[ConstantRange] Add initial support for binaryXor.

[fhahn]

Summary

The initial implementation just delegates to APInt's implementation of
XOR for single element ranges and conservatively returns the full set
otherwise.

[nikic]

LG

llvm/include/llvm/IR/ConstantRange.h

public:
   /// from a binary-and of a value in this range by a value in \p Other.
   ConstantRange binaryAnd(const ConstantRange &Other) const;
 
   /// Return a new range representing the possible values resulting
   /// from a binary-or of a value in this range by a value in \p Other.
   ConstantRange binaryOr(const ConstantRange &Other) const;
 
   /// Return a new range representing the possible values resulting
+  /// from a binary-xor of a value in this range by a value in \p Other.
+  ConstantRange binaryXor(const ConstantRange &Other) const;
+
+  /// Return a new range representing the possible values resulting
   /// from a left shift of a value in this range by a value in \p Other.
   /// TODO: This isn't fully implemented yet.
   ConstantRange shl(const ConstantRange &Other) const;
 
   /// Return a new range representing the possible values resulting from a
   /// logical right shift of a value in this range and a value in \p Other.
   ConstantRange lshr(const ConstantRange &Other) const;
 

llvm/lib/IR/ConstantRange.cpp

ConstantRange ConstantRange::binaryOp(Instruction::BinaryOps BinOp,
   case Instruction::LShr:
     return lshr(Other);
   case Instruction::AShr:
     return ashr(Other);
   case Instruction::And:
     return binaryAnd(Other);
   case Instruction::Or:
     return binaryOr(Other);
+  case Instruction::Xor:
+    return binaryXor(Other);
   // Note: floating point operations applied to abstract ranges are just
   // ideal integer operations with a lossy representation
   case Instruction::FAdd:
     return add(Other);
   case Instruction::FSub:
     return sub(Other);
   case Instruction::FMul:
     return multiply(Other);
if (isSingleElement() && Other.isSingleElement())
     return {*getSingleElement() | *Other.getSingleElement()};
 
   // TODO: replace this with something less conservative
 
   APInt umax = APIntOps::umax(getUnsignedMin(), Other.getUnsignedMin());
   return getNonEmpty(std::move(umax), APInt::getNullValue(getBitWidth()));
 }
 
+ConstantRange ConstantRange::binaryXor(const ConstantRange &Other) const {
+  if (isEmptySet() || Other.isEmptySet())
+    return getEmpty();
+
+  // Use APInt's implementation of XOR for single element ranges.
+  if (isSingleElement() && Other.isSingleElement())
+    return {*getSingleElement() ^ *Other.getSingleElement()};
+
+  // TODO: replace this with something less conservative
+  return getFull();
+}
+
 ConstantRange
 ConstantRange::shl(const ConstantRange &Other) const {
   if (isEmptySet() || Other.isEmptySet())
     return getEmpty();
 
   APInt max = getUnsignedMax();
   APInt Other_umax = Other.getUnsignedMax();
 

llvm/unittests/IR/ConstantRangeTest.cpp

TEST_F(ConstantRangeTest, castOps) {
   ConstantRange PtrToInt = A.castOp(Instruction::PtrToInt, 64);
   EXPECT_EQ(64u, PtrToInt.getBitWidth());
   EXPECT_TRUE(PtrToInt.isFullSet());
 
   ConstantRange IntToPtr = A.castOp(Instruction::IntToPtr, 64);
   EXPECT_EQ(64u, IntToPtr.getBitWidth());
   EXPECT_TRUE(IntToPtr.isFullSet());
 }
+
+TEST_F(ConstantRangeTest, binaryXor) {
+  // Single element ranges.
+  ConstantRange R16(APInt(8, 16));
+  ConstantRange R20(APInt(8, 20));
+  EXPECT_EQ(*R16.binaryXor(R16).getSingleElement(), APInt(8, 0));
+  EXPECT_EQ(*R16.binaryXor(R20).getSingleElement(), APInt(8, 16 ^ 20));
+
+  // Ranges with more than a single element. Handled conservatively for now.
+  ConstantRange R16_35(APInt(8, 16), APInt(8, 35));
+  ConstantRange R0_99(APInt(8, 0), APInt(8, 99));
+  EXPECT_TRUE(R16_35.binaryXor(R16_35).isFullSet());
+  EXPECT_TRUE(R16_35.binaryXor(R0_99).isFullSet());
+  EXPECT_TRUE(R0_99.binaryXor(R16_35).isFullSet());
+}
+
 }  // anonymous namespace