[ConstantRange] Implement binaryXor() using known bits

This allows us to compute known high bits. It's not optimal, but
better than nothing.

diff --git a/llvm/lib/IR/ConstantRange.cpp b/llvm/lib/IR/ConstantRange.cpp
index 16eb4d0..ce2e537 100644 (file)
--- a/llvm/lib/IR/ConstantRange.cpp
+++ b/llvm/lib/IR/ConstantRange.cpp
@@ -1430,8 +1430,7 @@ ConstantRange ConstantRange::binaryXor(const ConstantRange &Other) const {
   if (isSingleElement() && getSingleElement()->isAllOnes())
     return Other.binaryNot();
 
-  // TODO: replace this with something less conservative
-  return getFull();
+  return fromKnownBits(toKnownBits() ^ Other.toKnownBits(), /*IsSigned*/false);
 }
 
 ConstantRange

diff --git a/llvm/unittests/IR/ConstantRangeTest.cpp b/llvm/unittests/IR/ConstantRangeTest.cpp
index b230a21..02f8b46 100644 (file)
--- a/llvm/unittests/IR/ConstantRangeTest.cpp
+++ b/llvm/unittests/IR/ConstantRangeTest.cpp
@@ -2535,12 +2535,22 @@ TEST_F(ConstantRangeTest, binaryXor) {
   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.
+  // Ranges with more than a single element.
   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());
+  EXPECT_EQ(R16_35.binaryXor(R16_35), ConstantRange(APInt(8, 0), APInt(8, 64)));
+  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)));
+
+  TestBinaryOpExhaustive(
+      [](const ConstantRange &CR1, const ConstantRange &CR2) {
+        return CR1.binaryXor(CR2);
+      },
+      [](const APInt &N1, const APInt &N2) {
+        return N1 ^ N2;
+      },
+      PreferSmallest,
+      CheckSingleElementsOnly);
 }
 
 TEST_F(ConstantRangeTest, binaryNot) {