[PATCH] D149786: [SCEV] Try smaller ZExts when using loop guard info.

Florian Hahn via Phabricator via llvm-commits llvm-commits at lists.llvm.org
Fri May 5 02:08:33 PDT 2023


fhahn marked an inline comment as done.
fhahn added inline comments.


================
Comment at: llvm/lib/Analysis/ScalarEvolution.cpp:14941
+            return SE.getZeroExtendExpr(I->second, Ty);
+          Bitwidth = Bitwidth / 2;
+        }
----------------
mkazantsev wrote:
> If `Bitwidth` is `8 * 9 = 72`, at some point you will end up with `BitWidth = 9` and enter this loop, and then on division you will lose a meaningful last bit. Was it your intention?
> 
> I think `Bitwidth % 8 == 0` thingy should be in `while` loop.
Thanks, updated!


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