[PATCH] D85184: [Attributor][WIP] Deduce noundef attribute

[Shinji Okumura via Phabricator via llvm-commits]

okura added inline comments.


================
Comment at: llvm/lib/Transforms/IPO/AttributorAttributes.cpp:7178
+        case Instruction::SRem:
+          return true;
+        }
----------------
aqjune wrote:
> A value that is used as a divisor of div/rem can still have undef bits.
> ```
> a = undef | 1 ; a is not noundef because it has undef bits
> x = udiv 100, a ; this is not UB
> ```
> Can we use `isGuaranteedNotToBeUndefOrPoison` instead?
I was confusing the undef and poison value. Thanks for your example.
I will rewrite this part using `isGuaranteedNotToBeUndefOrPoison`.
I didn't know such a helpful function, thank you very much.


CHANGES SINCE LAST ACTION
  https://reviews.llvm.org/D85184/new/

https://reviews.llvm.org/D85184