[PATCH] D155461: [InstCombine] Keep !unpredictable when combining select+add

Wed Jul 19 03:05:12 PDT 2023

chfast added inline comments.

================
Comment at: llvm/lib/Transforms/InstCombine/InstCombineSelect.cpp:540
       Value *NewSel = Builder.CreateSelect(SI.getCondition(), Swapped ? C : OOp,
-                                           Swapped ? OOp : C);
+                                           Swapped ? OOp : C, "", &SI);
       if (isa<FPMathOperator>(&SI))
----------------
goldstein.w.n wrote:
> chfast wrote:
> > goldstein.w.n wrote:
> > > chfast wrote:
> > > > I believe there are more case in the file where metadata copy is missed. I will try to identify them and create more tests cases. Can be in this review on later, depending on reviewers' suggestion.
> > > Are there any other binops you want to preserve this flag for?
> > I think it make sense for any binop because the condition of the select in this transformation remains unchanged (i.e. `!unpredictable` is still applicable).
> I think you have this in the right place for most binops, but you should probably add additional tests for things like:
> `sub`, `or`, `xor`, `and`, `mul`, `div`, `rem`, `llvm.min`, `llvm.max`, etc...
> 
> you probably don't need all but some variety of those (like 1/2 bitwise, div or rem, a few intrinsics) should provide better coverage.
I added tests for most instructions from `getSelectFoldableOperands`. There are no any intrinsics there.

Repository:
  rG LLVM Github Monorepo

CHANGES SINCE LAST ACTION
  https://reviews.llvm.org/D155461/new/

https://reviews.llvm.org/D155461