[PATCH] D29777: [Reassociate] Convert shl by constant into multiply during tree linearization.

[Eli Friedman via Phabricator via llvm-commits]

efriedma added a comment.

I'm not following why this fixes the crash.  As far as I can tell, on trunk, Reassociate special-cases shl instructions in exactly one place: the check at the beginning of ReassociatePass::OptimizeInst.  In that case, we replace all the uses of the shl instruction, so it shouldn't matter.  (I'd like an answer to this to make sure you aren't papering over a real problem.)



================
Comment at: lib/Transforms/Scalar/Reassociate.cpp:371
+  Shl->replaceAllUsesWith(Mul);
+  Mul->setDebugLoc(Shl->getDebugLoc());
+
----------------
Why don't we don't erase the dead Shl here?


https://reviews.llvm.org/D29777