[PATCH] D72675: ix -ffast-math/-ffp-contract interaction

[Warren Ristow via Phabricator via cfe-commits]

wristow created this revision.
wristow added reviewers: spatel, mcberg2017.
Herald added subscribers: jsji, hiraditya, nemanjai.
Herald added a project: LLVM.

Fused Multiply Add (FMA) was not always being disabled when the switch `-ffp-contract=off` was used.  More specifically, FMA is enabled when `-ffp-contract=fast` is used, and it also is enabled implicitly with `-ffast-math`.  The combination:

  -ffast-math -ffp-contract=off

is intended to leave most of fast-math enabled (for example, leave reassociation, reciprocal transformations, etc.) enabled, but disable the use of FMA.  However, FMA was incorrectly left enabled with the above switch combination.  This commit fixes this, allowing users to enable most of the fast-math optimizations, while disabling the FMA feature.


https://reviews.llvm.org/D72675

Files:
  clang/lib/Driver/ToolChains/Clang.cpp
  clang/test/Driver/fast-math.c
  llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
  llvm/test/CodeGen/PowerPC/fmf-propagation.ll
  llvm/test/CodeGen/X86/fp-contract.ll

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