[PATCH] D83671: GlobalISel: Implement widenScalar for saturating add/sub

[Jay Foad via Phabricator via llvm-commits]

foad added inline comments.


================
Comment at: llvm/lib/CodeGen/GlobalISel/LegalizerHelper.cpp:1671
+
+  auto Result = IsSigned ? MIRBuilder.buildAShr(WideTy, WideInst, ShiftK)
+                         : MIRBuilder.buildLShr(WideTy, WideInst, ShiftK);
----------------
arsenm wrote:
> foad wrote:
> > There's no need to make this conditional on IsSigned if we're just about to truncate anyway.
> How else would I know whether to prefer ashr or lshr?
Why would it make any difference? Can't you just pick one arbitrarily?


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  https://reviews.llvm.org/D83671/new/

https://reviews.llvm.org/D83671