[llvm-dev] [FPEnv] FNEG instruction

[Cameron McInally via llvm-dev]

On Wed, Sep 26, 2018 at 2:14 PM Kevin Neal via llvm-dev <
llvm-dev at lists.llvm.org> wrote:

> Do we really want to have fneg be the only instruction with guaranteed no
> side effects? That just sounds like a gotcha waiting to happen. Or it could
> result in horrible code depending on the architecture.
>

That's not quite right. FNEG(X) and FSUB(-0.0, X) are not the same
operation. They are *very* similar, but still different at an edge case(s).
The current transformations that occur in LLVM are unsafe.
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