[PATCH] D61419: Support FNeg constant folding

[Matt Arsenault via Phabricator via llvm-commits]

arsenm added inline comments.


================
Comment at: llvm/test/CodeGen/X86/fp-fold.ll:226-242
+
+define float @fneg_undef() {
+; ANY-LABEL: fneg_undef:
+; ANY:       # %bb.0:
+; ANY-NEXT:    retq
+  %r = fneg float undef
+  ret float %r
----------------
cameron.mcinally wrote:
> arsenm wrote:
> > cameron.mcinally wrote:
> > > arsenm wrote:
> > > > These tests don't really belong in codegen (same for the vector cases).
> > > > 
> > > > Can you also add a test with some weird constant expressions as a source?
> > > > These tests don't really belong in codegen (same for the vector cases).
> > > 
> > > I'm not that familiar with LLVM's testing layout. Where should they go?
> > > 
> > > > Can you also add a test with some weird constant expressions as a source?
> > > 
> > > Do you mean like the `42.0` I see everywhere? Or something more exotic?
> > > 
> > > There are existing tests that exercise NaN, Inf, and undef in place now. Those came for free from the old `FNEG(X)` -> `FSUB(-0.0, X)` work.
> > Looks like test/Analysis/ConstantFolding is probably the right place.
> > 
> > I mean something like a bitcast of a global address, that isa<Constant>, but isn't ConstantFP
> Sorry, my ignorance is showing here...
> 
> > Looks like test/Analysis/ConstantFolding is probably the right place.
> 
> It looks like all the `RUN:` lines in that directory invoke `opt` with a specific pass or general optimization level. I think I need `llc` to trigger the constant folder for this patch. Is that correct? Or am I missing something obvious...
llc should definitely not be needed.

I would expect -instsimplify to work.


Repository:
  rL LLVM

CHANGES SINCE LAST ACTION
  https://reviews.llvm.org/D61419/new/

https://reviews.llvm.org/D61419