6e54..631a131f62 100644
--- a/compiler/interface.go
+++ b/compiler/interface.go
@@ -85,6 +85,10 @@ const (
 // An interface value is a {typecode, value} tuple named runtime._interface.
 func (b *builder) createMakeInterface(val llvm.Value, typ types.Type, pos token.Pos) llvm.Value {
 	itfValue := b.emitPointerPack([]llvm.Value{val}, pos)
+	return b.createMakeInterfaceFromPointer(itfValue, typ)
+}
+
+func (b *builder) createMakeInterfaceFromPointer(itfValue llvm.Value, typ types.Type) llvm.Value {
 	itfType := b.getTypeCode(typ)
 	itf := llvm.Undef(b.getLLVMRuntimeType("_interface"))
 	itf = b.CreateInsertValue(itf, itfType, 0, "")
@@ -98,9 +102,16 @@ func (b *builder) createMakeInterface(val llvm.Value, typ types.Type, pos token.
 // doesn't match the underlying type of the interface.
 func (b *builder) extractValueFromInterface(itf llvm.Value, llvmType llvm.Type) llvm.Value {
 	valuePtr := b.CreateExtractValue(itf, 1, "typeassert.value.ptr")
+	if b.isIndirectAggregate(llvmType) {
+		return valuePtr
+	}
 	return b.emitPointerUnpack(valuePtr, []llvm.Type{llvmType})[0]
 }
 
+func (b *builder) extractValuePointerFromInterface(itf llvm.Value) llvm.Value {
+	return b.CreateExtractValue(itf, 1, "typeassert.value.ptr")
+}
+
 func (c *compilerContext) pkgPathPtr(pkgpath string) llvm.Value {
 	pkgpathName := "reflect/types.type.pkgpath.empty"
 	if pkgpath != "" {
@@ -1067,6 +1078,21 @@ func (b *builder) createTypeAssert(expr *ssa.TypeAssert) llvm.Value {
 	if expr.CommaOk {
 		nextBlock := b.insertBasicBlock("typeassert.next")
 		b.currentBlockInfo.exit = nextBlock
+		if b.isIndirectAggregate(assertedType) {
+			resultType := b.getLLVMType(expr.Type())
+			result := b.createIndirectStorage(resultType, "typeassert.result")
+			b.zeroIndirectStorage(result, resultType)
+			b.CreateCondBr(commaOk, okBlock, nextBlock)
+
+			b.SetInsertPointAtEnd(okBlock)
+			valuePtr := b.extractValuePointerFromInterface(itf)
+			b.copyIndirectAggregate(b.CreateStructGEP(resultType, result, 0, ""), valuePtr, assertedType)
+			b.CreateBr(nextBlock)
+
+			b.SetInsertPointAtEnd(nextBlock)
+			b.CreateStore(commaOk, b.CreateStructGEP(resultType, result, 1, ""))
+			return result
+		}
 		b.CreateCondBr(commaOk, okBlock, nextBlock)
 
 		// Retrieve the value from the interface if the type assert was
@@ -1207,6 +1233,9 @@ func (c *compilerContext) getInvokeFunction(instr *ssa.CallCommon) llvm.Value {
 		llvmFn = llvm.AddFunction(c.mod, fnName, llvmFnType)
 		c.addStandardDeclaredAttributes(llvmFn)
 		llvmFn.AddFunctionAttr(c.ctx.CreateStringAttribute("tinygo-invoke", c.getMethodSignatureName(instr.Method)))
+		if _, indirect := c.hasIndirectResult(sig); indirect {
+			llvmFn.AddFunctionAttr(c.ctx.CreateStringAttribute("tinygo-indirect-result", "true"))
+		}
 		methods := c.getMethodsString(instr.Value.Type().Underlying().(*types.Interface))
 		llvmFn.AddFunctionAttr(c.ctx.CreateStringAttribute("tinygo-methods", methods))
 	}
@@ -1247,6 +1276,7 @@ func (c *compilerContext) getInterfaceInvokeWrapper(fn *ssa.Function, llvmFnType
 	// Get the expanded receiver type.
 	receiverType := c.getLLVMType(fn.Signature.Recv().Type())
 	var expandedReceiverType []llvm.Type
+	receiverIndirect := c.isIndirectAggregate(receiverType)
 	for _, info := range c.expandFormalParamType(receiverType, "", nil) {
 		expandedReceiverType = append(expandedReceiverType, info.llvmType)
 	}
@@ -1261,7 +1291,13 @@ func (c *compilerContext) getInterfaceInvokeWrapper(fn *ssa.Function, llvmFnType
 	}
 
 	// create wrapper function
-	paramTypes := append([]llvm.Type{c.dataPtrType}, llvmFnType.ParamTypes()[len(expandedReceiverType):]...)
+	resultOffset := 0
+	if _, indirect := c.hasIndirectResult(fn.Signature); indirect {
+		resultOffset = 1
+	}
+	paramTypes := append([]llvm.Type{}, llvmFnType.ParamTypes()[:resultOffset]...)
+	paramTypes = append(paramTypes, c.dataPtrType)
+	paramTypes = append(paramTypes, llvmFnType.ParamTypes()[resultOffset+len(expandedReceiverType):]...)
 	wrapFnType := llvm.FunctionType(llvmFnType.ReturnType(), paramTypes, false)
 	wrapper = llvm.AddFunction(c.mod, wrapperName, wrapFnType)
 	c.addStandardAttributes(wrapper)
@@ -1287,8 +1323,15 @@ func (c *compilerContext) getInterfaceInvokeWrapper(fn *ssa.Function, llvmFnType
 	block := b.ctx.AddBasicBlock(wrapper, "entry")
 	b.SetInsertPointAtEnd(block)
 
-	receiverValue := b.emitPointerUnpack(wrapper.Param(0), []llvm.Type{receiverType})[0]
-	params := append(b.expandFormalParam(receiverValue), wrapper.Params()[1:]...)
+	params := append([]llvm.Value{}, wrapper.Params()[:resultOffset]...)
+	receiverParam := wrapper.Param(resultOffset)
+	if receiverIndirect {
+		params = append(params, receiverParam)
+	} else {
+		receiverValue := b.emitPointerUnpack(receiverParam, []llvm.Type{receiverType})[0]
+		params = append(params, b.expandFormalParam(receiverValue)...)
+	}
+	params = append(params, wrapper.Params()[resultOffset+1:]...)
 	if llvmFnType.ReturnType().TypeKind() == llvm.VoidTypeKind {
 		b.CreateCall(llvmFnType, llvmFn, params, "")
 		b.CreateRetVoid()
diff --git a/compiler/map.go b/compiler/map.go
index 4f9ec66ea5..3481ae90ac 100644
--- a/compiler/map.go
+++ b/compiler/map.go
@@ -72,19 +72,20 @@ func (b *builder) getRuntimeFunctionValue(name string, sig *types.Signature) llv
 
 // createMapLookup returns the value in a map. It calls a runtime function
 // depending on the map key type to load the map value and its comma-ok value.
-func (b *builder) createMapLookup(keyType, valueType types.Type, m, key llvm.Value, commaOk bool, pos token.Pos) (llvm.Value, error) {
+func (b *builder) createMapLookup(keyType, valueType types.Type, m llvm.Value, key ssa.Value, commaOk bool, pos token.Pos) (llvm.Value, error) {
 	llvmValueType := b.getLLVMType(valueType)
 
 	// Allocate the memory for the resulting type. Do not zero this memory: it
 	// will be zeroed by the hashmap get implementation if the key is not
 	// present in the map.
-	mapValueAlloca, mapValueAllocaSize := b.createTemporaryAlloca(llvmValueType, "hashmap.value")
+	result := b.createRuntimeValueResult(llvmValueType, commaOk, false, "hashmap")
+	mapValueAlloca := result.valuePtr
 
