[llvm] 4f3b1c6 - [IRBuilder] Fix CreateFDivFMF ignoring source FMF

[Nikita Popov via llvm-commits]

Author: Daniel Woodworth
Date: 2022-12-13T11:35:17+01:00
New Revision: 4f3b1c6dd6ef6c7b5bb79f058e3b7ba4bcdf4566

URL: https://github.com/llvm/llvm-project/commit/4f3b1c6dd6ef6c7b5bb79f058e3b7ba4bcdf4566
DIFF: https://github.com/llvm/llvm-project/commit/4f3b1c6dd6ef6c7b5bb79f058e3b7ba4bcdf4566.diff

LOG: [IRBuilder] Fix CreateFDivFMF ignoring source FMF

This change fixes a small bug in IRBuilderBase::CreateFDivFMF introduced
by accident in rGf34dcf27637f which caused the builder's default fast math
flags to be used for the new fdiv instruction instead of the ones from
the source instruction. It also adds unit testing for the CreateF*FMF
family of functions to more easily catch similar bugs in the future.

Differential Revision: https://reviews.llvm.org/D139583

Added: 
    

Modified: 
    llvm/include/llvm/IR/IRBuilder.h
    llvm/unittests/IR/IRBuilderTest.cpp

Removed: 
    


################################################################################
diff  --git a/llvm/include/llvm/IR/IRBuilder.h b/llvm/include/llvm/IR/IRBuilder.h
index 6da83e99130af..44baf639bbb24 100644
--- a/llvm/include/llvm/IR/IRBuilder.h
+++ b/llvm/include/llvm/IR/IRBuilder.h
@@ -1543,6 +1543,7 @@ class IRBuilderBase {
       return CreateConstrainedFPBinOp(Intrinsic::experimental_constrained_fdiv,
                                       L, R, FMFSource, Name);
 
+    FastMathFlags FMF = FMFSource->getFastMathFlags();
     if (Value *V = Folder.FoldBinOpFMF(Instruction::FDiv, L, R, FMF))
       return V;
     Instruction *I = setFPAttrs(BinaryOperator::CreateFDiv(L, R), nullptr, FMF);

diff  --git a/llvm/unittests/IR/IRBuilderTest.cpp b/llvm/unittests/IR/IRBuilderTest.cpp
index 32e7b65d3ff6a..ef5f974419029 100644
--- a/llvm/unittests/IR/IRBuilderTest.cpp
+++ b/llvm/unittests/IR/IRBuilderTest.cpp
@@ -551,7 +551,7 @@ TEST_F(IRBuilderTest, UnaryOperators) {
 TEST_F(IRBuilderTest, FastMathFlags) {
   IRBuilder<> Builder(BB);
   Value *F, *FC;
-  Instruction *FDiv, *FAdd, *FCmp, *FCall;
+  Instruction *FDiv, *FAdd, *FCmp, *FCall, *FNeg, *FSub, *FMul, *FRem;
 
   F = Builder.CreateLoad(GV->getValueType(), GV);
   F = Builder.CreateFAdd(F, F);
@@ -732,6 +732,36 @@ TEST_F(IRBuilderTest, FastMathFlags) {
   EXPECT_TRUE(FDiv->hasNoNaNs());
   EXPECT_FALSE(FDiv->hasAllowReciprocal());
 
+  // Test that CreateF*FMF functions copy flags from the source instruction
+  // instead of using the builder default.
+  Instruction *const FMFSource = FAdd;
+  EXPECT_FALSE(Builder.getFastMathFlags().noNaNs());
+  EXPECT_TRUE(FMFSource->hasNoNaNs());
+
+  F = Builder.CreateFNegFMF(F, FMFSource);
+  ASSERT_TRUE(isa<Instruction>(F));
+  FNeg = cast<Instruction>(F);
+  EXPECT_TRUE(FNeg->hasNoNaNs());
+  F = Builder.CreateFAddFMF(F, F, FMFSource);
+  ASSERT_TRUE(isa<Instruction>(F));
+  FAdd = cast<Instruction>(F);
+  EXPECT_TRUE(FAdd->hasNoNaNs());
+  F = Builder.CreateFSubFMF(F, F, FMFSource);
+  ASSERT_TRUE(isa<Instruction>(F));
+  FSub = cast<Instruction>(F);
+  EXPECT_TRUE(FSub->hasNoNaNs());
+  F = Builder.CreateFMulFMF(F, F, FMFSource);
+  ASSERT_TRUE(isa<Instruction>(F));
+  FMul = cast<Instruction>(F);
+  EXPECT_TRUE(FMul->hasNoNaNs());
+  F = Builder.CreateFDivFMF(F, F, FMFSource);
+  ASSERT_TRUE(isa<Instruction>(F));
+  FDiv = cast<Instruction>(F);
+  EXPECT_TRUE(FDiv->hasNoNaNs());
+  F = Builder.CreateFRemFMF(F, F, FMFSource);
+  ASSERT_TRUE(isa<Instruction>(F));
+  FRem = cast<Instruction>(F);
+  EXPECT_TRUE(FRem->hasNoNaNs());
 }
 
 TEST_F(IRBuilderTest, WrapFlags) {