[VPlan] Use VP intrinsics for trapping divisors with EVL tail folding #154076
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If a widened div or rem has a divisor that's not known to be non-zero, the potentially trapping lanes of the divisor are masked with ones. If the target is using EVL tail folding, we can instead mask those lanes with VP intrinsics. We can also further optimise this to remove the mask and instead use the EVL argument if the mask is exactly the header mask. This removes unnecessary vmv.v.is on RISC-V, and fixes llvm#129538
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@llvm/pr-subscribers-vectorizers @llvm/pr-subscribers-llvm-transforms Author: Luke Lau (lukel97) ChangesIf a widened div or rem has a divisor that's not known to be non-zero, the potentially trapping lanes of the divisor are masked with ones. If the target is using EVL tail folding, we can instead mask those lanes with VP intrinsics. We can also further optimise this to remove the mask and instead use the EVL argument if the mask is exactly the header mask. This removes unnecessary vmv.v.is on RISC-V, and fixes #129538 Full diff: https://github.com/llvm/llvm-project/pull/154076.diff 5 Files Affected:
diff --git a/llvm/lib/Transforms/Vectorize/LoopVectorize.cpp b/llvm/lib/Transforms/Vectorize/LoopVectorize.cpp
index 675a230bd2c94..310e64eb7c615 100644
--- a/llvm/lib/Transforms/Vectorize/LoopVectorize.cpp
+++ b/llvm/lib/Transforms/Vectorize/LoopVectorize.cpp
@@ -7932,8 +7932,8 @@ bool VPRecipeBuilder::shouldWiden(Instruction *I, VFRange &Range) const {
Range);
}
-VPWidenRecipe *VPRecipeBuilder::tryToWiden(Instruction *I,
- ArrayRef<VPValue *> Operands) {
+VPRecipeWithIRFlags *VPRecipeBuilder::tryToWiden(Instruction *I,
+ ArrayRef<VPValue *> Operands) {
switch (I->getOpcode()) {
default:
return nullptr;
@@ -7941,11 +7941,23 @@ VPWidenRecipe *VPRecipeBuilder::tryToWiden(Instruction *I,
case Instruction::UDiv:
case Instruction::SRem:
case Instruction::URem: {
- // If not provably safe, use a select to form a safe divisor before widening the
- // div/rem operation itself. Otherwise fall through to general handling below.
+ // If not provably safe use a VP intrinsic to mask off trapping lanes if
+ // supported, or use a select to form a safe divisor before widening the
+ // div/rem operation itself.
+ // Otherwise fall through to general handling below.
if (CM.isPredicatedInst(I)) {
SmallVector<VPValue *> Ops(Operands);
VPValue *Mask = getBlockInMask(Builder.getInsertBlock());
+
+ if (CM.foldTailWithEVL()) {
+ Ops.push_back(Mask);
+ Ops.push_back(Plan.getOrAddLiveIn(ConstantInt::getAllOnesValue(
+ IntegerType::getInt32Ty(I->getContext()))));
+ return new VPWidenIntrinsicRecipe(
+ VPIntrinsic::getForOpcode(I->getOpcode()), Ops, I->getType(),
+ I->getDebugLoc());
+ }
+
VPValue *One =
Plan.getOrAddLiveIn(ConstantInt::get(I->getType(), 1u, false));
auto *SafeRHS = Builder.createSelect(Mask, Ops[1], One, I->getDebugLoc());
diff --git a/llvm/lib/Transforms/Vectorize/VPRecipeBuilder.h b/llvm/lib/Transforms/Vectorize/VPRecipeBuilder.h
index 41878e3c648e3..6696caefa3a04 100644
--- a/llvm/lib/Transforms/Vectorize/VPRecipeBuilder.h
+++ b/llvm/lib/Transforms/Vectorize/VPRecipeBuilder.h
@@ -121,7 +121,7 @@ class VPRecipeBuilder {
/// Check if \p I has an opcode that can be widened and return a VPWidenRecipe
/// if it can. The function should only be called if the cost-model indicates
/// that widening should be performed.