 	// We need the map size (with type uintptr) to pass to the hashmap*Get
 	// functions. This is necessary because those *Get functions are valid on
 	// nil maps, and they'll need to zero the value pointer by that number of
 	// bytes.
-	mapValueSize := mapValueAllocaSize
+	mapValueSize := result.valueSize
 	if mapValueSize.Type().IntTypeWidth() > b.uintptrType.IntTypeWidth() {
 		mapValueSize = llvm.ConstTrunc(mapValueSize, b.uintptrType)
 	}
@@ -94,60 +95,46 @@ func (b *builder) createMapLookup(keyType, valueType types.Type, m, key llvm.Val
 	keyType = keyType.Underlying()
 	if t, ok := keyType.(*types.Basic); ok && t.Info()&types.IsString != 0 {
 		// key is a string
-		params := []llvm.Value{m, key, mapValueAlloca, mapValueSize}
+		params := []llvm.Value{m, b.getValue(key, getPos(key)), mapValueAlloca, mapValueSize}
 		commaOkValue = b.createRuntimeCall("hashmapStringGet", params, "")
 	} else {
 		// Key stored at actual type: either binary-comparable or with
 		// compiler-generated hash/equal.
-		mapKeyAlloca, mapKeySize := b.createTemporaryAlloca(key.Type(), "hashmap.key")
-		b.CreateStore(key, mapKeyAlloca)
-		params := []llvm.Value{m, mapKeyAlloca, mapValueAlloca, mapValueSize}
+		mapKey := b.getValueStorage(key, "hashmap.key")
+		params := []llvm.Value{m, mapKey.ptr, mapValueAlloca, mapValueSize}
 		fnName := "hashmapBinaryGet"
 		if !hashmapIsBinaryKey(keyType) {
 			fnName = "hashmapGenericGet"
 		}
 		commaOkValue = b.createRuntimeCall(fnName, params, "")
-		b.emitLifetimeEnd(mapKeyAlloca, mapKeySize)
+		b.endValueStorage(mapKey)
 	}
 
-	// Load the resulting value from the hashmap. The value is set to the zero
-	// value if the key doesn't exist in the hashmap.
-	mapValue := b.CreateLoad(llvmValueType, mapValueAlloca, "")
-	b.emitLifetimeEnd(mapValueAlloca, mapValueAllocaSize)
-
-	if commaOk {
-		tuple := llvm.Undef(b.ctx.StructType([]llvm.Type{llvmValueType, b.ctx.Int1Type()}, false))
-		tuple = b.CreateInsertValue(tuple, mapValue, 0, "")
-		tuple = b.CreateInsertValue(tuple, commaOkValue, 1, "")
-		return tuple, nil
-	} else {
-		return mapValue, nil
-	}
+	// The value is set to the zero value if the key doesn't exist.
+	return result.finish(b, commaOkValue, ""), nil
 }
 
 // createMapUpdate updates a map key to a given value, by creating an
 // appropriate runtime call.
-func (b *builder) createMapUpdate(keyType types.Type, m, key, value llvm.Value, pos token.Pos) {
-	valueAlloca, valueSize := b.createTemporaryAlloca(value.Type(), "hashmap.value")
-	b.CreateStore(value, valueAlloca)
+func (b *builder) createMapUpdate(keyType types.Type, m llvm.Value, key, value ssa.Value, pos token.Pos) {
+	storedValue := b.getValueStorage(value, "hashmap.value")
 	keyType = keyType.Underlying()
 	if t, ok := keyType.(*types.Basic); ok && t.Info()&types.IsString != 0 {
 		// key is a string
-		params := []llvm.Value{m, key, valueAlloca}
+		params := []llvm.Value{m, b.getValue(key, getPos(key)), storedValue.ptr}
 		b.createRuntimeInvoke("hashmapStringSet", params, "")
 	} else {
 		// Key stored at actual type.
-		keyAlloca, keySize := b.createTemporaryAlloca(key.Type(), "hashmap.key")
-		b.CreateStore(key, keyAlloca)
+		keyStorage := b.getValueStorage(key, "hashmap.key")
 		fnName := "hashmapBinarySet"
 		if !hashmapIsBinaryKey(keyType) {
 			fnName = "hashmapGenericSet"
 		}
-		params := []llvm.Value{m, keyAlloca, valueAlloca}
+		params := []llvm.Value{m, keyStorage.ptr, storedValue.ptr}
 		b.createRuntimeInvoke(fnName, params, "")
-		b.emitLifetimeEnd(keyAlloca, keySize)
+		b.endValueStorage(keyStorage)
 	}
-	b.emitLifetimeEnd(valueAlloca, valueSize)
+	b.endValueStorage(storedValue)
 }
 
 // createMapDelete deletes a key from a map by calling the appropriate runtime
diff --git a/compiler/symbol.go b/compiler/symbol.go
index 90dfc0d08b..944f74240e 100644
--- a/compiler/symbol.go
+++ b/compiler/symbol.go
@@ -79,24 +79,27 @@ func (c *compilerContext) getFunction(fn *ssa.Function) (llvm.Type, llvm.Value)
 		return llvmFn.GlobalValueType(), llvmFn
 	}
 
-	var retType llvm.Type
-	if fn.Signature.Results() == nil {
-		retType = c.ctx.VoidType()
-	} else if fn.Signature.Results().Len() == 1 {
-		retType = c.getLLVMType(fn.Signature.Results().At(0).Type())
-	} else {
-		results := make([]llvm.Type, 0, fn.Signature.Results().Len())
-		for v := range fn.Signature.Results().Variables() {
-			results = append(results, c.getLLVMType(v.Type()))
-		}
-		retType = c.ctx.StructType(results, false)
+	retType, indirectResult := c.hasIndirectResult(fn.Signature)
+	if info.exported {
+		indirectResult = false
 	}
 
 	var paramInfos []paramInfo
+	if indirectResult {
+		paramInfos = append(paramInfos, paramInfo{
+			llvmType: c.dataPtrType,
+			name:     "return",
+			elemSize: c.targetData.TypeAllocSize(retType),
+		})
+		retType = c.ctx.VoidType()
+	}
 	for _, param := range getParams(fn.Signature) {
 		paramType := c.getLLVMType(param.Type())
-		paramFragmentInfos := c.expandFormalParamType(paramType, param.Name(), param.Type())
-		paramInfos = append(paramInfos, paramFragmentInfos...)
+		if info.exported {
+			paramInfos = append(paramInfos, c.expandDirectFormalParamType(paramType, param.Name(), param.Type())...)
+		} else {
+			paramInfos = append(paramInfos, c.expandFormalParamType(paramType, param.Name(), param.Type())...)
+		}
 	}
 
 	// Add an extra parameter as the function context. This context is used in
@@ -106,12 +109,20 @@ func (c *compilerContext) getFunction(fn *ssa.Function) (llvm.Type, llvm.Value)
 	}
 
 	var paramTypes []llvm.Type
+	hasIndirectABI := indirectResult
 	for _, info := range paramInfos {
 		paramTypes = append(paramTypes, info.llvmType)
+		hasIndirectABI = hasIndirectABI || info.flags&paramIsIndirect != 0
 	}
 
