From ee0882bdf866ad8877dfda3820a822c851d0733a Mon Sep 17 00:00:00 2001 From: Sanjay Patel Date: Fri, 15 Nov 2019 16:06:43 -0500 Subject: [SimplifyCFG] propagate fast-math-flags (FMF) from phi to select 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 Differential Revision: https://reviews.llvm.org/D70208 --- llvm/lib/Transforms/Utils/SimplifyCFG.cpp | 8 +++++++- 1 file changed, 7 insertions(+), 1 deletion(-) (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 9644ba31f4d..ab1a474db9a 100644 --- a/llvm/lib/Transforms/Utils/SimplifyCFG.cpp +++ b/llvm/lib/Transforms/Utils/SimplifyCFG.cpp @@ -1404,10 +1404,16 @@ HoistTerminator: // These values do not agree. Insert a select instruction before NT // that determines the right value. SelectInst *&SI = InsertedSelects[std::make_pair(BB1V, BB2V)]; - if (!SI) + if (!SI) { + // Propagate fast-math-flags from phi node to its replacement select. + IRBuilder<>::FastMathFlagGuard FMFGuard(Builder); + if (isa(PN)) + Builder.setFastMathFlags(PN.getFastMathFlags()); + SI = cast( Builder.CreateSelect(BI->getCondition(), BB1V, BB2V, BB1V->getName() + "." + BB2V->getName(), BI)); + } // Make the PHI node use the select for all incoming values for BB1/BB2 for (unsigned i = 0, e = PN.getNumIncomingValues(); i != e; ++i) -- cgit v1.2.3