[PATCH] D28405: SimplifyLibCalls: Replace fabs libcalls with intrinsics

Matt Arsenault via Phabricator via llvm-commits llvm-commits at lists.llvm.org
Mon Jan 16 13:45:06 PST 2017

arsenm added inline comments.

Comment at: test/Transforms/InstCombine/fabs.ll:16
 ; CHECK-NEXT: %mul = fmul float %x, %x
-; CHECK-NEXT: %fabsf = tail call float @fabsf(float %mul)
+; CHECK-NEXT: %fabsf = call float @llvm.fabs.f32(float %mul)
 ; CHECK-NEXT: ret float %fabsf
efriedma wrote:
> arsenm wrote:
> > arsenm wrote:
> > > efriedma wrote:
> > > > efriedma wrote:
> > > > > This is probably going to fail on Windows... maybe change the test to call llvm.fabs rather than fabs?
> > > > Still probably going to fail on Windows, where fabsf() doesn't exist.
> > > Do you mean the intrinsic won't work? I would expect codegen to promote it
> > It looks like a fabs instruction is emitted for the intrinsic
> No... I mean we call `TLI.setUnavailable(LibFunc::fabsf);` on Windows, so it isn't a library call, so we'll never call optimizeFabs.
I thought the intent there was to not recognize fabsf as a special builtin function since it isn't available, i.e. fabsf could be a user function


More information about the llvm-commits mailing list