 	fnType := llvm.FunctionType(retType, paramTypes, info.variadic)
 	llvmFn = llvm.AddFunction(c.mod, info.linkName, fnType)
+	if hasIndirectABI {
+		// Argument promotion only rewrites functions whose uses are all direct
+		// calls. Keep an address use so LLVM cannot reconstruct the large
+		// aggregate signature that this ABI exists to avoid.
+		llvmutil.AppendToGlobal(c.mod, "llvm.used", llvmFn)
+	}
 	if strings.HasPrefix(c.Triple, "wasm") {
 		// C functions without prototypes like this:
 		//   void foo();
diff --git a/compiler/testdata/large-optimized.go b/compiler/testdata/large-optimized.go
new file mode 100644
index 0000000000..91a0740fa2
--- /dev/null
+++ b/compiler/testdata/large-optimized.go
@@ -0,0 +1,20 @@
+package main
+
+type largeOptimizedValue [1025]byte
+
+type mixedLargeOptimizedValue struct {
+	value [1025]byte
+	any   any
+}
+
+func makeLargeOptimizedValue() largeOptimizedValue {
+	return largeOptimizedValue{}
+}
+
+func readLargeOptimizedValue(value largeOptimizedValue) byte {
+	return value[len(value)-1]
+}
+
+func readMixedLargeOptimizedValue(value mixedLargeOptimizedValue) byte {
+	return value.value[len(value.value)-1]
+}
diff --git a/compiler/testdata/large.go b/compiler/testdata/large.go
new file mode 100644
index 0000000000..5fc9cae847
--- /dev/null
+++ b/compiler/testdata/large.go
@@ -0,0 +1,120 @@
+package main
+
+type largeValue [1025]byte
+
+type largeStruct struct {
+	value [1025]byte
+	ptr   *byte
+}
+
+type largeInterface interface {
+	makeLargeValue() largeValue
+	readLargeValue(largeValue) byte
+}
+
+type largeReceiver largeValue
+
+func makeLargeValue(value byte) largeValue {
+	var result largeValue
+	result[len(result)-1] = value
+	return result
+}
+
+func makeZeroLargeValue() largeValue {
+	return largeValue{}
+}
+
+func passZeroLargeValue() byte {
+	return readLargeValue(largeValue{})
+}
+
+func readLargeValue(value largeValue) byte {
+	return value[len(value)-1]
+}
+
+func useLargeValue() byte {
+	return readLargeValue(makeLargeValue(42))
+}
+
+func useLargeFunctionValue(fn func(largeValue) byte) byte {
+	return fn(makeLargeValue(42))
+}
+
+func (receiver largeReceiver) makeLargeValue() largeValue {
+	return largeValue(receiver)
+}
+
+func (receiver largeReceiver) readLargeValue(value largeValue) byte {
+	return value[len(value)-1]
+}
+
+func useLargeInterface(value largeInterface) byte {
+	return value.readLargeValue(value.makeLargeValue())
+}
+
+func deferLargeValue(value largeValue) {
+	defer readLargeValue(value)
+}
+
+func goLargeValue(value largeValue) {
+	go readLargeValue(value)
+}
+
+func makeLargeResults(value byte) (largeValue, byte) {
+	return makeLargeValue(value), value
+}
+
+func makeTwoLargeResults(value byte) (largeValue, largeValue) {
+	return makeLargeValue(value), makeLargeValue(value + 1)
+}
+
+func makeMixedLargeResults(value byte) (largeValue, byte, largeValue) {
+	return makeLargeValue(value), value + 1, makeLargeValue(value + 2)
+}
+
+func chooseLargeValue(flag bool) largeValue {
+	value := makeLargeValue(1)
+	if flag {
+		value = makeLargeValue(42)
+	}
+	return value
+}
+
+func makePointerLargeValue(value *byte) largeStruct {
+	return largeStruct{ptr: value}
+}
+
+func assertLargeValue(value any) byte {
+	large, ok := value.(largeValue)
+	if !ok {
+		return 0
+	}
+	return large[len(large)-1]
+}
+
+func useLargeMap(key, value largeValue) byte {
+	values := map[largeValue]largeValue{key: value}
+	result, ok := values[key]
+	if !ok {
+		return 0
+	}
+	return result[len(result)-1]
+}
+
+func useLargeChannel(ch chan largeValue, value largeValue) byte {
+	ch <- value
+	result, ok := <-ch
+	if !ok {
+		return 0
+	}
+	return result[len(result)-1]
+}
+
+func selectLargeChannel(ch chan largeValue, value largeValue) byte {
+	select {
+	case ch <- value:
+		return 0
+	case result := <-ch:
+		return result[len(result)-1]
+	}
+}
diff --git a/compiler/testdata/large.ll b/compiler/testdata/large.ll
new file mode 100644
index 0000000000..27da846060
--- /dev/null
+++ b/compiler/testdata/large.ll
@@ -0,0 +1,498 @@
+; ModuleID = 'large.go'
+source_filename = "large.go"
+target datalayout = "e-m:e-p:32:32-p10:8:8-p20:8:8-i64:64-i128:128-n32:64-S128-ni:1:10:20"
+target triple = "wasm32-unknown-wasi"
+
+%runtime._string = type { ptr, i32 }
+%runtime.channelOp = type { ptr, ptr, i32, ptr }
+%runtime.chanSelectState = type { ptr, ptr }
+
+@"runtime/gc.layout:258-000000000000000000000000000000000000000000000000000000000000000002" = linkonce_odr unnamed_addr constant { i32, [33 x i8] } { i32 258, [33 x i8] c"\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\02" }
+@"reflect/types.typeid:named:main.largeValue" = external constant i8
+@llvm.used = appending global [15 x ptr] [ptr @"(main.largeReceiver).makeLargeValue", ptr @"(main.largeReceiver).readLargeValue", ptr @main.makeLargeValue, ptr @main.makeZeroLargeValue, ptr @main.readLargeValue, ptr @main.deferLargeValue, ptr @main.goLargeValue, ptr @main.makeLargeResults, ptr @main.makeTwoLargeResults, ptr @main.makeMixedLargeResults, ptr @main.chooseLargeValue, ptr @main.makePointerLargeValue, ptr @main.useLargeMap, ptr @main.useLargeChannel, ptr @main.selectLargeChannel]
+@"main$string" = internal unnamed_addr constant [31 x i8] c"blocking select matched no case", align 1
+@"main$pack" = internal unnamed_addr constant { %runtime._string } { %runtime._string { ptr @"main$string", i32 31 } }
+@"reflect/types.type:basic:string" = linkonce_odr constant { i8, ptr } { i8 81, ptr @"reflect/types.type:pointer:basic:string" }, align 4
+@"reflect/types.type:pointer:basic:string" = linkonce_odr constant { i8, i16, ptr } { i8 -43, i16 0, ptr @"reflect/types.type:basic:string" }, align 4
+
+declare void @runtime.trackPointer(ptr readonly captures(none), ptr, ptr) #0
+
+; Function Attrs: nounwind
+define hidden void @main.init(ptr %context) unnamed_addr #1 {
+entry:
+  ret void
+}
+
+; Function Attrs: nounwind
+define hidden void @"(main.largeReceiver).makeLargeValue"(ptr dereferenceable_or_null(1025) %return, ptr readonly dereferenceable_or_null(1025) %receiver, ptr %context) unnamed_addr #1 {
+entry:
+  call void @llvm.memcpy.p0.p0.i32(ptr noundef nonnull align 1 dereferenceable(1025) %return, ptr noundef nonnull align 1 dereferenceable(1025) %receiver, i32 1025, i1 false)
+  ret void
+}
+
+; Function Attrs: nocallback nofree nounwind willreturn memory(argmem: readwrite)
