[PATCH] D80315: Fix CC1 command line options mapping into fast-math flags.

[Michele Scandale via Phabricator via cfe-commits]

michele.scandale requested review of this revision.
michele.scandale added a comment.

I've just realized it might be incorrect to have the CC1 option `-ffast-math` changing the default contraction mode. The clang driver generates `-ffast-math` based on conditions that do not involve the contraction mode state at all:

  // -ffast-math enables the __FAST_MATH__ preprocessor macro, but check for the
  // individual features enabled by -ffast-math instead of the option itself as
  // that's consistent with gcc's behaviour.
  if (!HonorINFs && !HonorNaNs && !MathErrno && AssociativeMath &&
      ReciprocalMath && !SignedZeros && !TrappingMath && !RoundingFPMath) {
    CmdArgs.push_back("-ffast-math");
    if (FPModel.equals("fast")) {
      if (FPContract.equals("fast"))
        // All set, do nothing.
        ;
      else if (FPContract.empty())
        // Enable -ffp-contract=fast
        CmdArgs.push_back(Args.MakeArgString("-ffp-contract=fast"));
      else
        D.Diag(clang::diag::warn_drv_overriding_flag_option)
          << "-ffp-model=fast"
          << Args.MakeArgString("-ffp-contract=" + FPContract);
    }
  }

For example the running the following `clang -### -funsafe-math-optimizations -ffinite-math-only -x c -` lead to a CC1 command line without any `-ffp-contract=` option relying on the fact that the default value for the contraction mode in the compiler is OFF.

I will revert the modification on this aspect.


Repository:
  rG LLVM Github Monorepo

CHANGES SINCE LAST ACTION
  https://reviews.llvm.org/D80315/new/

https://reviews.llvm.org/D80315