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[APInt] Extend isSameValue to also do signed-compares #178854

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Merged
artagnon merged 2 commits into from
Feb 1, 2026
Merged

[APInt] Extend isSameValue to also do signed-compares #178854

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e34f5d3
[APInt] Introduce isSameSignedValue
artagnon Jan 30, 2026
c66495a
[APInt] Fold isSameSignedValue into isSameValue
artagnon Jan 30, 2026
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12 changes: 12 additions & 0 deletions llvm/include/llvm/ADT/APInt.h
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Original file line number Diff line number Diff line change
Expand Up @@ -561,6 +561,18 @@ class [[nodiscard]] APInt {
return I1.zext(I2.getBitWidth()) == I2;
}

/// Determine if two APInts have the same value, after sign-extending
/// one of them (if needed!) to ensure that the bit-widths match.
static bool isSameSignedValue(const APInt &I1, const APInt &I2) {
if (I1.getBitWidth() == I2.getBitWidth())
return I1 == I2;

if (I1.getBitWidth() > I2.getBitWidth())
return I1 == I2.sext(I1.getBitWidth());

return I1.sext(I2.getBitWidth()) == I2;
}

/// Overload to compute a hash_code for an APInt value.
LLVM_ABI friend hash_code hash_value(const APInt &Arg);

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23 changes: 22 additions & 1 deletion llvm/unittests/ADT/APIntTest.cpp
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Expand Up @@ -14,7 +14,6 @@
#include "llvm/Support/Alignment.h"
#include "gtest/gtest.h"
#include <array>
#include <climits>
#include <limits>
#include <optional>

Expand All @@ -29,6 +28,28 @@ TEST(APIntTest, ValueInit) {
EXPECT_TRUE(!Zero.sext(64));
}

TEST(APIntTest, IsSameValueAndIsSameSignedValue) {
APInt One8(8, 1, /*isSigned=*/false);
APInt Three4(4, 3, /*isSigned=*/false);
EXPECT_FALSE(APInt::isSameValue(One8, Three4));
EXPECT_FALSE(APInt::isSameSignedValue(One8, Three4));

APInt Two8(8, 2, /*isSigned=*/false);
APInt Two4(4, 2, /*isSigned=*/false);
EXPECT_TRUE(APInt::isSameValue(Two8, Two4));
EXPECT_TRUE(APInt::isSameSignedValue(Two8, Two4));

APInt Seven8(8, 7, /*isSigned=*/false);
APInt Seven3(3, 7, /*isSigned=*/false);
EXPECT_TRUE(APInt::isSameValue(Seven8, Seven3));
EXPECT_FALSE(APInt::isSameSignedValue(Seven8, Seven3));

APInt Ones8 = APInt::getAllOnes(8);
APInt Ones4 = APInt::getAllOnes(4);
EXPECT_FALSE(APInt::isSameValue(Ones8, Ones4));
EXPECT_TRUE(APInt::isSameSignedValue(Ones8, Ones4));
}

// Test that 0^5 == 0
TEST(APIntTest, PowZeroTo5) {
APInt Zero = APInt::getZero(32);
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