[PATCH] D140858: [InstCombine]: Don't simplify bits if it causes imm32 to become imm64

[Noah Goldstein via Phabricator via llvm-commits]

goldstein.w.n added inline comments.


================
Comment at: llvm/lib/Transforms/InstCombine/InstCombineSimplifyDemanded.cpp:68
+      return false;
+  }
+
----------------
goldstein.w.n wrote:
> lebedev.ri wrote:
> > I think we are missing an inverse case.
> > If we have some large number, and we don't demand it's sign bits,
> > and if setting them allows it to become smaller, we should probably do that.
> > I think we are missing an inverse case.
> > If we have some large number, and we don't demand it's sign bits,
> > and if setting them allows it to become smaller, we should probably do that.
> 
> Good catch will check that out in V3.
> I think we are missing an inverse case.
> If we have some large number, and we don't demand it's sign bits,
> and if setting them allows it to become smaller, we should probably do that.

I implemented this but saw zero cases where it could apply.
it made the code more complex so would prefer to skip it in this patch at the very least.
That okay?


Repository:
  rG LLVM Github Monorepo

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  https://reviews.llvm.org/D140858/new/

https://reviews.llvm.org/D140858