[ConstantRange] Add unsignedMulMayOverflow()

Same as the other ConstantRange overflow checking methods, but for
unsigned mul. In this case there is no cheap overflow criterion, so
using umul_ov for the implementation.

Differential Revision: https://reviews.llvm.org/D60574

llvm-svn: 358228

1 files changed, 20 insertions, 0 deletions

diff --git a/llvm/lib/IR/ConstantRange.cpp b/llvm/lib/IR/ConstantRange.cpp
index 391d9653db5..35c2b0e2e2c 100644
--- a/llvm/lib/IR/ConstantRange.cpp
+++ b/llvm/lib/IR/ConstantRange.cpp
@@ -1252,6 +1252,26 @@ ConstantRange::OverflowResult ConstantRange::signedSubMayOverflow(
   return OverflowResult::NeverOverflows;
 }
 
+ConstantRange::OverflowResult ConstantRange::unsignedMulMayOverflow(
+    const ConstantRange &Other) const {
+  if (isEmptySet() || Other.isEmptySet())
+    return OverflowResult::MayOverflow;
+
+  APInt Min = getUnsignedMin(), Max = getUnsignedMax();
+  APInt OtherMin = Other.getUnsignedMin(), OtherMax = Other.getUnsignedMax();
+  bool Overflow;
+
+  (void) Min.umul_ov(OtherMin, Overflow);
+  if (Overflow)
+    return OverflowResult::AlwaysOverflows;
+
+  (void) Max.umul_ov(OtherMax, Overflow);
+  if (Overflow)
+    return OverflowResult::MayOverflow;
+
+  return OverflowResult::NeverOverflows;
+}
+
 void ConstantRange::print(raw_ostream &OS) const {
   if (isFullSet())
     OS << "full-set";