[PATCH] D104932: [instcombine] Fold overflow check using overflow intrinsic to comparison

[Sanjay Patel via Phabricator via llvm-commits]

spatel added inline comments.


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Comment at: llvm/test/Transforms/InstCombine/ssubo.ll:59
 
 define i1 @test_constant4(i8 %a) {
 ; CHECK-LABEL: @test_constant4(
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reames wrote:
> spatel wrote:
> > I focused in on this example, and we are missing a fold:
> > https://alive2.llvm.org/ce/z/EfBUXP
> > 
> > Does that hold for all of the overflow ops? Could we produce the optimal icmp directly (no add with constant necessary)?
> Hm, have to give this one some thought.  Would you mind if we did this incrementally?  i.e. land this, then improve?
I had to try to generalize this, and I think I have it:
https://alive2.llvm.org/ce/z/j4TDR_

I'll work on that patch now, so we don't have to worry about regressions for this set of tests at least (not sure if that is enough on its own for all tests).


Repository:
  rG LLVM Github Monorepo

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  https://reviews.llvm.org/D104932/new/

https://reviews.llvm.org/D104932