[ConstantRange] Add unsignedMulMayOverflow()

[nikic]

Summary

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

[lebedev.ri]

LG modulo all the typos..

llvm/unittests/IR/ConstantRangeTest.cpp

1581

Uhm, i should have noticed this sooner, but then i make typos all the time.
Here and *everywhere*, s/Exhautive/Exhaustive/.

[nikic]

llvm/unittests/IR/ConstantRangeTest.cpp

1581

Gah, I keep making this typo... Fixed in rL358227.

llvm/include/llvm/IR/ConstantRange.h

public:
   OverflowResult signedAddMayOverflow(const ConstantRange &Other) const;
 
   /// Return whether unsigned sub of the two ranges always/never overflows.
   OverflowResult unsignedSubMayOverflow(const ConstantRange &Other) const;
 
   /// Return whether signed sub of the two ranges always/never overflows.
   OverflowResult signedSubMayOverflow(const ConstantRange &Other) const;
 
+  /// Return whether unsigned mul of the two ranges always/never overflows.
+  OverflowResult unsignedMulMayOverflow(const ConstantRange &Other) const;
+
   /// Print out the bounds to a stream.
   void print(raw_ostream &OS) const;
 
   /// Allow printing from a debugger easily.
   void dump() const;
 };
 
 inline raw_ostream &operator<<(raw_ostream &OS, const ConstantRange &CR) {

llvm/lib/IR/ConstantRange.cpp

if (Max.isNonNegative() && OtherMin.isNegative() &&
     return OverflowResult::MayOverflow;
   if (Min.isNegative() && OtherMax.isNonNegative() &&
       Min.slt(SignedMin + OtherMax))
     return OverflowResult::MayOverflow;
 
   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";
   else if (isEmptySet())
     OS << "empty-set";
   else
     OS << "[" << Lower << "," << Upper << ")";
 }

llvm/unittests/IR/ConstantRangeTest.cpp

TestOverflowExhaustive(
         (void) N1.usub_ov(N2, Overflow);
         return Overflow;
       },
       [](const ConstantRange &CR1, const ConstantRange &CR2) {
         return CR1.unsignedSubMayOverflow(CR2);
       });
 }
 
+TEST_F(ConstantRangeTest, UnsignedMulOverflowExhautive) {
+  TestOverflowExhaustive(
+      [](const APInt &N1, const APInt &N2) {
+        bool Overflow;
+        (void) N1.umul_ov(N2, Overflow);
+        return Overflow;
+      },
+      [](const ConstantRange &CR1, const ConstantRange &CR2) {
+        return CR1.unsignedMulMayOverflow(CR2);
+      });
+}
+
 TEST_F(ConstantRangeTest, SignedAddOverflowExhautive) {
   TestOverflowExhaustive(
       [](const APInt &N1, const APInt &N2) {
         bool Overflow;
         (void) N1.sadd_ov(N2, Overflow);
         return Overflow;
       },
       [](const ConstantRange &CR1, const ConstantRange &CR2) {