- VPWidenRecipe *tryToWiden(Instruction *I, ArrayRef<VPValue *> Operands);
+ VPRecipeWithIRFlags *tryToWiden(Instruction *I, ArrayRef<VPValue *> Operands);
/// Makes Histogram count operations safe for vectorization, by emitting a
/// llvm.experimental.vector.histogram.add intrinsic in place of the
diff --git a/llvm/lib/Transforms/Vectorize/VPlanTransforms.cpp b/llvm/lib/Transforms/Vectorize/VPlanTransforms.cpp
index de0c1e4d177bb..5300bdccadbb3 100644
--- a/llvm/lib/Transforms/Vectorize/VPlanTransforms.cpp
+++ b/llvm/lib/Transforms/Vectorize/VPlanTransforms.cpp
@@ -2174,6 +2174,29 @@ static VPRecipeBase *optimizeMaskToEVL(VPValue *HeaderMask,
Intrinsic::vp_merge, {&AllOneMask, LHS, RHS, &EVL},
TypeInfo.inferScalarType(LHS), VPI->getDebugLoc());
})
+ .Case<VPWidenIntrinsicRecipe>(
+ [&](VPWidenIntrinsicRecipe *VPI) -> VPRecipeBase * {
+ switch (VPI->getVectorIntrinsicID()) {
+ case Intrinsic::vp_udiv:
+ case Intrinsic::vp_sdiv:
+ case Intrinsic::vp_urem:
+ case Intrinsic::vp_srem:
+ break;
+ default:
+ return nullptr;
+ }
+ if (!match(VPI->getOperand(3), m_AllOnes()))
+ return nullptr;
+ VPValue *NewMask = GetNewMask(VPI->getOperand(2));
+ if (NewMask == HeaderMask)
+ return nullptr;
+ if (!NewMask)
+ NewMask = &AllOneMask;
+ return new VPWidenIntrinsicRecipe(
+ VPI->getVectorIntrinsicID(),
+ {VPI->getOperand(0), VPI->getOperand(1), NewMask, &EVL},
+ VPI->getResultType(), VPI->getDebugLoc());
+ })
.Default([&](VPRecipeBase *R) { return nullptr; });
}
diff --git a/llvm/test/Transforms/LoopVectorize/RISCV/divrem.ll b/llvm/test/Transforms/LoopVectorize/RISCV/divrem.ll
index 3af328fb6568e..e7900cc086a40 100644
--- a/llvm/test/Transforms/LoopVectorize/RISCV/divrem.ll
+++ b/llvm/test/Transforms/LoopVectorize/RISCV/divrem.ll
@@ -371,8 +371,7 @@ define void @predicated_udiv(ptr noalias nocapture %a, i64 %v, i64 %n) {
; CHECK-NEXT: [[TMP8:%.*]] = getelementptr inbounds i64, ptr [[A:%.*]], i64 [[INDEX]]
; CHECK-NEXT: [[WIDE_LOAD:%.*]] = call <vscale x 2 x i64> @llvm.vp.load.nxv2i64.p0(ptr align 8 [[TMP8]], <vscale x 2 x i1> splat (i1 true), i32 [[TMP12]])
; CHECK-NEXT: [[TMP16:%.*]] = select <vscale x 2 x i1> [[TMP15]], <vscale x 2 x i1> [[TMP6]], <vscale x 2 x i1> zeroinitializer
-; CHECK-NEXT: [[TMP10:%.*]] = select <vscale x 2 x i1> [[TMP16]], <vscale x 2 x i64> [[BROADCAST_SPLAT]], <vscale x 2 x i64> splat (i64 1)
-; CHECK-NEXT: [[TMP11:%.*]] = udiv <vscale x 2 x i64> [[WIDE_LOAD]], [[TMP10]]
+; CHECK-NEXT: [[TMP11:%.*]] = call <vscale x 2 x i64> @llvm.vp.udiv.nxv2i64(<vscale x 2 x i64> [[WIDE_LOAD]], <vscale x 2 x i64> [[BROADCAST_SPLAT]], <vscale x 2 x i1> [[TMP6]], i32 [[TMP12]])
; CHECK-NEXT: [[PREDPHI:%.*]] = select <vscale x 2 x i1> [[TMP16]], <vscale x 2 x i64> [[TMP11]], <vscale x 2 x i64> [[WIDE_LOAD]]
; CHECK-NEXT: call void @llvm.vp.store.nxv2i64.p0(<vscale x 2 x i64> [[PREDPHI]], ptr align 8 [[TMP8]], <vscale x 2 x i1> splat (i1 true), i32 [[TMP12]])
; CHECK-NEXT: [[TMP13:%.*]] = zext i32 [[TMP12]] to i64
@@ -486,8 +485,7 @@ define void @predicated_sdiv(ptr noalias nocapture %a, i64 %v, i64 %n) {
; CHECK-NEXT: [[TMP8:%.*]] = getelementptr inbounds i64, ptr [[A:%.*]], i64 [[INDEX]]
; CHECK-NEXT: [[WIDE_LOAD:%.*]] = call <vscale x 2 x i64> @llvm.vp.load.nxv2i64.p0(ptr align 8 [[TMP8]], <vscale x 2 x i1> splat (i1 true), i32 [[TMP12]])
; CHECK-NEXT: [[TMP16:%.*]] = select <vscale x 2 x i1> [[TMP15]], <vscale x 2 x i1> [[TMP6]], <vscale x 2 x i1> zeroinitializer
-; CHECK-NEXT: [[TMP10:%.*]] = select <vscale x 2 x i1> [[TMP16]], <vscale x 2 x i64> [[BROADCAST_SPLAT]], <vscale x 2 x i64> splat (i64 1)
-; CHECK-NEXT: [[TMP11:%.*]] = sdiv <vscale x 2 x i64> [[WIDE_LOAD]], [[TMP10]]
+; CHECK-NEXT: [[TMP11:%.*]] = call <vscale x 2 x i64> @llvm.vp.sdiv.nxv2i64(<vscale x 2 x i64> [[WIDE_LOAD]], <vscale x 2 x i64> [[BROADCAST_SPLAT]], <vscale x 2 x i1> [[TMP6]], i32 [[TMP12]])
; CHECK-NEXT: [[PREDPHI:%.*]] = select <vscale x 2 x i1> [[TMP16]], <vscale x 2 x i64> [[TMP11]], <vscale x 2 x i64> [[WIDE_LOAD]]
; CHECK-NEXT: call void @llvm.vp.store.nxv2i64.p0(<vscale x 2 x i64> [[PREDPHI]], ptr align 8 [[TMP8]], <vscale x 2 x i1> splat (i1 true), i32 [[TMP12]])
