[PATCH] D141214: [InstCombine] Don't combine smul of i1 type constant one

[luxufan via Phabricator via llvm-commits]

StephenFan created this revision.
StephenFan added reviewers: nikic, spatel.
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Fixes: https://github.com/llvm/llvm-project/issues/59876


Repository:
  rG LLVM Github Monorepo

https://reviews.llvm.org/D141214

Files:
  llvm/lib/Transforms/InstCombine/InstCombineCompares.cpp
  llvm/test/Transforms/InstCombine/mul.ll


Index: llvm/test/Transforms/InstCombine/mul.ll
===================================================================
--- llvm/test/Transforms/InstCombine/mul.ll
+++ llvm/test/Transforms/InstCombine/mul.ll
@@ -1761,3 +1761,24 @@
   %r = mul i32 %zx, -16777216 ; -1 << 24
   ret i32 %r
 }
+
+declare { i1, i1 } @llvm.smul.with.overflow.i1(i1, i1)
+declare { i1, i1 } @llvm.umul.with.overflow.i1(i1, i1)
+
+define i1 @smul_i1_one(i1 %A) {
+; CHECK-LABEL: @smul_i1_one(
+; CHECK-NEXT:    ret i1 [[A:%.*]]
+;
+  %C = call {i1, i1} @llvm.smul.with.overflow.i1(i1 %A, i1 1)
+  %D = extractvalue {i1, i1} %C, 1
+  ret i1 %D
+}
+
+define i1 @umul_i1_one(i1 %A) {
+; CHECK-LABEL: @umul_i1_one(
+; CHECK-NEXT:    ret i1 false
+;
+  %C = call {i1, i1} @llvm.umul.with.overflow.i1(i1 %A, i1 1)
+  %D = extractvalue {i1, i1} %C, 1
+  ret i1 %D
+}
Index: llvm/lib/Transforms/InstCombine/InstCombineCompares.cpp
===================================================================
--- llvm/lib/Transforms/InstCombine/InstCombineCompares.cpp
+++ llvm/lib/Transforms/InstCombine/InstCombineCompares.cpp
@@ -4988,7 +4988,7 @@
   return foldICmpWithZextOrSext(ICmp);
 }
 
-static bool isNeutralValue(Instruction::BinaryOps BinaryOp, Value *RHS) {
+static bool isNeutralValue(Instruction::BinaryOps BinaryOp, Value *RHS, bool IsSigned) {
   switch (BinaryOp) {
     default:
       llvm_unreachable("Unsupported binary op");
@@ -4996,7 +4996,8 @@
     case Instruction::Sub:
       return match(RHS, m_Zero());
     case Instruction::Mul:
-      return match(RHS, m_One());
+      return !(RHS->getType()->isIntegerTy(1) && IsSigned) &&
+             match(RHS, m_One());
   }
 }
 
@@ -5043,7 +5044,7 @@
   if (auto *LHSTy = dyn_cast<VectorType>(LHS->getType()))
     OverflowTy = VectorType::get(OverflowTy, LHSTy->getElementCount());
 
-  if (isNeutralValue(BinaryOp, RHS)) {
+  if (isNeutralValue(BinaryOp, RHS, IsSigned)) {
     Result = LHS;
     Overflow = ConstantInt::getFalse(OverflowTy);
     return true;


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