From ebf9bf2cbc8fa68d536e481e370c4ba40ce61a8a Mon Sep 17 00:00:00 2001 From: Sanjay Patel Date: Sun, 17 Nov 2019 11:23:44 -0500 Subject: [SimplifyCFG] propagate fast-math-flags (FMF) from phi to select Similar to/extension of D70208 (rGee0882bdf866), but this one may finally allow closing motivating bugs. This is another step towards having FMF apply only to FP values rather than those + fcmp. See PR38086 for one of the original discussions/motivations: https://bugs.llvm.org/show_bug.cgi?id=38086 And the test here is derived from PR39535: https://bugs.llvm.org/show_bug.cgi?id=39535 Currently, we lose FMF when converting any phi to select in SimplifyCFG. There are a small number of similar changes needed to correct within SimplifyCFG, so it should be quick to patch this pass up. FMF was extended to select and phi with: D61917 D67564 --- llvm/lib/Transforms/Utils/SimplifyCFG.cpp | 5 +++++ 1 file changed, 5 insertions(+) (limited to 'llvm/lib/Transforms/Utils/SimplifyCFG.cpp') diff --git a/llvm/lib/Transforms/Utils/SimplifyCFG.cpp b/llvm/lib/Transforms/Utils/SimplifyCFG.cpp index ab1a474db9a..79d4857c2c8 100644 --- a/llvm/lib/Transforms/Utils/SimplifyCFG.cpp +++ b/llvm/lib/Transforms/Utils/SimplifyCFG.cpp @@ -2425,7 +2425,12 @@ static bool FoldTwoEntryPHINode(PHINode *PN, const TargetTransformInfo &TTI, if (IfBlock2) hoistAllInstructionsInto(DomBlock, InsertPt, IfBlock2); + // Propagate fast-math-flags from phi nodes to replacement selects. + IRBuilder<>::FastMathFlagGuard FMFGuard(Builder); while (PHINode *PN = dyn_cast(BB->begin())) { + if (isa(PN)) + Builder.setFastMathFlags(PN->getFastMathFlags()); + // Change the PHI node into a select instruction. Value *TrueVal = PN->getIncomingValue(PN->getIncomingBlock(0) == IfFalse); Value *FalseVal = PN->getIncomingValue(PN->getIncomingBlock(0) == IfTrue); -- cgit v1.2.3