; CHECK-NEXT: [[TMP13:%.*]] = zext i32 [[TMP12]] to i64
@@ -817,8 +815,7 @@ define void @predicated_sdiv_by_minus_one(ptr noalias nocapture %a, i64 %n) {
; CHECK-NEXT: [[WIDE_LOAD:%.*]] = call <vscale x 16 x i8> @llvm.vp.load.nxv16i8.p0(ptr align 1 [[TMP7]], <vscale x 16 x i1> splat (i1 true), i32 [[TMP12]])
; CHECK-NEXT: [[TMP9:%.*]] = icmp ne <vscale x 16 x i8> [[WIDE_LOAD]], splat (i8 -128)
; CHECK-NEXT: [[TMP16:%.*]] = select <vscale x 16 x i1> [[TMP15]], <vscale x 16 x i1> [[TMP9]], <vscale x 16 x i1> zeroinitializer
-; CHECK-NEXT: [[TMP10:%.*]] = select <vscale x 16 x i1> [[TMP16]], <vscale x 16 x i8> splat (i8 -1), <vscale x 16 x i8> splat (i8 1)
-; CHECK-NEXT: [[TMP11:%.*]] = sdiv <vscale x 16 x i8> [[WIDE_LOAD]], [[TMP10]]
+; CHECK-NEXT: [[TMP11:%.*]] = call <vscale x 16 x i8> @llvm.vp.sdiv.nxv16i8(<vscale x 16 x i8> [[WIDE_LOAD]], <vscale x 16 x i8> splat (i8 -1), <vscale x 16 x i1> [[TMP9]], i32 [[TMP12]])
; CHECK-NEXT: [[PREDPHI:%.*]] = select <vscale x 16 x i1> [[TMP16]], <vscale x 16 x i8> [[TMP11]], <vscale x 16 x i8> [[WIDE_LOAD]]
; CHECK-NEXT: call void @llvm.vp.store.nxv16i8.p0(<vscale x 16 x i8> [[PREDPHI]], ptr align 1 [[TMP7]], <vscale x 16 x i1> splat (i1 true), i32 [[TMP12]])
; CHECK-NEXT: [[TMP13:%.*]] = zext i32 [[TMP12]] to i64
diff --git a/llvm/test/Transforms/LoopVectorize/RISCV/tail-folding-div.ll b/llvm/test/Transforms/LoopVectorize/RISCV/tail-folding-div.ll
index 6b7fd976cbe6c..d13d4048561c4 100644
--- a/llvm/test/Transforms/LoopVectorize/RISCV/tail-folding-div.ll
+++ b/llvm/test/Transforms/LoopVectorize/RISCV/tail-folding-div.ll
@@ -22,8 +22,7 @@ define void @test_sdiv(ptr noalias %a, ptr noalias %b, ptr noalias %c) {
; IF-EVL-NEXT: [[VP_OP_LOAD:%.*]] = call <vscale x 2 x i64> @llvm.vp.load.nxv2i64.p0(ptr align 8 [[TMP7]], <vscale x 2 x i1> splat (i1 true), i32 [[TMP5]])
; IF-EVL-NEXT: [[TMP9:%.*]] = getelementptr i64, ptr [[B]], i64 [[EVL_BASED_IV]]
; IF-EVL-NEXT: [[VP_OP_LOAD1:%.*]] = call <vscale x 2 x i64> @llvm.vp.load.nxv2i64.p0(ptr align 8 [[TMP9]], <vscale x 2 x i1> splat (i1 true), i32 [[TMP5]])
-; IF-EVL-NEXT: [[TMP11:%.*]] = call <vscale x 2 x i64> @llvm.vp.merge.nxv2i64(<vscale x 2 x i1> splat (i1 true), <vscale x 2 x i64> [[VP_OP_LOAD1]], <vscale x 2 x i64> splat (i64 1), i32 [[TMP5]])
-; IF-EVL-NEXT: [[VP_OP:%.*]] = sdiv <vscale x 2 x i64> [[VP_OP_LOAD]], [[TMP11]]
+; IF-EVL-NEXT: [[VP_OP:%.*]] = call <vscale x 2 x i64> @llvm.vp.sdiv.nxv2i64(<vscale x 2 x i64> [[VP_OP_LOAD]], <vscale x 2 x i64> [[VP_OP_LOAD1]], <vscale x 2 x i1> splat (i1 true), i32 [[TMP5]])
; IF-EVL-NEXT: [[TMP12:%.*]] = getelementptr i64, ptr [[C]], i64 [[EVL_BASED_IV]]
; IF-EVL-NEXT: call void @llvm.vp.store.nxv2i64.p0(<vscale x 2 x i64> [[VP_OP]], ptr align 8 [[TMP12]], <vscale x 2 x i1> splat (i1 true), i32 [[TMP5]])
; IF-EVL-NEXT: [[TMP14:%.*]] = zext i32 [[TMP5]] to i64
@@ -132,8 +131,7 @@ define void @test_udiv(ptr noalias %a, ptr noalias %b, ptr noalias %c) {
; IF-EVL-NEXT: [[VP_OP_LOAD:%.*]] = call <vscale x 2 x i64> @llvm.vp.load.nxv2i64.p0(ptr align 8 [[TMP7]], <vscale x 2 x i1> splat (i1 true), i32 [[TMP5]])
; IF-EVL-NEXT: [[TMP9:%.*]] = getelementptr i64, ptr [[B]], i64 [[EVL_BASED_IV]]
; IF-EVL-NEXT: [[VP_OP_LOAD1:%.*]] = call <vscale x 2 x i64> @llvm.vp.load.nxv2i64.p0(ptr align 8 [[TMP9]], <vscale x 2 x i1> splat (i1 true), i32 [[TMP5]])
-; IF-EVL-NEXT: [[TMP11:%.*]] = call <vscale x 2 x i64> @llvm.vp.merge.nxv2i64(<vscale x 2 x i1> splat (i1 true), <vscale x 2 x i64> [[VP_OP_LOAD1]], <vscale x 2 x i64> splat (i64 1), i32 [[TMP5]])
-; IF-EVL-NEXT: [[VP_OP:%.*]] = udiv <vscale x 2 x i64> [[VP_OP_LOAD]], [[TMP11]]
+; IF-EVL-NEXT: [[VP_OP:%.*]] = call <vscale x 2 x i64> @llvm.vp.udiv.nxv2i64(<vscale x 2 x i64> [[VP_OP_LOAD]], <vscale x 2 x i64> [[VP_OP_LOAD1]], <vscale x 2 x i1> splat (i1 true), i32 [[TMP5]])
; IF-EVL-NEXT: [[TMP12:%.*]] = getelementptr i64, ptr [[C]], i64 [[EVL_BASED_IV]]
; IF-EVL-NEXT: call void @llvm.vp.store.nxv2i64.p0(<vscale x 2 x i64> [[VP_OP]], ptr align 8 [[TMP12]], <vscale x 2 x i1> splat (i1 true), i32 [[TMP5]])
