[PATCH] D126364: Fix interaction of pragma FENV_ACCESS with other pragmas

Mon Jun 6 11:56:37 PDT 2022

sepavloff added inline comments.

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Comment at: clang/include/clang/Basic/LangOptions.h:622
     setFPContractMode(LangOptions::FPM_Off);
     setRoundingMode(static_cast<RoundingMode>(LangOptions::FPR_ToNearest));
     setFPExceptionMode(LangOptions::FPE_Ignore);
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efriedma wrote:
> I'm suggesting this should be `setRoundingMode(llvm::RoundingMode::Dynamic)`.
> 
> If FENV_ACCESS is off, getEffectiveRoundingMode() converts that to "nearest".  If FENV_ACCESS is turned on, the mode is treated as dynamic.  This is exactly what we want.
It would change semantics. In particular, it would make impossible to use FP arithmetic in constexpr functions. An expression like `1.0 / 3.0` cannot be evaluated with dynamic rounding mode.

Repository:
  rG LLVM Github Monorepo

CHANGES SINCE LAST ACTION
  https://reviews.llvm.org/D126364/new/

https://reviews.llvm.org/D126364