+declare void @llvm.memcpy.p0.p0.i32(ptr noalias writeonly captures(none), ptr noalias readonly captures(none), i32, i1 immarg) #2
+
+; Function Attrs: nounwind
+define hidden i8 @"(main.largeReceiver).readLargeValue"(ptr readonly dereferenceable_or_null(1025) %receiver, ptr readonly dereferenceable_or_null(1025) %value, ptr %context) unnamed_addr #1 {
+entry:
+  %stackalloc = alloca i8, align 1
+  %value1 = call align 1 dereferenceable(1025) ptr @runtime.alloc(i32 1025, ptr nonnull inttoptr (i32 3 to ptr), ptr undef) #9
+  call void @runtime.trackPointer(ptr nonnull %value1, ptr nonnull %stackalloc, ptr undef) #9
+  call void @llvm.memcpy.p0.p0.i32(ptr noundef nonnull align 1 dereferenceable(1025) %value1, ptr noundef nonnull align 1 dereferenceable(1025) %value, i32 1025, i1 false)
+  %0 = getelementptr inbounds nuw i8, ptr %value1, i32 1024
+  %1 = load i8, ptr %0, align 1
+  ret i8 %1
+}
+
+; Function Attrs: allockind("alloc,zeroed") allocsize(0)
+declare noalias nonnull ptr @runtime.alloc(i32, ptr, ptr) #3
+
+; Function Attrs: nounwind
+define hidden void @main.makeLargeValue(ptr dereferenceable_or_null(1025) %return, i8 %value, ptr %context) unnamed_addr #1 {
+entry:
+  %stackalloc = alloca i8, align 1
+  %result = call align 1 dereferenceable(1025) ptr @runtime.alloc(i32 1025, ptr nonnull inttoptr (i32 3 to ptr), ptr undef) #9
+  call void @runtime.trackPointer(ptr nonnull %result, ptr nonnull %stackalloc, ptr undef) #9
+  %0 = getelementptr inbounds nuw i8, ptr %result, i32 1024
+  store i8 %value, ptr %0, align 1
+  %1 = call align 1 dereferenceable(1025) ptr @runtime.alloc(i32 1025, ptr nonnull inttoptr (i32 3 to ptr), ptr undef) #9
+  call void @runtime.trackPointer(ptr nonnull %1, ptr nonnull %stackalloc, ptr undef) #9
+  call void @llvm.memcpy.p0.p0.i32(ptr noundef nonnull align 1 dereferenceable(1025) %1, ptr noundef nonnull align 1 dereferenceable(1025) %result, i32 1025, i1 false)
+  call void @llvm.memcpy.p0.p0.i32(ptr noundef nonnull align 1 dereferenceable(1025) %return, ptr noundef nonnull align 1 dereferenceable(1025) %1, i32 1025, i1 false)
+  ret void
+}
+
+; Function Attrs: nounwind
+define hidden void @main.makeZeroLargeValue(ptr dereferenceable_or_null(1025) %return, ptr %context) unnamed_addr #1 {
+entry:
+  store [1025 x i8] zeroinitializer, ptr %return, align 1
+  ret void
+}
+
+; Function Attrs: nounwind
+define hidden i8 @main.passZeroLargeValue(ptr %context) unnamed_addr #1 {
+entry:
+  %stackalloc = alloca i8, align 1
+  %"main.largeValue{}:main.largeValue" = call align 1 dereferenceable(1025) ptr @runtime.alloc(i32 1025, ptr nonnull inttoptr (i32 3 to ptr), ptr undef) #9
+  call void @runtime.trackPointer(ptr nonnull %"main.largeValue{}:main.largeValue", ptr nonnull %stackalloc, ptr undef) #9
+  store [1025 x i8] zeroinitializer, ptr %"main.largeValue{}:main.largeValue", align 1
+  %0 = call i8 @main.readLargeValue(ptr nonnull %"main.largeValue{}:main.largeValue", ptr undef)
+  ret i8 %0
+}
+
+; Function Attrs: nounwind
+define hidden i8 @main.readLargeValue(ptr readonly dereferenceable_or_null(1025) %value, ptr %context) unnamed_addr #1 {
+entry:
+  %stackalloc = alloca i8, align 1
+  %value1 = call align 1 dereferenceable(1025) ptr @runtime.alloc(i32 1025, ptr nonnull inttoptr (i32 3 to ptr), ptr undef) #9
+  call void @runtime.trackPointer(ptr nonnull %value1, ptr nonnull %stackalloc, ptr undef) #9
+  call void @llvm.memcpy.p0.p0.i32(ptr noundef nonnull align 1 dereferenceable(1025) %value1, ptr noundef nonnull align 1 dereferenceable(1025) %value, i32 1025, i1 false)
+  %0 = getelementptr inbounds nuw i8, ptr %value1, i32 1024
+  %1 = load i8, ptr %0, align 1
+  ret i8 %1
+}
+
+; Function Attrs: nounwind
+define hidden i8 @main.useLargeValue(ptr %context) unnamed_addr #1 {
+entry:
+  %stackalloc = alloca i8, align 1
+  %call.result = call align 1 dereferenceable(1025) ptr @runtime.alloc(i32 1025, ptr nonnull inttoptr (i32 3 to ptr), ptr undef) #9
+  call void @runtime.trackPointer(ptr nonnull %call.result, ptr nonnull %stackalloc, ptr undef) #9
+  call void @main.makeLargeValue(ptr nonnull %call.result, i8 42, ptr undef)
+  %0 = call i8 @main.readLargeValue(ptr nonnull %call.result, ptr undef)
+  ret i8 %0
+}
+
+; Function Attrs: nounwind
+define hidden i8 @main.useLargeFunctionValue(ptr %fn.context, ptr %fn.funcptr, ptr %context) unnamed_addr #1 {
+entry:
+  %stackalloc = alloca i8, align 1
+  %call.result = call align 1 dereferenceable(1025) ptr @runtime.alloc(i32 1025, ptr nonnull inttoptr (i32 3 to ptr), ptr undef) #9
+  call void @runtime.trackPointer(ptr nonnull %call.result, ptr nonnull %stackalloc, ptr undef) #9
+  call void @main.makeLargeValue(ptr nonnull %call.result, i8 42, ptr undef)
+  %0 = icmp eq ptr %fn.funcptr, null
+  br i1 %0, label %fpcall.throw, label %fpcall.next
+
+fpcall.next:                                      ; preds = %entry
+  %1 = call i8 %fn.funcptr(ptr nonnull %call.result, ptr %fn.context) #9
+  ret i8 %1
+
+fpcall.throw:                                     ; preds = %entry
+  call void @runtime.nilPanic(ptr undef) #9
+  unreachable
+}
+
+declare void @runtime.nilPanic(ptr) #0
+
+; Function Attrs: nounwind
+define hidden i8 @main.useLargeInterface(ptr %value.typecode, ptr %value.value, ptr %context) unnamed_addr #1 {
+entry:
+  %stackalloc = alloca i8, align 1
+  %call.result = call align 1 dereferenceable(1025) ptr @runtime.alloc(i32 1025, ptr nonnull inttoptr (i32 3 to ptr), ptr undef) #9
+  call void @runtime.trackPointer(ptr nonnull %call.result, ptr nonnull %stackalloc, ptr undef) #9
+  call void @"interface:{main.makeLargeValue:func:{}{named:main.largeValue},main.readLargeValue:func:{named:main.largeValue}{basic:uint8}}.makeLargeValue$invoke"(ptr nonnull %call.result, ptr %value.value, ptr %value.typecode, ptr undef) #9
+  %0 = call i8 @"interface:{main.makeLargeValue:func:{}{named:main.largeValue},main.readLargeValue:func:{named:main.largeValue}{basic:uint8}}.readLargeValue$invoke"(ptr %value.value, ptr nonnull %call.result, ptr %value.typecode, ptr undef) #9
+  ret i8 %0
+}
+
+declare void @"interface:{main.makeLargeValue:func:{}{named:main.largeValue},main.readLargeValue:func:{named:main.largeValue}{basic:uint8}}.makeLargeValue$invoke"(ptr, ptr, ptr, ptr) #4
+
+declare i8 @"interface:{main.makeLargeValue:func:{}{named:main.largeValue},main.readLargeValue:func:{named:main.largeValue}{basic:uint8}}.readLargeValue$invoke"(ptr, ptr, ptr, ptr) #5