; IF-EVL-NEXT: [[TMP14:%.*]] = zext i32 [[TMP5]] to i64
@@ -241,8 +239,7 @@ define void @test_srem(ptr noalias %a, ptr noalias %b, ptr noalias %c) {
; IF-EVL-NEXT: [[VP_OP_LOAD:%.*]] = call <vscale x 2 x i64> @llvm.vp.load.nxv2i64.p0(ptr align 8 [[TMP7]], <vscale x 2 x i1> splat (i1 true), i32 [[TMP5]])
; IF-EVL-NEXT: [[TMP9:%.*]] = getelementptr i64, ptr [[B]], i64 [[EVL_BASED_IV]]
; IF-EVL-NEXT: [[VP_OP_LOAD1:%.*]] = call <vscale x 2 x i64> @llvm.vp.load.nxv2i64.p0(ptr align 8 [[TMP9]], <vscale x 2 x i1> splat (i1 true), i32 [[TMP5]])
-; IF-EVL-NEXT: [[TMP11:%.*]] = call <vscale x 2 x i64> @llvm.vp.merge.nxv2i64(<vscale x 2 x i1> splat (i1 true), <vscale x 2 x i64> [[VP_OP_LOAD1]], <vscale x 2 x i64> splat (i64 1), i32 [[TMP5]])
-; IF-EVL-NEXT: [[VP_OP:%.*]] = srem <vscale x 2 x i64> [[VP_OP_LOAD]], [[TMP11]]
+; IF-EVL-NEXT: [[VP_OP:%.*]] = call <vscale x 2 x i64> @llvm.vp.srem.nxv2i64(<vscale x 2 x i64> [[VP_OP_LOAD]], <vscale x 2 x i64> [[VP_OP_LOAD1]], <vscale x 2 x i1> splat (i1 true), i32 [[TMP5]])
; IF-EVL-NEXT: [[TMP12:%.*]] = getelementptr i64, ptr [[C]], i64 [[EVL_BASED_IV]]
; IF-EVL-NEXT: call void @llvm.vp.store.nxv2i64.p0(<vscale x 2 x i64> [[VP_OP]], ptr align 8 [[TMP12]], <vscale x 2 x i1> splat (i1 true), i32 [[TMP5]])
; IF-EVL-NEXT: [[TMP14:%.*]] = zext i32 [[TMP5]] to i64
@@ -350,8 +347,7 @@ define void @test_urem(ptr noalias %a, ptr noalias %b, ptr noalias %c) {
; IF-EVL-NEXT: [[VP_OP_LOAD:%.*]] = call <vscale x 2 x i64> @llvm.vp.load.nxv2i64.p0(ptr align 8 [[TMP7]], <vscale x 2 x i1> splat (i1 true), i32 [[TMP5]])
; IF-EVL-NEXT: [[TMP9:%.*]] = getelementptr i64, ptr [[B]], i64 [[EVL_BASED_IV]]
; IF-EVL-NEXT: [[VP_OP_LOAD1:%.*]] = call <vscale x 2 x i64> @llvm.vp.load.nxv2i64.p0(ptr align 8 [[TMP9]], <vscale x 2 x i1> splat (i1 true), i32 [[TMP5]])
-; IF-EVL-NEXT: [[TMP11:%.*]] = call <vscale x 2 x i64> @llvm.vp.merge.nxv2i64(<vscale x 2 x i1> splat (i1 true), <vscale x 2 x i64> [[VP_OP_LOAD1]], <vscale x 2 x i64> splat (i64 1), i32 [[TMP5]])
-; IF-EVL-NEXT: [[VP_OP:%.*]] = urem <vscale x 2 x i64> [[VP_OP_LOAD]], [[TMP11]]
+; IF-EVL-NEXT: [[VP_OP:%.*]] = call <vscale x 2 x i64> @llvm.vp.urem.nxv2i64(<vscale x 2 x i64> [[VP_OP_LOAD]], <vscale x 2 x i64> [[VP_OP_LOAD1]], <vscale x 2 x i1> splat (i1 true), i32 [[TMP5]])
; IF-EVL-NEXT: [[TMP12:%.*]] = getelementptr i64, ptr [[C]], i64 [[EVL_BASED_IV]]
; IF-EVL-NEXT: call void @llvm.vp.store.nxv2i64.p0(<vscale x 2 x i64> [[VP_OP]], ptr align 8 [[TMP12]], <vscale x 2 x i1> splat (i1 true), i32 [[TMP5]])
; IF-EVL-NEXT: [[TMP14:%.*]] = zext i32 [[TMP5]] to i64
|
|
@llvm/pr-subscribers-backend-risc-v Author: Luke Lau (lukel97) ChangesIf a widened div or rem has a divisor that's not known to be non-zero, the potentially trapping lanes of the divisor are masked with ones. If the target is using EVL tail folding, we can instead mask those lanes with VP intrinsics. We can also further optimise this to remove the mask and instead use the EVL argument if the mask is exactly the header mask. This removes unnecessary vmv.v.is on RISC-V, and fixes #129538 Full diff: https://github.com/llvm/llvm-project/pull/154076.diff 5 Files Affected:
diff --git a/llvm/lib/Transforms/Vectorize/LoopVectorize.cpp b/llvm/lib/Transforms/Vectorize/LoopVectorize.cpp
index 675a230bd2c94..310e64eb7c615 100644
--- a/llvm/lib/Transforms/Vectorize/LoopVectorize.cpp
+++ b/llvm/lib/Transforms/Vectorize/LoopVectorize.cpp
@@ -7932,8 +7932,8 @@ bool VPRecipeBuilder::shouldWiden(Instruction *I, VFRange &Range) const {
Range);
}
-VPWidenRecipe *VPRecipeBuilder::tryToWiden(Instruction *I,
- ArrayRef<VPValue *> Operands) {
+VPRecipeWithIRFlags *VPRecipeBuilder::tryToWiden(Instruction *I,
+ ArrayRef<VPValue *> Operands) {
switch (I->getOpcode()) {
default:
return nullptr;
@@ -7941,11 +7941,23 @@ VPWidenRecipe *VPRecipeBuilder::tryToWiden(Instruction *I,
case Instruction::UDiv:
case Instruction::SRem:
case Instruction::URem: {
- // If not provably safe, use a select to form a safe divisor before widening the
- // div/rem operation itself. Otherwise fall through to general handling below.
