[PATCH] D50913: [FPEnv] Don't need copysign/fabs/fneg constrained intrinsics

[Ulrich Weigand via Phabricator via llvm-commits]

uweigand added a comment.

I believe we still don't need an intrinsic for constrained fneg.   As you say, floating-point negation is implemented as -0-x, using a regular fsub (*not* the constrained intrinsic).   The fsub semantics says that it cannot trap, so this would still be fine -- as long as we're sure the -0-x is always implemented via a dedicated negate instruction, and never via a subtraction.  But this seems to be true, the idiom -0-x is recognized early during codegen and always treated specially.


Repository:
  rL LLVM

https://reviews.llvm.org/D50913