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

Mon Jun 6 12:05:10 PDT 2022

efriedma 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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sepavloff wrote:
> 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.
Can we just change the relevant code in ExprConstant to call getEffectiveRoundingMode()?

Repository:
  rG LLVM Github Monorepo

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

https://reviews.llvm.org/D126364