+ // If not provably safe use a VP intrinsic to mask off trapping lanes if
+ // supported, or use a select to form a safe divisor before widening the
+ // div/rem operation itself.
+ // Otherwise fall through to general handling below.
if (CM.isPredicatedInst(I)) {
SmallVector<VPValue *> Ops(Operands);
VPValue *Mask = getBlockInMask(Builder.getInsertBlock());
+
+ if (CM.foldTailWithEVL()) {
+ Ops.push_back(Mask);
+ Ops.push_back(Plan.getOrAddLiveIn(ConstantInt::getAllOnesValue(
+ IntegerType::getInt32Ty(I->getContext()))));
+ return new VPWidenIntrinsicRecipe(
+ VPIntrinsic::getForOpcode(I->getOpcode()), Ops, I->getType(),
+ I->getDebugLoc());
+ }
+
VPValue *One =
Plan.getOrAddLiveIn(ConstantInt::get(I->getType(), 1u, false));
auto *SafeRHS = Builder.createSelect(Mask, Ops[1], One, I->getDebugLoc());
diff --git a/llvm/lib/Transforms/Vectorize/VPRecipeBuilder.h b/llvm/lib/Transforms/Vectorize/VPRecipeBuilder.h
index 41878e3c648e3..6696caefa3a04 100644
--- a/llvm/lib/Transforms/Vectorize/VPRecipeBuilder.h
+++ b/llvm/lib/Transforms/Vectorize/VPRecipeBuilder.h
@@ -121,7 +121,7 @@ class VPRecipeBuilder {
/// Check if \p I has an opcode that can be widened and return a VPWidenRecipe
/// if it can. The function should only be called if the cost-model indicates
/// that widening should be performed.
- VPWidenRecipe *tryToWiden(Instruction *I, ArrayRef<VPValue *> Operands);
+ VPRecipeWithIRFlags *tryToWiden(Instruction *I, ArrayRef<VPValue *> Operands);
/// Makes Histogram count operations safe for vectorization, by emitting a
/// llvm.experimental.vector.histogram.add intrinsic in place of the
diff --git a/llvm/lib/Transforms/Vectorize/VPlanTransforms.cpp b/llvm/lib/Transforms/Vectorize/VPlanTransforms.cpp
index de0c1e4d177bb..5300bdccadbb3 100644
--- a/llvm/lib/Transforms/Vectorize/VPlanTransforms.cpp
+++ b/llvm/lib/Transforms/Vectorize/VPlanTransforms.cpp
@@ -2174,6 +2174,29 @@ static VPRecipeBase *optimizeMaskToEVL(VPValue *HeaderMask,
Intrinsic::vp_merge, {&AllOneMask, LHS, RHS, &EVL},
TypeInfo.inferScalarType(LHS), VPI->getDebugLoc());
})
+ .Case<VPWidenIntrinsicRecipe>(
+ [&](VPWidenIntrinsicRecipe *VPI) -> VPRecipeBase * {
+ switch (VPI->getVectorIntrinsicID()) {
+ case Intrinsic::vp_udiv:
+ case Intrinsic::vp_sdiv:
+ case Intrinsic::vp_urem:
+ case Intrinsic::vp_srem:
+ break;
+ default:
+ return nullptr;
+ }
+ if (!match(VPI->getOperand(3), m_AllOnes()))
+ return nullptr;
+ VPValue *NewMask = GetNewMask(VPI->getOperand(2));
+ if (NewMask == HeaderMask)
+ return nullptr;
+ if (!NewMask)
+ NewMask = &AllOneMask;
+ return new VPWidenIntrinsicRecipe(
+ VPI->getVectorIntrinsicID(),
+ {VPI->getOperand(0), VPI->getOperand(1), NewMask, &EVL},
+ VPI->getResultType(), VPI->getDebugLoc());
+ })
.Default([&](VPRecipeBase *R) { return nullptr; });
}
diff --git a/llvm/test/Transforms/LoopVectorize/RISCV/divrem.ll b/llvm/test/Transforms/LoopVectorize/RISCV/divrem.ll
index 3af328fb6568e..e7900cc086a40 100644
--- a/llvm/test/Transforms/LoopVectorize/RISCV/divrem.ll
+++ b/llvm/test/Transforms/LoopVectorize/RISCV/divrem.ll
@@ -371,8 +371,7 @@ define void @predicated_udiv(ptr noalias nocapture %a, i64 %v, i64 %n) {
; CHECK-NEXT: [[TMP8:%.*]] = getelementptr inbounds i64, ptr [[A:%.*]], i64 [[INDEX]]
; CHECK-NEXT: [[WIDE_LOAD:%.*]] = call <vscale x 2 x i64> @llvm.vp.load.nxv2i64.p0(ptr align 8 [[TMP8]], <vscale x 2 x i1> splat (i1 true), i32 [[TMP12]])
; CHECK-NEXT: [[TMP16:%.*]] = select <vscale x 2 x i1> [[TMP15]], <vscale x 2 x i1> [[TMP6]], <vscale x 2 x i1> zeroinitializer
