getSmallConstantTripMultiple should never return zero.
When the trip count is -1, getSmallConstantTripMultiple could return zero,
and this would cause runtime loop unrolling to assert. Instead of returning
zero, one is now returned (consistent with the existing overflow cases).
Fixes PR14167.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@166612 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/Analysis/ScalarEvolution.cpp b/lib/Analysis/ScalarEvolution.cpp
index 3e06298..148912b 100644
--- a/lib/Analysis/ScalarEvolution.cpp
+++ b/lib/Analysis/ScalarEvolution.cpp
@@ -3979,8 +3979,11 @@
ConstantInt *Result = MulC->getValue();
- // Guard against huge trip counts.
- if (!Result || Result->getValue().getActiveBits() > 32)
+ // Guard against huge trip counts (this requires checking
+ // for zero to handle the case where the trip count == -1 and the
+ // addition wraps).
+ if (!Result || Result->getValue().getActiveBits() > 32 ||
+ Result->getValue().getActiveBits() == 0)
return 1;
return (unsigned)Result->getZExtValue();