+
+; Function Attrs: nounwind
+define hidden void @main.deferLargeValue(ptr readonly dereferenceable_or_null(1025) %value, ptr %context) unnamed_addr #1 {
+entry:
+  %defer.alloca = alloca { i32, ptr, ptr }, align 8
+  %deferPtr = alloca ptr, align 4
+  store ptr null, ptr %deferPtr, align 4
+  %stackalloc = alloca i8, align 1
+  call void @runtime.trackPointer(ptr nonnull %defer.alloca, ptr nonnull %stackalloc, ptr undef) #9
+  store i32 0, ptr %defer.alloca, align 4
+  %defer.alloca.repack1 = getelementptr inbounds nuw i8, ptr %defer.alloca, i32 4
+  store ptr null, ptr %defer.alloca.repack1, align 4
+  %defer.alloca.repack3 = getelementptr inbounds nuw i8, ptr %defer.alloca, i32 8
+  store ptr %value, ptr %defer.alloca.repack3, align 4
+  store ptr %defer.alloca, ptr %deferPtr, align 4
+  br label %rundefers.block
+
+rundefers.after:                                  ; preds = %rundefers.end
+  ret void
+
+rundefers.block:                                  ; preds = %entry
+  br label %rundefers.loophead
+
+rundefers.loophead:                               ; preds = %rundefers.callback0, %rundefers.block
+  %0 = load ptr, ptr %deferPtr, align 4
+  %stackIsNil = icmp eq ptr %0, null
+  br i1 %stackIsNil, label %rundefers.end, label %rundefers.loop
+
+rundefers.loop:                                   ; preds = %rundefers.loophead
+  %stack.next.gep = getelementptr inbounds nuw i8, ptr %0, i32 4
+  %stack.next = load ptr, ptr %stack.next.gep, align 4
+  store ptr %stack.next, ptr %deferPtr, align 4
+  %callback = load i32, ptr %0, align 4
+  switch i32 %callback, label %rundefers.default [
+    i32 0, label %rundefers.callback0
+  ]
+
+rundefers.callback0:                              ; preds = %rundefers.loop
+  %gep = getelementptr inbounds nuw i8, ptr %0, i32 8
+  %param = load ptr, ptr %gep, align 4
+  %1 = call i8 @main.readLargeValue(ptr %param, ptr undef)
+  br label %rundefers.loophead
+
+rundefers.default:                                ; preds = %rundefers.loop
+  unreachable
+
+rundefers.end:                                    ; preds = %rundefers.loophead
+  br label %rundefers.after
+
+recover:                                          ; No predecessors!
+  ret void
+}
+
+; Function Attrs: nounwind
+define hidden void @main.goLargeValue(ptr readonly dereferenceable_or_null(1025) %value, ptr %context) unnamed_addr #1 {
+entry:
+  %stackalloc = alloca i8, align 1
+  %go.param = call align 1 dereferenceable(1025) ptr @runtime.alloc(i32 1025, ptr nonnull inttoptr (i32 3 to ptr), ptr undef) #9
+  call void @runtime.trackPointer(ptr nonnull %go.param, ptr nonnull %stackalloc, ptr undef) #9
+  call void @llvm.memcpy.p0.p0.i32(ptr noundef nonnull align 1 dereferenceable(1025) %go.param, ptr noundef nonnull align 1 dereferenceable(1025) %value, i32 1025, i1 false)
+  call void @"internal/task.start"(i32 ptrtoint (ptr @"main.readLargeValue$gowrapper" to i32), ptr nonnull %go.param, i32 65536, ptr undef) #9
+  ret void
+}
+
+declare void @runtime.deadlock(ptr) #0
+
+; Function Attrs: nounwind
+define linkonce_odr void @"main.readLargeValue$gowrapper"(ptr %0) unnamed_addr #6 {
+entry:
+  %1 = call i8 @main.readLargeValue(ptr %0, ptr undef)
+  call void @runtime.deadlock(ptr undef) #9
+  unreachable
+}
+
+declare void @"internal/task.start"(i32, ptr, i32, ptr) #0
+
+; Function Attrs: nounwind
+define hidden void @main.makeLargeResults(ptr dereferenceable_or_null(1026) %return, i8 %value, ptr %context) unnamed_addr #1 {
+entry:
+  %stackalloc = alloca i8, align 1
+  %call.result = call align 1 dereferenceable(1025) ptr @runtime.alloc(i32 1025, ptr nonnull inttoptr (i32 3 to ptr), ptr undef) #9
+  call void @runtime.trackPointer(ptr nonnull %call.result, ptr nonnull %stackalloc, ptr undef) #9
+  call void @main.makeLargeValue(ptr nonnull %call.result, i8 %value, ptr undef)
+  call void @llvm.memcpy.p0.p0.i32(ptr noundef nonnull align 1 dereferenceable(1025) %return, ptr noundef nonnull align 1 dereferenceable(1025) %call.result, i32 1025, i1 false)
+  %0 = getelementptr inbounds nuw i8, ptr %return, i32 1025
+  store i8 %value, ptr %0, align 1
+  ret void
+}
+
+; Function Attrs: nounwind
+define hidden void @main.makeTwoLargeResults(ptr dereferenceable_or_null(2050) %return, i8 %value, ptr %context) unnamed_addr #1 {
+entry:
+  %stackalloc = alloca i8, align 1
+  %call.result = call align 1 dereferenceable(1025) ptr @runtime.alloc(i32 1025, ptr nonnull inttoptr (i32 3 to ptr), ptr undef) #9
+  call void @runtime.trackPointer(ptr nonnull %call.result, ptr nonnull %stackalloc, ptr undef) #9
+  call void @main.makeLargeValue(ptr nonnull %call.result, i8 %value, ptr undef)
+  %0 = add i8 %value, 1
+  %call.result1 = call align 1 dereferenceable(1025) ptr @runtime.alloc(i32 1025, ptr nonnull inttoptr (i32 3 to ptr), ptr undef) #9
+  call void @runtime.trackPointer(ptr nonnull %call.result1, ptr nonnull %stackalloc, ptr undef) #9
+  call void @main.makeLargeValue(ptr nonnull %call.result1, i8 %0, ptr undef)
+  call void @llvm.memcpy.p0.p0.i32(ptr noundef nonnull align 1 dereferenceable(1025) %return, ptr noundef nonnull align 1 dereferenceable(1025) %call.result, i32 1025, i1 false)
+  %1 = getelementptr inbounds nuw i8, ptr %return, i32 1025
+  call void @llvm.memcpy.p0.p0.i32(ptr noundef nonnull align 1 dereferenceable(1025) %1, ptr noundef nonnull align 1 dereferenceable(1025) %call.result1, i32 1025, i1 false)
+  ret void
+}
+
+; Function Attrs: nounwind
+define hidden void @main.makeMixedLargeResults(ptr dereferenceable_or_null(2051) %return, i8 %value, ptr %context) unnamed_addr #1 {
+entry:
+  %stackalloc = alloca i8, align 1
+  %call.result = call align 1 dereferenceable(1025) ptr @runtime.alloc(i32 1025, ptr nonnull inttoptr (i32 3 to ptr), ptr undef) #9
+  call void @runtime.trackPointer(ptr nonnull %call.result, ptr nonnull %stackalloc, ptr undef) #9
+  call void @main.makeLargeValue(ptr nonnull %call.result, i8 %value, ptr undef)
+  %0 = add i8 %value, 1
+  %1 = add i8 %value, 2
+  %call.result1 = call align 1 dereferenceable(1025) ptr @runtime.alloc(i32 1025, ptr nonnull inttoptr (i32 3 to ptr), ptr undef) #9
+  call void @runtime.trackPointer(ptr nonnull %call.result1, ptr nonnull %stackalloc, ptr undef) #9
+  call void @main.makeLargeValue(ptr nonnull %call.result1, i8 %1, ptr undef)