-; CHECK-NEXT: [[TMP10:%.*]] = select <vscale x 2 x i1> [[TMP16]], <vscale x 2 x i64> [[BROADCAST_SPLAT]], <vscale x 2 x i64> splat (i64 1)
-; CHECK-NEXT: [[TMP11:%.*]] = udiv <vscale x 2 x i64> [[WIDE_LOAD]], [[TMP10]]
+; CHECK-NEXT: [[TMP11:%.*]] = call <vscale x 2 x i64> @llvm.vp.udiv.nxv2i64(<vscale x 2 x i64> [[WIDE_LOAD]], <vscale x 2 x i64> [[BROADCAST_SPLAT]], <vscale x 2 x i1> [[TMP6]], i32 [[TMP12]])
; CHECK-NEXT: [[PREDPHI:%.*]] = select <vscale x 2 x i1> [[TMP16]], <vscale x 2 x i64> [[TMP11]], <vscale x 2 x i64> [[WIDE_LOAD]]
; CHECK-NEXT: call void @llvm.vp.store.nxv2i64.p0(<vscale x 2 x i64> [[PREDPHI]], ptr align 8 [[TMP8]], <vscale x 2 x i1> splat (i1 true), i32 [[TMP12]])
; CHECK-NEXT: [[TMP13:%.*]] = zext i32 [[TMP12]] to i64
@@ -486,8 +485,7 @@ define void @predicated_sdiv(ptr noalias nocapture %a, i64 %v, i64 %n) {
; CHECK-NEXT: [[TMP8:%.*]] = getelementptr inbounds i64, ptr [[A:%.*]], i64 [[INDEX]]
; CHECK-NEXT: [[WIDE_LOAD:%.*]] = call <vscale x 2 x i64> @llvm.vp.load.nxv2i64.p0(ptr align 8 [[TMP8]], <vscale x 2 x i1> splat (i1 true), i32 [[TMP12]])
; CHECK-NEXT: [[TMP16:%.*]] = select <vscale x 2 x i1> [[TMP15]], <vscale x 2 x i1> [[TMP6]], <vscale x 2 x i1> zeroinitializer
-; CHECK-NEXT: [[TMP10:%.*]] = select <vscale x 2 x i1> [[TMP16]], <vscale x 2 x i64> [[BROADCAST_SPLAT]], <vscale x 2 x i64> splat (i64 1)
-; CHECK-NEXT: [[TMP11:%.*]] = sdiv <vscale x 2 x i64> [[WIDE_LOAD]], [[TMP10]]
+; CHECK-NEXT: [[TMP11:%.*]] = call <vscale x 2 x i64> @llvm.vp.sdiv.nxv2i64(<vscale x 2 x i64> [[WIDE_LOAD]], <vscale x 2 x i64> [[BROADCAST_SPLAT]], <vscale x 2 x i1> [[TMP6]], i32 [[TMP12]])
; CHECK-NEXT: [[PREDPHI:%.*]] = select <vscale x 2 x i1> [[TMP16]], <vscale x 2 x i64> [[TMP11]], <vscale x 2 x i64> [[WIDE_LOAD]]
; CHECK-NEXT: call void @llvm.vp.store.nxv2i64.p0(<vscale x 2 x i64> [[PREDPHI]], ptr align 8 [[TMP8]], <vscale x 2 x i1> splat (i1 true), i32 [[TMP12]])
; CHECK-NEXT: [[TMP13:%.*]] = zext i32 [[TMP12]] to i64
@@ -817,8 +815,7 @@ define void @predicated_sdiv_by_minus_one(ptr noalias nocapture %a, i64 %n) {
; CHECK-NEXT: [[WIDE_LOAD:%.*]] = call <vscale x 16 x i8> @llvm.vp.load.nxv16i8.p0(ptr align 1 [[TMP7]], <vscale x 16 x i1> splat (i1 true), i32 [[TMP12]])
; CHECK-NEXT: [[TMP9:%.*]] = icmp ne <vscale x 16 x i8> [[WIDE_LOAD]], splat (i8 -128)
; CHECK-NEXT: [[TMP16:%.*]] = select <vscale x 16 x i1> [[TMP15]], <vscale x 16 x i1> [[TMP9]], <vscale x 16 x i1> zeroinitializer
-; CHECK-NEXT: [[TMP10:%.*]] = select <vscale x 16 x i1> [[TMP16]], <vscale x 16 x i8> splat (i8 -1), <vscale x 16 x i8> splat (i8 1)
-; CHECK-NEXT: [[TMP11:%.*]] = sdiv <vscale x 16 x i8> [[WIDE_LOAD]], [[TMP10]]
+; CHECK-NEXT: [[TMP11:%.*]] = call <vscale x 16 x i8> @llvm.vp.sdiv.nxv16i8(<vscale x 16 x i8> [[WIDE_LOAD]], <vscale x 16 x i8> splat (i8 -1), <vscale x 16 x i1> [[TMP9]], i32 [[TMP12]])
; CHECK-NEXT: [[PREDPHI:%.*]] = select <vscale x 16 x i1> [[TMP16]], <vscale x 16 x i8> [[TMP11]], <vscale x 16 x i8> [[WIDE_LOAD]]
; CHECK-NEXT: call void @llvm.vp.store.nxv16i8.p0(<vscale x 16 x i8> [[PREDPHI]], ptr align 1 [[TMP7]], <vscale x 16 x i1> splat (i1 true), i32 [[TMP12]])
; CHECK-NEXT: [[TMP13:%.*]] = zext i32 [[TMP12]] to i64
diff --git a/llvm/test/Transforms/LoopVectorize/RISCV/tail-folding-div.ll b/llvm/test/Transforms/LoopVectorize/RISCV/tail-folding-div.ll
index 6b7fd976cbe6c..d13d4048561c4 100644
--- a/llvm/test/Transforms/LoopVectorize/RISCV/tail-folding-div.ll
