[llvm] [InstCombine] Fold shuffles through all trivially vectorizable intrinsics (PR #141979)

[via llvm-commits]

llvmbot wrote:


<!--LLVM PR SUMMARY COMMENT-->

@llvm/pr-subscribers-llvm-transforms

Author: Luke Lau (lukel97)

<details>
<summary>Changes</summary>

This addresses a TODO in foldShuffledIntrinsicOperands to use isTriviallyVectorizable instead of a hardcoded list of intrinsics, which in turn allows more intriniscs to be scalarized by VectorCombine.

>From what I can tell every intrinsic here should be speculatable so an assertion was added.

Because this enables intrinsics like abs which have a scalar operand, we need to also check isVectorIntrinsicWithScalarOpAtArg.



---
Full diff: https://github.com/llvm/llvm-project/pull/141979.diff


4 Files Affected:

- (modified) llvm/lib/Transforms/InstCombine/InstCombineCalls.cpp (+22-19) 
- (modified) llvm/test/Transforms/InstCombine/abs-1.ll (+11) 
- (modified) llvm/test/Transforms/InstCombine/fma.ll (+13) 
- (modified) llvm/test/Transforms/InstCombine/sqrt.ll (+11) 


``````````diff
diff --git a/llvm/lib/Transforms/InstCombine/InstCombineCalls.cpp b/llvm/lib/Transforms/InstCombine/InstCombineCalls.cpp
index e101edf4a6208..5eb466f6c6df1 100644
--- a/llvm/lib/Transforms/InstCombine/InstCombineCalls.cpp
+++ b/llvm/lib/Transforms/InstCombine/InstCombineCalls.cpp
@@ -1401,26 +1401,25 @@ static Instruction *factorizeMinMaxTree(IntrinsicInst *II) {
 /// try to shuffle after the intrinsic.
 Instruction *
 InstCombinerImpl::foldShuffledIntrinsicOperands(IntrinsicInst *II) {
-  // TODO: This should be extended to handle other intrinsics like fshl, ctpop,
-  //       etc. Use llvm::isTriviallyVectorizable() and related to determine
-  //       which intrinsics are safe to shuffle?
-  switch (II->getIntrinsicID()) {
-  case Intrinsic::smax:
-  case Intrinsic::smin:
-  case Intrinsic::umax:
-  case Intrinsic::umin:
-  case Intrinsic::fma:
-  case Intrinsic::fshl:
-  case Intrinsic::fshr:
-    break;
-  default:
+  if (!isTriviallyVectorizable(II->getIntrinsicID()))
+    return nullptr;
+
+  assert(isSafeToSpeculativelyExecute(II) &&
+         "Trivially vectorizable but not safe to speculatively execute?");
+
+  // fabs is canonicalized to fabs (shuffle ...) in foldShuffleOfUnaryOps, so
+  // avoid undoing it.
+  if (match(II, m_FAbs(m_Value())))
     return nullptr;
-  }
 
   Value *X;
   Constant *C;
   ArrayRef<int> Mask;
-  auto *NonConstArg = find_if_not(II->args(), IsaPred<Constant>);
+  auto *NonConstArg = find_if_not(II->args(), [&II](Use &Arg) {
+    return isa<Constant>(Arg.get()) ||
+           isVectorIntrinsicWithScalarOpAtArg(II->getIntrinsicID(),
+                                              Arg.getOperandNo(), nullptr);
+  });
   if (!NonConstArg ||
       !match(NonConstArg, m_Shuffle(m_Value(X), m_Poison(), m_Mask(Mask))))
     return nullptr;
@@ -1432,11 +1431,15 @@ InstCombinerImpl::foldShuffledIntrinsicOperands(IntrinsicInst *II) {
   // See if all arguments are shuffled with the same mask.
   SmallVector<Value *, 4> NewArgs;
   Type *SrcTy = X->getType();
-  for (Value *Arg : II->args()) {
-    if (match(Arg, m_Shuffle(m_Value(X), m_Poison(), m_SpecificMask(Mask))) &&
-        X->getType() == SrcTy)
+  for (Use &Arg : II->args()) {
+    if (isVectorIntrinsicWithScalarOpAtArg(II->getIntrinsicID(),
+                                           Arg.getOperandNo(), nullptr))
+      NewArgs.push_back(Arg);
+    else if (match(&Arg,
