wasm: fix C realloc and optimize it a bit

compiler/map.go

@@ -250,6 +250,9 @@ func (b *builder) createMapIteratorNext(rangeVal ssa.Value, llvmRangeVal, it llv
 func hashmapIsBinaryKey(keyType types.Type) bool {
 	switch keyType := keyType.(type) {
 	case *types.Basic:
+		if keyType.Kind() == types.UnsafePointer {
+			return true
+		}
 		return keyType.Info()&(types.IsBoolean|types.IsInteger) != 0
 	case *types.Pointer:
 		return true

src/runtime/arch_tinygowasm_malloc.go

@@ -8,16 +8,17 @@ import "unsafe"
 // code linked from other languages can allocate memory without colliding with
 // our GC allocations.
 
-var allocs = make(map[uintptr][]byte)
+// Map of allocations, where the key is the allocated pointer and the value is
+// the size of the allocation.
+var allocs = make(map[unsafe.Pointer]uintptr)
 
 //export malloc
 func libc_malloc(size uintptr) unsafe.Pointer {
 	if size == 0 {
 		return nil
 	}
-	buf := make([]byte, size)
-	ptr := unsafe.Pointer(&buf[0])
-	allocs[uintptr(ptr)] = buf
+	ptr := alloc(size, nil)
+	allocs[ptr] = size
 	return ptr
 }
 
@@ -26,8 +27,8 @@ func libc_free(ptr unsafe.Pointer) {
 	if ptr == nil {
 		return
 	}
-	if _, ok := allocs[uintptr(ptr)]; ok {
-		delete(allocs, uintptr(ptr))
+	if _, ok := allocs[ptr]; ok {
+		delete(allocs, ptr)
 	} else {
 		panic("free: invalid pointer")
 	}
@@ -48,18 +49,20 @@ func libc_realloc(oldPtr unsafe.Pointer, size uintptr) unsafe.Pointer {
 
 	// It's hard to optimize this to expand the current buffer with our GC, but
 	// it is theoretically possible. For now, just always allocate fresh.
-	buf := make([]byte, size)
+	// TODO: we could skip this if the new allocation is smaller than the old.
+	ptr := alloc(size, nil)
 
 	if oldPtr != nil {
-		if oldBuf, ok := allocs[uintptr(oldPtr)]; ok {
-			copy(buf, oldBuf)
-			delete(allocs, uintptr(oldPtr))
+		if oldSize, ok := allocs[oldPtr]; ok {
+			oldBuf := unsafe.Slice((*byte)(oldPtr), oldSize)
+			newBuf := unsafe.Slice((*byte)(ptr), size)
+			copy(newBuf, oldBuf)
+			delete(allocs, oldPtr)
 		} else {
 			panic("realloc: invalid pointer")
 		}
 	}
 
-	ptr := unsafe.Pointer(&buf[0])
-	allocs[uintptr(ptr)] = buf
+	allocs[ptr] = size
 	return ptr
 }