+++ b/llvm/test/Transforms/LoopVectorize/RISCV/tail-folding-div.ll
@@ -22,8 +22,7 @@ define void @test_sdiv(ptr noalias %a, ptr noalias %b, ptr noalias %c) {
; IF-EVL-NEXT: [[VP_OP_LOAD:%.*]] = call <vscale x 2 x i64> @llvm.vp.load.nxv2i64.p0(ptr align 8 [[TMP7]], <vscale x 2 x i1> splat (i1 true), i32 [[TMP5]])
; IF-EVL-NEXT: [[TMP9:%.*]] = getelementptr i64, ptr [[B]], i64 [[EVL_BASED_IV]]
; IF-EVL-NEXT: [[VP_OP_LOAD1:%.*]] = call <vscale x 2 x i64> @llvm.vp.load.nxv2i64.p0(ptr align 8 [[TMP9]], <vscale x 2 x i1> splat (i1 true), i32 [[TMP5]])
-; IF-EVL-NEXT: [[TMP11:%.*]] = call <vscale x 2 x i64> @llvm.vp.merge.nxv2i64(<vscale x 2 x i1> splat (i1 true), <vscale x 2 x i64> [[VP_OP_LOAD1]], <vscale x 2 x i64> splat (i64 1), i32 [[TMP5]])
-; IF-EVL-NEXT: [[VP_OP:%.*]] = sdiv <vscale x 2 x i64> [[VP_OP_LOAD]], [[TMP11]]
+; IF-EVL-NEXT: [[VP_OP:%.*]] = call <vscale x 2 x i64> @llvm.vp.sdiv.nxv2i64(<vscale x 2 x i64> [[VP_OP_LOAD]], <vscale x 2 x i64> [[VP_OP_LOAD1]], <vscale x 2 x i1> splat (i1 true), i32 [[TMP5]])
; IF-EVL-NEXT: [[TMP12:%.*]] = getelementptr i64, ptr [[C]], i64 [[EVL_BASED_IV]]
; IF-EVL-NEXT: call void @llvm.vp.store.nxv2i64.p0(<vscale x 2 x i64> [[VP_OP]], ptr align 8 [[TMP12]], <vscale x 2 x i1> splat (i1 true), i32 [[TMP5]])
; IF-EVL-NEXT: [[TMP14:%.*]] = zext i32 [[TMP5]] to i64
@@ -132,8 +131,7 @@ define void @test_udiv(ptr noalias %a, ptr noalias %b, ptr noalias %c) {
; IF-EVL-NEXT: [[VP_OP_LOAD:%.*]] = call <vscale x 2 x i64> @llvm.vp.load.nxv2i64.p0(ptr align 8 [[TMP7]], <vscale x 2 x i1> splat (i1 true), i32 [[TMP5]])
; IF-EVL-NEXT: [[TMP9:%.*]] = getelementptr i64, ptr [[B]], i64 [[EVL_BASED_IV]]
; IF-EVL-NEXT: [[VP_OP_LOAD1:%.*]] = call <vscale x 2 x i64> @llvm.vp.load.nxv2i64.p0(ptr align 8 [[TMP9]], <vscale x 2 x i1> splat (i1 true), i32 [[TMP5]])
-; IF-EVL-NEXT: [[TMP11:%.*]] = call <vscale x 2 x i64> @llvm.vp.merge.nxv2i64(<vscale x 2 x i1> splat (i1 true), <vscale x 2 x i64> [[VP_OP_LOAD1]], <vscale x 2 x i64> splat (i64 1), i32 [[TMP5]])
-; IF-EVL-NEXT: [[VP_OP:%.*]] = udiv <vscale x 2 x i64> [[VP_OP_LOAD]], [[TMP11]]
+; IF-EVL-NEXT: [[VP_OP:%.*]] = call <vscale x 2 x i64> @llvm.vp.udiv.nxv2i64(<vscale x 2 x i64> [[VP_OP_LOAD]], <vscale x 2 x i64> [[VP_OP_LOAD1]], <vscale x 2 x i1> splat (i1 true), i32 [[TMP5]])
; IF-EVL-NEXT: [[TMP12:%.*]] = getelementptr i64, ptr [[C]], i64 [[EVL_BASED_IV]]
; IF-EVL-NEXT: call void @llvm.vp.store.nxv2i64.p0(<vscale x 2 x i64> [[VP_OP]], ptr align 8 [[TMP12]], <vscale x 2 x i1> splat (i1 true), i32 [[TMP5]])
; IF-EVL-NEXT: [[TMP14:%.*]] = zext i32 [[TMP5]] to i64
@@ -241,8 +239,7 @@ define void @test_srem(ptr noalias %a, ptr noalias %b, ptr noalias %c) {
; IF-EVL-NEXT: [[VP_OP_LOAD:%.*]] = call <vscale x 2 x i64> @llvm.vp.load.nxv2i64.p0(ptr align 8 [[TMP7]], <vscale x 2 x i1> splat (i1 true), i32 [[TMP5]])
; IF-EVL-NEXT: [[TMP9:%.*]] = getelementptr i64, ptr [[B]], i64 [[EVL_BASED_IV]]
; IF-EVL-NEXT: [[VP_OP_LOAD1:%.*]] = call <vscale x 2 x i64> @llvm.vp.load.nxv2i64.p0(ptr align 8 [[TMP9]], <vscale x 2 x i1> splat (i1 true), i32 [[TMP5]])
-; IF-EVL-NEXT: [[TMP11:%.*]] = call <vscale x 2 x i64> @llvm.vp.merge.nxv2i64(<vscale x 2 x i1> splat (i1 true), <vscale x 2 x i64> [[VP_OP_LOAD1]], <vscale x 2 x i64> splat (i64 1), i32 [[TMP5]])
-; IF-EVL-NEXT: [[VP_OP:%.*]] = srem <vscale x 2 x i64> [[VP_OP_LOAD]], [[TMP11]]
+; IF-EVL-NEXT: [[VP_OP:%.*]] = call <vscale x 2 x i64> @llvm.vp.srem.nxv2i64(<vscale x 2 x i64> [[VP_OP_LOAD]], <vscale x 2 x i64> [[VP_OP_LOAD1]], <vscale x 2 x i1> splat (i1 true), i32 [[TMP5]])
