teach ConstantRange that zero times X is always zero
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@160317 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/Support/ConstantRange.cpp b/lib/Support/ConstantRange.cpp
index b83dccc..221ca94 100644
--- a/lib/Support/ConstantRange.cpp
+++ b/lib/Support/ConstantRange.cpp
@@ -537,6 +537,12 @@
if (isEmptySet() || Other.isEmptySet())
return ConstantRange(getBitWidth(), /*isFullSet=*/false);
+
+ // If any of the operands is zero, then the result is also zero.
+ if ((getSingleElement() && *getSingleElement() == 0) ||
+ (Other.getSingleElement() && *Other.getSingleElement() == 0))
+ return ConstantRange(APInt(getBitWidth(), 0));
+
if (isFullSet() || Other.isFullSet())
return ConstantRange(getBitWidth(), /*isFullSet=*/true);