+                   m_Shuffle(m_Value(X), m_Poison(), m_SpecificMask(Mask))) &&
+             X->getType() == SrcTy)
       NewArgs.push_back(X);
-    else if (match(Arg, m_ImmConstant(C))) {
+    else if (match(&Arg, m_ImmConstant(C))) {
       // If it's a constant, try find the constant that would be shuffled to C.
       if (Constant *ShuffledC =
               unshuffleConstant(Mask, C, cast<VectorType>(SrcTy)))
diff --git a/llvm/test/Transforms/InstCombine/abs-1.ll b/llvm/test/Transforms/InstCombine/abs-1.ll
index 7037647d116ba..fd67fc3421498 100644
--- a/llvm/test/Transforms/InstCombine/abs-1.ll
+++ b/llvm/test/Transforms/InstCombine/abs-1.ll
@@ -978,3 +978,14 @@ define i32 @abs_diff_signed_slt_no_nsw_swap(i32 %a, i32 %b) {
   %cond = select i1 %cmp, i32 %sub_ba, i32 %sub_ab
   ret i32 %cond
 }
+
+define <2 x i32> @abs_unary_shuffle_ops(<2 x i32> %x) {
+; CHECK-LABEL: @abs_unary_shuffle_ops(
+; CHECK-NEXT:    [[R2:%.*]] = call <2 x i32> @llvm.abs.v2i32(<2 x i32> [[R1:%.*]], i1 false)
+; CHECK-NEXT:    [[R:%.*]] = shufflevector <2 x i32> [[R2]], <2 x i32> poison, <2 x i32> <i32 1, i32 0>
+; CHECK-NEXT:    ret <2 x i32> [[R]]
+;
+  %a = shufflevector <2 x i32> %x, <2 x i32> poison, <2 x i32> <i32 1, i32 0>
+  %r = call <2 x i32> @llvm.abs(<2 x i32> %a, i1 false)
+  ret <2 x i32> %r
+}
diff --git a/llvm/test/Transforms/InstCombine/fma.ll b/llvm/test/Transforms/InstCombine/fma.ll
index f0d4f776a5d90..e3d3e722bcc23 100644
--- a/llvm/test/Transforms/InstCombine/fma.ll
+++ b/llvm/test/Transforms/InstCombine/fma.ll
@@ -972,6 +972,19 @@ define <2 x half> @fma_negone_vec_partial_undef(<2 x half> %x, <2 x half> %y) {
   ret <2 x half> %sub
 }
 
+define <2 x float> @fmuladd_unary_shuffle_ops(<2 x float> %x, <2 x float> %y, <2 x float> %z) {
+; CHECK-LABEL: @fmuladd_unary_shuffle_ops(
+; CHECK-NEXT:    [[R:%.*]] = call <2 x float> @llvm.fmuladd.v2f32(<2 x float> [[A:%.*]], <2 x float> [[B:%.*]], <2 x float> [[C:%.*]])
+; CHECK-NEXT:    [[R1:%.*]] = shufflevector <2 x float> [[R]], <2 x float> poison, <2 x i32> <i32 1, i32 0>
+; CHECK-NEXT:    ret <2 x float> [[R1]]
+;
+  %a = shufflevector <2 x float> %x, <2 x float> poison, <2 x i32> <i32 1, i32 0>
+  %b = shufflevector <2 x float> %y, <2 x float> poison, <2 x i32> <i32 1, i32 0>
+  %c = shufflevector <2 x float> %z, <2 x float> poison, <2 x i32> <i32 1, i32 0>
+  %r = call <2 x float> @llvm.fmuladd(<2 x float> %a, <2 x float> %b, <2 x float> %c)
+  ret <2 x float> %r
+}
+
 ; negative tests
 
 define half @fma_non_negone(half %x, half %y) {
diff --git a/llvm/test/Transforms/InstCombine/sqrt.ll b/llvm/test/Transforms/InstCombine/sqrt.ll
index 0f4db3b3a65ae..2fda5bc37d023 100644
--- a/llvm/test/Transforms/InstCombine/sqrt.ll
+++ b/llvm/test/Transforms/InstCombine/sqrt.ll
@@ -201,6 +201,17 @@ define <2 x float> @sqrt_exp_vec(<2 x float> %x) {
   ret <2 x float> %res
 }
 
+define <2 x float> @sqrt_unary_shuffle_ops(<2 x float> %x) {
+; CHECK-LABEL: @sqrt_unary_shuffle_ops(
+; CHECK-NEXT:    [[R:%.*]] = call <2 x float> @llvm.sqrt.v2f32(<2 x float> [[A:%.*]])
+; CHECK-NEXT:    [[R1:%.*]] = shufflevector <2 x float> [[R]], <2 x float> poison, <2 x i32> <i32 1, i32 0>
+; CHECK-NEXT:    ret <2 x float> [[R1]]
+;
+  %a = shufflevector <2 x float> %x, <2 x float> poison, <2 x i32> <i32 1, i32 0>
+  %r = call <2 x float> @llvm.sqrt(<2 x float> %a)
+  ret <2 x float> %r
+}
+
 declare i32 @foo(double)
 declare double @sqrt(double) readnone
 declare float @sqrtf(float)

``````````

</details>


https://github.com/llvm/llvm-project/pull/141979