From cb8c009801c927c4f6401d76bac45370c936d778 Mon Sep 17 00:00:00 2001 From: Sanjay Patel Date: Sat, 16 Dec 2017 16:11:17 +0000 Subject: [Driver, CodeGen] pass through and apply -fassociative-math There are 2 parts to getting the -fassociative-math command-line flag translated to LLVM FMF: 1. In the driver/frontend, we accept the flag and its 'no' inverse and deal with the interactions with other flags like -ffast-math -fno-signed-zeros -fno-trapping-math. This was mostly already done - we just need to translate the flag as a codegen option. The test file is complicated because there are many potential combinations of flags here. Note that we are matching gcc's behavior that requires 'nsz' and no-trapping-math. 2. In codegen, we map the codegen option to FMF in the IR builder. This is simple code and corresponding test. For the motivating example from PR27372: float foo(float a, float x) { return ((a + x) - x); } $ ./clang -O2 27372.c -S -o - -ffast-math -fno-associative-math -emit-llvm | egrep 'fadd|fsub' %add = fadd nnan ninf nsz arcp contract float %0, %1 %sub = fsub nnan ninf nsz arcp contract float %add, %2 So 'reassoc' is off as expected (and so is the new 'afn' but that's a different patch). This case now works as expected end-to-end although the underlying logic is still wrong: $ ./clang -O2 27372.c -S -o - -ffast-math -fno-associative-math | grep xmm addss %xmm1, %xmm0 subss %xmm1, %xmm0 We're not done because the case where 'reassoc' is set is ignored by optimizer passes. Example: $ ./clang -O2 27372.c -S -o - -fassociative-math -fno-signed-zeros -fno-trapping-math -emit-llvm | grep fadd %add = fadd reassoc float %0, %1 $ ./clang -O2 27372.c -S -o - -fassociative-math -fno-signed-zeros -fno-trapping-math | grep xmm addss %xmm1, %xmm0 subss %xmm1, %xmm0 Differential Revision: https://reviews.llvm.org/D39812 llvm-svn: 320920 --- clang/lib/Frontend/CompilerInvocation.cpp | 1 + 1 file changed, 1 insertion(+) (limited to 'clang/lib/Frontend/CompilerInvocation.cpp') diff --git a/clang/lib/Frontend/CompilerInvocation.cpp b/clang/lib/Frontend/CompilerInvocation.cpp index 9fabcdf05a8..2e8a737de4e 100644 --- a/clang/lib/Frontend/CompilerInvocation.cpp +++ b/clang/lib/Frontend/CompilerInvocation.cpp @@ -639,6 +639,7 @@ static bool ParseCodeGenArgs(CodeGenOptions &Opts, ArgList &Args, InputKind IK, Args.hasArg(OPT_cl_no_signed_zeros) || Args.hasArg(OPT_cl_unsafe_math_optimizations) || Args.hasArg(OPT_cl_fast_relaxed_math)); + Opts.Reassociate = Args.hasArg(OPT_mreassociate); Opts.FlushDenorm = Args.hasArg(OPT_cl_denorms_are_zero); Opts.CorrectlyRoundedDivSqrt = Args.hasArg(OPT_cl_fp32_correctly_rounded_divide_sqrt); -- cgit v1.2.3