+  call void @llvm.memcpy.p0.p0.i32(ptr noundef nonnull align 1 dereferenceable(1025) %return, ptr noundef nonnull align 1 dereferenceable(1025) %call.result, i32 1025, i1 false)
+  %2 = getelementptr inbounds nuw i8, ptr %return, i32 1025
+  store i8 %0, ptr %2, align 1
+  %3 = getelementptr inbounds nuw i8, ptr %return, i32 1026
+  call void @llvm.memcpy.p0.p0.i32(ptr noundef nonnull align 1 dereferenceable(1025) %3, ptr noundef nonnull align 1 dereferenceable(1025) %call.result1, i32 1025, i1 false)
+  ret void
+}
+
+; Function Attrs: nounwind
+define hidden void @main.chooseLargeValue(ptr dereferenceable_or_null(1025) %return, i1 %flag, ptr %context) unnamed_addr #1 {
+entry:
+  %stackalloc = alloca i8, align 1
+  %call.result = call align 1 dereferenceable(1025) ptr @runtime.alloc(i32 1025, ptr nonnull inttoptr (i32 3 to ptr), ptr undef) #9
+  call void @runtime.trackPointer(ptr nonnull %call.result, ptr nonnull %stackalloc, ptr undef) #9
+  call void @main.makeLargeValue(ptr nonnull %call.result, i8 1, ptr undef)
+  br i1 %flag, label %if.then, label %if.done
+
+if.then:                                          ; preds = %entry
+  %call.result1 = call align 1 dereferenceable(1025) ptr @runtime.alloc(i32 1025, ptr nonnull inttoptr (i32 3 to ptr), ptr undef) #9
+  call void @runtime.trackPointer(ptr nonnull %call.result1, ptr nonnull %stackalloc, ptr undef) #9
+  call void @main.makeLargeValue(ptr nonnull %call.result1, i8 42, ptr undef)
+  br label %if.done
+
+if.done:                                          ; preds = %if.then, %entry
+  %0 = phi ptr [ %call.result, %entry ], [ %call.result1, %if.then ]
+  call void @llvm.memcpy.p0.p0.i32(ptr noundef nonnull align 1 dereferenceable(1025) %return, ptr noundef nonnull align 1 dereferenceable(1025) %0, i32 1025, i1 false)
+  ret void
+}
+
+; Function Attrs: nounwind
+define hidden void @main.makePointerLargeValue(ptr dereferenceable_or_null(1032) %return, ptr dereferenceable_or_null(1) %value, ptr %context) unnamed_addr #1 {
+entry:
+  %stackalloc = alloca i8, align 1
+  %complit = call align 4 dereferenceable(1032) ptr @runtime.alloc(i32 1032, ptr nonnull @"runtime/gc.layout:258-000000000000000000000000000000000000000000000000000000000000000002", ptr undef) #9
+  call void @runtime.trackPointer(ptr nonnull %complit, ptr nonnull %stackalloc, ptr undef) #9
+  br i1 false, label %store.throw, label %store.next
+
+store.next:                                       ; preds = %entry
+  %0 = getelementptr inbounds nuw i8, ptr %complit, i32 1028
+  store ptr %value, ptr %0, align 4
+  %1 = call align 4 dereferenceable(1032) ptr @runtime.alloc(i32 1032, ptr nonnull @"runtime/gc.layout:258-000000000000000000000000000000000000000000000000000000000000000002", ptr undef) #9
+  call void @runtime.trackPointer(ptr nonnull %1, ptr nonnull %stackalloc, ptr undef) #9
+  call void @llvm.memcpy.p0.p0.i32(ptr noundef nonnull align 4 dereferenceable(1032) %1, ptr noundef nonnull align 4 dereferenceable(1032) %complit, i32 1032, i1 false)
+  call void @llvm.memcpy.p0.p0.i32(ptr noundef nonnull align 1 dereferenceable(1032) %return, ptr noundef nonnull align 4 dereferenceable(1032) %1, i32 1032, i1 false)
+  ret void
+
+store.throw:                                      ; preds = %entry
+  unreachable
+}
+
+; Function Attrs: nounwind
+define hidden i8 @main.assertLargeValue(ptr %value.typecode, ptr %value.value, ptr %context) unnamed_addr #1 {
+entry:
+  %stackalloc = alloca i8, align 1
+  %large = call align 1 dereferenceable(1025) ptr @runtime.alloc(i32 1025, ptr nonnull inttoptr (i32 3 to ptr), ptr undef) #9
+  call void @runtime.trackPointer(ptr nonnull %large, ptr nonnull %stackalloc, ptr undef) #9
+  %typecode = call i1 @runtime.typeAssert(ptr %value.typecode, ptr nonnull @"reflect/types.typeid:named:main.largeValue", ptr undef) #9
+  %typeassert.result = call align 1 dereferenceable(1026) ptr @runtime.alloc(i32 1026, ptr nonnull inttoptr (i32 3 to ptr), ptr undef) #9
+  call void @runtime.trackPointer(ptr nonnull %typeassert.result, ptr nonnull %stackalloc, ptr undef) #9
+  call void @llvm.memset.p0.i32(ptr noundef nonnull align 1 dereferenceable(1026) %typeassert.result, i8 0, i32 1026, i1 false)
+  br i1 %typecode, label %typeassert.ok, label %typeassert.next
+
+typeassert.next:                                  ; preds = %typeassert.ok, %entry
+  %0 = getelementptr inbounds nuw i8, ptr %typeassert.result, i32 1025
+  store i1 %typecode, ptr %0, align 1
+  %t2 = call align 1 dereferenceable(1025) ptr @runtime.alloc(i32 1025, ptr nonnull inttoptr (i32 3 to ptr), ptr undef) #9
+  call void @runtime.trackPointer(ptr nonnull %t2, ptr nonnull %stackalloc, ptr undef) #9
+  call void @llvm.memcpy.p0.p0.i32(ptr noundef nonnull align 1 dereferenceable(1025) %t2, ptr noundef nonnull align 1 dereferenceable(1025) %typeassert.result, i32 1025, i1 false)
+  call void @llvm.memcpy.p0.p0.i32(ptr noundef nonnull align 1 dereferenceable(1025) %large, ptr noundef nonnull align 1 dereferenceable(1025) %t2, i32 1025, i1 false)
+  br i1 %typecode, label %if.done, label %if.then
+
+typeassert.ok:                                    ; preds = %entry
+  call void @llvm.memcpy.p0.p0.i32(ptr noundef nonnull align 1 dereferenceable(1025) %typeassert.result, ptr noundef nonnull align 1 dereferenceable(1025) %value.value, i32 1025, i1 false)
+  br label %typeassert.next
+
+if.done:                                          ; preds = %typeassert.next
+  %1 = getelementptr inbounds nuw i8, ptr %large, i32 1024
+  %2 = load i8, ptr %1, align 1
+  ret i8 %2
+
+if.then:                                          ; preds = %typeassert.next
+  ret i8 0
+}
+
+declare i1 @runtime.typeAssert(ptr, ptr dereferenceable_or_null(1), ptr) #0
+
+; Function Attrs: nocallback nofree nounwind willreturn memory(argmem: write)
+declare void @llvm.memset.p0.i32(ptr writeonly captures(none), i8, i32, i1 immarg) #7
+
+; Function Attrs: nounwind
+define hidden i8 @main.useLargeMap(ptr readonly dereferenceable_or_null(1025) %key, ptr readonly dereferenceable_or_null(1025) %value, ptr %context) unnamed_addr #1 {
+entry:
+  %stackalloc = alloca i8, align 1
+  %0 = call ptr @runtime.hashmapMakeGeneric(i32 1025, i32 1025, i32 1, ptr null, ptr nonnull @runtime.hash32, ptr null, ptr nonnull @runtime.memequal, ptr undef) #9
