[PATCH] D23134: Make cltz and cttz zero undef when the operand cannot be zero in InstCombine

[Amaury SECHET via llvm-commits]

deadalnix added inline comments.

================
Comment at: lib/Transforms/InstCombine/InstCombineCalls.cpp:1141
@@ +1140,3 @@
+    if (!match(II.getArgOperand(1), m_One())) {
+      IC.Worklist.Add(&II);
+      II.setOperand(1, IC.Builder->getTrue());
----------------
spatel wrote:
> Shouldn't this return the updated instruction to signal to the callers that a change was made? If we do that, then we don't need to explicitly add to the worklist either, right?
No as we don't want to go though replacing the instruction by itself and we especially don't want to replace false by true in the program.


https://reviews.llvm.org/D23134