fixup! [ConstantRange] Improve ConstantRange::binaryXor

Address review comments.

Author: dtcxzyw

llvm/lib/IR/ConstantRange.cpp

@@ -1478,16 +1478,10 @@ ConstantRange ConstantRange::binaryXor(const ConstantRange &Other) const {
   // If LHS is known to be the subset of RHS, treat LHS ^ RHS as RHS -nuw/nsw
   // LHS. If RHS is known to be the subset of LHS, treat LHS ^ RHS as LHS
   // -nuw/nsw RHS.
-  if (LHSKnown.getMaxValue().isSubsetOf(RHSKnown.getMinValue()))
-    CR = CR.intersectWith(
-        Other.subWithNoWrap(*this, OverflowingBinaryOperator::NoUnsignedWrap |
-                                       OverflowingBinaryOperator::NoSignedWrap),
-        PreferredRangeType::Unsigned);
-  else if (RHSKnown.getMaxValue().isSubsetOf(LHSKnown.getMinValue()))
-    CR = CR.intersectWith(
-        subWithNoWrap(Other, OverflowingBinaryOperator::NoUnsignedWrap |
-                                 OverflowingBinaryOperator::NoSignedWrap),
-        PreferredRangeType::Unsigned);
+  if ((~LHSKnown.Zero).isSubsetOf(RHSKnown.One))
+    CR = CR.intersectWith(Other.sub(*this), PreferredRangeType::Unsigned);
+  else if ((~RHSKnown.Zero).isSubsetOf(LHSKnown.One))
+    CR = CR.intersectWith(this->sub(Other), PreferredRangeType::Unsigned);
   return CR;
 }
 

llvm/unittests/IR/ConstantRangeTest.cpp

@@ -2565,6 +2565,12 @@ TEST_F(ConstantRangeTest, binaryXor) {
   EXPECT_EQ(R16_35.binaryXor(R0_99), ConstantRange(APInt(8, 0), APInt(8, 128)));
   EXPECT_EQ(R0_99.binaryXor(R16_35), ConstantRange(APInt(8, 0), APInt(8, 128)));
 
+  // Treat xor A, B as sub nsw nuw A, B
+  ConstantRange R0_51(APInt(8, 0), APInt(8, 51));
+  ConstantRange R63(APInt(8, 63));
+  EXPECT_EQ(R0_51.binaryXor(R63), ConstantRange(APInt(8, 13), APInt(8, 64)));
+  EXPECT_EQ(R63.binaryXor(R0_51), ConstantRange(APInt(8, 13), APInt(8, 64)));
+
   TestBinaryOpExhaustive(
       [](const ConstantRange &CR1, const ConstantRange &CR2) {
         return CR1.binaryXor(CR2);