; IF-EVL-NEXT: [[TMP12:%.*]] = getelementptr i64, ptr [[C]], i64 [[EVL_BASED_IV]]
; IF-EVL-NEXT: call void @llvm.vp.store.nxv2i64.p0(<vscale x 2 x i64> [[VP_OP]], ptr align 8 [[TMP12]], <vscale x 2 x i1> splat (i1 true), i32 [[TMP5]])
; IF-EVL-NEXT: [[TMP14:%.*]] = zext i32 [[TMP5]] to i64
@@ -350,8 +347,7 @@ define void @test_urem(ptr noalias %a, ptr noalias %b, ptr noalias %c) {
; IF-EVL-NEXT: [[VP_OP_LOAD:%.*]] = call <vscale x 2 x i64> @llvm.vp.load.nxv2i64.p0(ptr align 8 [[TMP7]], <vscale x 2 x i1> splat (i1 true), i32 [[TMP5]])
; IF-EVL-NEXT: [[TMP9:%.*]] = getelementptr i64, ptr [[B]], i64 [[EVL_BASED_IV]]
; IF-EVL-NEXT: [[VP_OP_LOAD1:%.*]] = call <vscale x 2 x i64> @llvm.vp.load.nxv2i64.p0(ptr align 8 [[TMP9]], <vscale x 2 x i1> splat (i1 true), i32 [[TMP5]])
-; IF-EVL-NEXT: [[TMP11:%.*]] = call <vscale x 2 x i64> @llvm.vp.merge.nxv2i64(<vscale x 2 x i1> splat (i1 true), <vscale x 2 x i64> [[VP_OP_LOAD1]], <vscale x 2 x i64> splat (i64 1), i32 [[TMP5]])
-; IF-EVL-NEXT: [[VP_OP:%.*]] = urem <vscale x 2 x i64> [[VP_OP_LOAD]], [[TMP11]]
+; IF-EVL-NEXT: [[VP_OP:%.*]] = call <vscale x 2 x i64> @llvm.vp.urem.nxv2i64(<vscale x 2 x i64> [[VP_OP_LOAD]], <vscale x 2 x i64> [[VP_OP_LOAD1]], <vscale x 2 x i1> splat (i1 true), i32 [[TMP5]])
; IF-EVL-NEXT: [[TMP12:%.*]] = getelementptr i64, ptr [[C]], i64 [[EVL_BASED_IV]]
; IF-EVL-NEXT: call void @llvm.vp.store.nxv2i64.p0(<vscale x 2 x i64> [[VP_OP]], ptr align 8 [[TMP12]], <vscale x 2 x i1> splat (i1 true), i32 [[TMP5]])
; IF-EVL-NEXT: [[TMP14:%.*]] = zext i32 [[TMP5]] to i64
|
|
I think this approach should be fine in the end. But at the current stage, if we do it this way, won’t any VPTransform optimizations targeting VPWidenRecipe div/rem become ineffective? |
fhahn
reviewed
Aug 18, 2025
There was a problem hiding this comment.
Hmm, I think it would be best to avoid introducing this early, as this seems inconsistent with how tail-folding with EVL is handled.
I think we could still run into the same issue as with #148828 (e.g. consider a transform that can prove all divisors are != for all loop iterations.
For #148828, we should be able to check if all users are safe, no?
Yeah, but practically speaking I'm not aware of many optimisations on div/rem that kick in when we're masking off the divisor anyway.
This isn't actually EVL tail folding specific. We could also do this for non tail folded loops, I just couldn't find a good TTI hook to check if VP intrinsics were supported or not.
Should this be != 0 for all loop iterations?
We could check that none of the users trap on poison (i.e. are also divs/rems), but I don't think that really addresses the other issue of whether or not the poison lanes are used by other recipes. This PR removes the need to assume the latter by introducing poison when we already know the mask for the block. As for checking that none of the users trap on poison in this PR, my understanding is that we need to worry about that because we mask off those recipes (i.e. div/rems) anyway? |
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If a widened div or rem has a divisor that's not known to be non-zero, the potentially trapping lanes of the divisor are masked with ones.
If the target is using EVL tail folding, we can instead mask those lanes with VP intrinsics.
We can also further optimise this to remove the mask and instead use the EVL argument if the mask is exactly the header mask.
This removes unnecessary vmv.v.is on RISC-V, and fixes #129538