+  call void @runtime.trackPointer(ptr %0, ptr nonnull %stackalloc, ptr undef) #9
+  call void @runtime.hashmapBinarySet(ptr %0, ptr %key, ptr %value, ptr undef) #9
+  %result = call align 1 dereferenceable(1025) ptr @runtime.alloc(i32 1025, ptr nonnull inttoptr (i32 3 to ptr), ptr undef) #9
+  call void @runtime.trackPointer(ptr nonnull %result, ptr nonnull %stackalloc, ptr undef) #9
+  %hashmap.result = call align 1 dereferenceable(1026) ptr @runtime.alloc(i32 1026, ptr nonnull inttoptr (i32 3 to ptr), ptr undef) #9
+  call void @runtime.trackPointer(ptr nonnull %hashmap.result, ptr nonnull %stackalloc, ptr undef) #9
+  %1 = call i1 @runtime.hashmapBinaryGet(ptr %0, ptr %key, ptr nonnull %hashmap.result, i32 1025, ptr undef) #9
+  %2 = getelementptr inbounds nuw i8, ptr %hashmap.result, i32 1025
+  store i1 %1, ptr %2, align 1
+  %t3 = call align 1 dereferenceable(1025) ptr @runtime.alloc(i32 1025, ptr nonnull inttoptr (i32 3 to ptr), ptr undef) #9
+  call void @runtime.trackPointer(ptr nonnull %t3, ptr nonnull %stackalloc, ptr undef) #9
+  call void @llvm.memcpy.p0.p0.i32(ptr noundef nonnull align 1 dereferenceable(1025) %t3, ptr noundef nonnull align 1 dereferenceable(1025) %hashmap.result, i32 1025, i1 false)
+  call void @llvm.memcpy.p0.p0.i32(ptr noundef nonnull align 1 dereferenceable(1025) %result, ptr noundef nonnull align 1 dereferenceable(1025) %t3, i32 1025, i1 false)
+  %3 = getelementptr inbounds nuw i8, ptr %hashmap.result, i32 1025
+  %t4 = load i1, ptr %3, align 1
+  br i1 %t4, label %if.done, label %if.then
+
+if.done:                                          ; preds = %entry
+  %4 = getelementptr inbounds nuw i8, ptr %result, i32 1024
+  %5 = load i8, ptr %4, align 1
+  ret i8 %5
+
+if.then:                                          ; preds = %entry
+  ret i8 0
+}
+
+declare i32 @runtime.hash32(ptr, i32, i32, ptr) #0
+
+declare i1 @runtime.memequal(ptr, ptr, i32, ptr) #0
+
+declare ptr @runtime.hashmapMakeGeneric(i32, i32, i32, ptr, ptr, ptr, ptr, ptr) #0
+
+declare void @runtime.hashmapBinarySet(ptr dereferenceable_or_null(48), ptr, ptr, ptr) #0
+
+declare i1 @runtime.hashmapBinaryGet(ptr dereferenceable_or_null(48), ptr, ptr, i32, ptr) #0
+
+; Function Attrs: nounwind
+define hidden i8 @main.useLargeChannel(ptr dereferenceable_or_null(36) %ch, ptr readonly dereferenceable_or_null(1025) %value, ptr %context) unnamed_addr #1 {
+entry:
+  %chan.op1 = alloca %runtime.channelOp, align 8
+  %chan.op = alloca %runtime.channelOp, align 8
+  %stackalloc = alloca i8, align 1
+  call void @llvm.lifetime.start.p0(ptr nonnull %chan.op)
+  call void @runtime.chanSend(ptr %ch, ptr %value, ptr nonnull %chan.op, ptr undef) #9
+  call void @llvm.lifetime.end.p0(ptr nonnull %chan.op)
+  %result = call align 1 dereferenceable(1025) ptr @runtime.alloc(i32 1025, ptr nonnull inttoptr (i32 3 to ptr), ptr undef) #9
+  call void @runtime.trackPointer(ptr nonnull %result, ptr nonnull %stackalloc, ptr undef) #9
+  %chan.result = call align 1 dereferenceable(1026) ptr @runtime.alloc(i32 1026, ptr nonnull inttoptr (i32 3 to ptr), ptr undef) #9
+  call void @runtime.trackPointer(ptr nonnull %chan.result, ptr nonnull %stackalloc, ptr undef) #9
+  call void @llvm.lifetime.start.p0(ptr nonnull %chan.op1)
+  %0 = call i1 @runtime.chanRecv(ptr %ch, ptr nonnull %chan.result, ptr nonnull %chan.op1, ptr undef) #9
+  %1 = getelementptr inbounds nuw i8, ptr %chan.result, i32 1025
+  store i1 %0, ptr %1, align 1
+  call void @llvm.lifetime.end.p0(ptr nonnull %chan.op1)
+  %t2 = call align 1 dereferenceable(1025) ptr @runtime.alloc(i32 1025, ptr nonnull inttoptr (i32 3 to ptr), ptr undef) #9
+  call void @runtime.trackPointer(ptr nonnull %t2, ptr nonnull %stackalloc, ptr undef) #9
+  call void @llvm.memcpy.p0.p0.i32(ptr noundef nonnull align 1 dereferenceable(1025) %t2, ptr noundef nonnull align 1 dereferenceable(1025) %chan.result, i32 1025, i1 false)
+  call void @llvm.memcpy.p0.p0.i32(ptr noundef nonnull align 1 dereferenceable(1025) %result, ptr noundef nonnull align 1 dereferenceable(1025) %t2, i32 1025, i1 false)
+  %2 = getelementptr inbounds nuw i8, ptr %chan.result, i32 1025
+  %t3 = load i1, ptr %2, align 1
+  br i1 %t3, label %if.done, label %if.then
+
+if.done:                                          ; preds = %entry
+  %3 = getelementptr inbounds nuw i8, ptr %result, i32 1024
+  %4 = load i8, ptr %3, align 1
+  ret i8 %4
+
+if.then:                                          ; preds = %entry
+  ret i8 0
+}
+
+; Function Attrs: nocallback nofree nosync nounwind willreturn memory(argmem: readwrite)
+declare void @llvm.lifetime.start.p0(ptr captures(none)) #8
+
+declare void @runtime.chanSend(ptr dereferenceable_or_null(36), ptr, ptr dereferenceable_or_null(16), ptr) #0
+
+; Function Attrs: nocallback nofree nosync nounwind willreturn memory(argmem: readwrite)
+declare void @llvm.lifetime.end.p0(ptr captures(none)) #8
+
+declare i1 @runtime.chanRecv(ptr dereferenceable_or_null(36), ptr, ptr dereferenceable_or_null(16), ptr) #0
+
+; Function Attrs: nounwind
+define hidden i8 @main.selectLargeChannel(ptr dereferenceable_or_null(36) %ch, ptr readonly dereferenceable_or_null(1025) %value, ptr %context) unnamed_addr #1 {
+entry:
+  %select.block.alloca = alloca [2 x %runtime.channelOp], align 8
+  %select.states.alloca = alloca [2 x %runtime.chanSelectState], align 8
+  %select.recvbuf.alloca = alloca [1025 x i8], align 1
+  %stackalloc = alloca i8, align 1
+  call void @llvm.lifetime.start.p0(ptr nonnull %select.recvbuf.alloca)
+  call void @llvm.lifetime.start.p0(ptr nonnull %select.states.alloca)
+  store ptr %ch, ptr %select.states.alloca, align 4
+  %select.states.alloca.repack3 = getelementptr inbounds nuw i8, ptr %select.states.alloca, i32 4
+  store ptr %value, ptr %select.states.alloca.repack3, align 4
+  %0 = getelementptr inbounds nuw i8, ptr %select.states.alloca, i32 8
+  store ptr %ch, ptr %0, align 4
+  %.repack5 = getelementptr inbounds nuw i8, ptr %select.states.alloca, i32 12
+  store ptr null, ptr %.repack5, align 4
+  call void @llvm.lifetime.start.p0(ptr nonnull %select.block.alloca)
+  %select.result = call { i32, i1 } @runtime.chanSelect(ptr nonnull %select.recvbuf.alloca, ptr nonnull %select.states.alloca, i32 2, i32 2, ptr nonnull %select.block.alloca, i32 2, i32 2, ptr undef) #9
+  call void @llvm.lifetime.end.p0(ptr nonnull %select.block.alloca)
