[PATCH] D43565: [SimplifyCFG] Expanding scope for hoisting common instructions after branch

[Eli Friedman via Phabricator via llvm-commits]

efriedma added a comment.

LLVM has a GVNHoist pass, which is both more efficient and more effective than anything we can do in SimplifyCFG.  (It's currently off by default, but it could probably be turned on with a bit more testing/bugfixing.)  I would rather focus on getting that turned on, instead of doing something like this.



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Comment at: lib/Transforms/Utils/SimplifyCFG.cpp:1275
+  for (unsigned Count1 = 0;
+       TmpItr1 != BB1->end() && Count1 < SCAN_LIMIT; Count1++) {
+    Instruction *TmpI1 = &*TmpItr1++;
----------------
The way you're counting instructions here is wrong: you have to skip debug info.

It looks like this can only hoist one instruction each time HoistThenElseCodeToIf is called?


https://reviews.llvm.org/D43565