InstCombine: Fix a crash in Descale for multiply-by-zero
Fix a crash in `InstCombiner::Descale()` when a multiply-by-zero gets
created as an argument to a GEP partway through an iteration, causing
-instcombine to optimize the GEP before the multiply.
rdar://problem/17615671
llvm-svn: 212742
diff --git a/llvm/lib/Transforms/InstCombine/InstructionCombining.cpp b/llvm/lib/Transforms/InstCombine/InstructionCombining.cpp
index 46e3bfc..08e2446 100644
--- a/llvm/lib/Transforms/InstCombine/InstructionCombining.cpp
+++ b/llvm/lib/Transforms/InstCombine/InstructionCombining.cpp
@@ -1120,6 +1120,12 @@
return nullptr;
}
+ // If Op is zero then Val = Op * Scale.
+ if (match(Op, m_Zero())) {
+ NoSignedWrap = true;
+ return Op;
+ }
+
// We know that we can successfully descale, so from here on we can safely
// modify the IR. Op holds the descaled version of the deepest term in the
// expression. NoSignedWrap is 'true' if multiplying Op by Scale is known