+  call void @llvm.lifetime.end.p0(ptr nonnull %select.states.alloca)
+  call void @runtime.trackPointer(ptr nonnull %select.recvbuf.alloca, ptr nonnull %stackalloc, ptr undef) #9
+  %1 = extractvalue { i32, i1 } %select.result, 0
+  %2 = icmp eq i32 %1, 0
+  br i1 %2, label %select.body, label %select.next
+
+select.body:                                      ; preds = %entry
+  ret i8 0
+
+select.next:                                      ; preds = %entry
+  %3 = icmp eq i32 %1, 1
+  br i1 %3, label %select.body1, label %select.next2
+
+select.body1:                                     ; preds = %select.next
+  %result = call align 1 dereferenceable(1025) ptr @runtime.alloc(i32 1025, ptr nonnull inttoptr (i32 3 to ptr), ptr undef) #9
+  call void @runtime.trackPointer(ptr nonnull %result, ptr nonnull %stackalloc, ptr undef) #9
+  %select.received = call align 1 dereferenceable(1025) ptr @runtime.alloc(i32 1025, ptr nonnull inttoptr (i32 3 to ptr), ptr undef) #9
+  call void @runtime.trackPointer(ptr nonnull %select.received, ptr nonnull %stackalloc, ptr undef) #9
+  call void @llvm.memcpy.p0.p0.i32(ptr noundef nonnull align 1 dereferenceable(1025) %select.received, ptr noundef nonnull align 1 dereferenceable(1025) %select.recvbuf.alloca, i32 1025, i1 false)
+  call void @llvm.memcpy.p0.p0.i32(ptr noundef nonnull align 1 dereferenceable(1025) %result, ptr noundef nonnull align 1 dereferenceable(1025) %select.received, i32 1025, i1 false)
+  %4 = getelementptr inbounds nuw i8, ptr %result, i32 1024
+  %5 = load i8, ptr %4, align 1
+  ret i8 %5
+
+select.next2:                                     ; preds = %select.next
+  call void @runtime.trackPointer(ptr nonnull @"reflect/types.type:basic:string", ptr nonnull %stackalloc, ptr undef) #9
+  call void @runtime.trackPointer(ptr nonnull @"main$pack", ptr nonnull %stackalloc, ptr undef) #9
+  call void @runtime._panic(ptr nonnull @"reflect/types.type:basic:string", ptr nonnull @"main$pack", ptr undef) #9
+  unreachable
+}
+
+declare { i32, i1 } @runtime.chanSelect(ptr, ptr, i32, i32, ptr, i32, i32, ptr) #0
+
+declare void @runtime._panic(ptr, ptr, ptr) #0
+
+attributes #0 = { "target-features"="+bulk-memory,+bulk-memory-opt,+call-indirect-overlong,+mutable-globals,+nontrapping-fptoint,+sign-ext,-multivalue,-reference-types" }
+attributes #1 = { nounwind "target-features"="+bulk-memory,+bulk-memory-opt,+call-indirect-overlong,+mutable-globals,+nontrapping-fptoint,+sign-ext,-multivalue,-reference-types" }
+attributes #2 = { nocallback nofree nounwind willreturn memory(argmem: readwrite) }
+attributes #3 = { allockind("alloc,zeroed") allocsize(0) "alloc-family"="runtime.alloc" "target-features"="+bulk-memory,+bulk-memory-opt,+call-indirect-overlong,+mutable-globals,+nontrapping-fptoint,+sign-ext,-multivalue,-reference-types" }
+attributes #4 = { "target-features"="+bulk-memory,+bulk-memory-opt,+call-indirect-overlong,+mutable-globals,+nontrapping-fptoint,+sign-ext,-multivalue,-reference-types" "tinygo-indirect-result"="true" "tinygo-invoke"="main.$methods.makeLargeValue:func:{}{named:main.largeValue}" "tinygo-methods"="main.$methods.makeLargeValue:func:{}{named:main.largeValue}; main.$methods.readLargeValue:func:{named:main.largeValue}{basic:uint8}" }
+attributes #5 = { "target-features"="+bulk-memory,+bulk-memory-opt,+call-indirect-overlong,+mutable-globals,+nontrapping-fptoint,+sign-ext,-multivalue,-reference-types" "tinygo-invoke"="main.$methods.readLargeValue:func:{named:main.largeValue}{basic:uint8}" "tinygo-methods"="main.$methods.makeLargeValue:func:{}{named:main.largeValue}; main.$methods.readLargeValue:func:{named:main.largeValue}{basic:uint8}" }
+attributes #6 = { nounwind "target-features"="+bulk-memory,+bulk-memory-opt,+call-indirect-overlong,+mutable-globals,+nontrapping-fptoint,+sign-ext,-multivalue,-reference-types" "tinygo-gowrapper"="main.readLargeValue" }
+attributes #7 = { nocallback nofree nounwind willreturn memory(argmem: write) }
+attributes #8 = { nocallback nofree nosync nounwind willreturn memory(argmem: readwrite) }
+attributes #9 = { nounwind }
diff --git a/transform/interface-lowering.go b/transform/interface-lowering.go
index 6e5af1559d..9c1adf7247 100644
--- a/transform/interface-lowering.go
+++ b/transform/interface-lowering.go
@@ -517,6 +517,10 @@ func (p *lowerInterfacesPass) defineInterfaceMethodFunc(fn llvm.Value, itf *inte
 	context := fn.LastParam()
 	actualType := llvm.PrevParam(context)
 	returnType := fn.GlobalValueType().ReturnType()
+	resultOffset := 0
+	if fn.GetStringAttributeAtIndex(-1, "tinygo-indirect-result").GetStringValue() == "true" {
+		resultOffset = 1
+	}
 	context.SetName("context")
 	actualType.SetName("actualType")
 	fn.SetLinkage(llvm.InternalLinkage)
@@ -526,9 +530,9 @@ func (p *lowerInterfacesPass) defineInterfaceMethodFunc(fn llvm.Value, itf *inte
 	// Collect the params that will be passed to the functions to call.
 	// These params exclude the receiver (which may actually consist of multiple
 	// parts).
-	params := make([]llvm.Value, fn.ParamsCount()-3)
+	params := make([]llvm.Value, fn.ParamsCount()-3-resultOffset)
 	for i := range params {
-		params[i] = fn.Param(i + 1)
+		params[i] = fn.Param(i + 1 + resultOffset)
 	}
 	params = append(params,
 		llvm.Undef(p.ptrType),
@@ -570,14 +574,20 @@ func (p *lowerInterfacesPass) defineInterfaceMethodFunc(fn llvm.Value, itf *inte
 		function := typ.getMethod(signature).function
 
 		p.builder.SetInsertPointAtEnd(bb)
-		receiver := fn.FirstParam()
+		receiver := fn.Param(resultOffset)
 
-		paramTypes := []llvm.Type{receiver.Type()}
-		for _, param := range params {
-			paramTypes = append(paramTypes, param.Type())
+		callParams := make([]llvm.Value, 0, len(params)+2+resultOffset)
+		if resultOffset != 0 {
+			callParams = append(callParams, fn.FirstParam())
+		}
+		callParams = append(callParams, receiver)
+		callParams = append(callParams, params...)
+		paramTypes := make([]llvm.Type, len(callParams))
+		for i, param := range callParams {
+			paramTypes[i] = param.Type()
 		}
 		functionType := llvm.FunctionType(returnType, paramTypes, false)
-		retval := p.builder.CreateCall(functionType, function, append([]llvm.Value{receiver}, params...), "")
+		retval := p.builder.CreateCall(functionType, function, callParams, "")
 		if retval.Type().TypeKind() == llvm.VoidTypeKind {
 			p.builder.CreateRetVoid()
 		} else {