[llvm] a34bfac - [APInt] Extend isSameValue to also do signed-compares (#178854)

[via llvm-commits]

Author: Ramkumar Ramachandra
Date: 2026-02-01T11:32:36Z
New Revision: a34bfac6425eb83f8fba7c73b2a4bb31d1be4d98

URL: https://github.com/llvm/llvm-project/commit/a34bfac6425eb83f8fba7c73b2a4bb31d1be4d98
DIFF: https://github.com/llvm/llvm-project/commit/a34bfac6425eb83f8fba7c73b2a4bb31d1be4d98.diff

LOG: [APInt] Extend isSameValue to also do signed-compares (#178854)

Introduce a SignedCompare parameter of isSameValue to use sext instead
of zext.

Added: 
    

Modified: 
    llvm/include/llvm/ADT/APInt.h
    llvm/unittests/ADT/APIntTest.cpp

Removed: 
    


################################################################################
diff  --git a/llvm/include/llvm/ADT/APInt.h b/llvm/include/llvm/ADT/APInt.h
index 9193b5f8994e0..b6a659dde1b15 100644
--- a/llvm/include/llvm/ADT/APInt.h
+++ b/llvm/include/llvm/ADT/APInt.h
@@ -549,16 +549,22 @@ class [[nodiscard]] APInt {
   /// \returns the low "numBits" bits of this APInt.
   LLVM_ABI APInt getLoBits(unsigned numBits) const;
 
-  /// Determine if two APInts have the same value, after zero-extending
-  /// one of them (if needed!) to ensure that the bit-widths match.
-  static bool isSameValue(const APInt &I1, const APInt &I2) {
+  /// Determine if two APInts have the same value, after zero-extending or
+  /// sign-extending (if \p SignedCompare) one of them (if needed!) to ensure
+  /// that the bit-widths match.
+  static bool isSameValue(const APInt &I1, const APInt &I2,
+                          bool SignedCompare = false) {
     if (I1.getBitWidth() == I2.getBitWidth())
       return I1 == I2;
 
+    auto ZExtOrSExt = [SignedCompare](const APInt &I, unsigned BitWidth) {
+      return SignedCompare ? I.sext(BitWidth) : I.zext(BitWidth);
+    };
+
     if (I1.getBitWidth() > I2.getBitWidth())
-      return I1 == I2.zext(I1.getBitWidth());
+      return I1 == ZExtOrSExt(I2, I1.getBitWidth());
 
-    return I1.zext(I2.getBitWidth()) == I2;
+    return ZExtOrSExt(I1, I2.getBitWidth()) == I2;
   }
 
   /// Overload to compute a hash_code for an APInt value.

diff  --git a/llvm/unittests/ADT/APIntTest.cpp b/llvm/unittests/ADT/APIntTest.cpp
index 271d17cb29905..9bd283953f733 100644
--- a/llvm/unittests/ADT/APIntTest.cpp
+++ b/llvm/unittests/ADT/APIntTest.cpp
@@ -14,7 +14,6 @@
 #include "llvm/Support/Alignment.h"
 #include "gtest/gtest.h"
 #include <array>
-#include <climits>
 #include <limits>
 #include <optional>
 
@@ -29,6 +28,28 @@ TEST(APIntTest, ValueInit) {
   EXPECT_TRUE(!Zero.sext(64));
 }
 
+TEST(APIntTest, IsSameValue) {
+  APInt One8(8, 1, /*isSigned=*/false);
+  APInt Three4(4, 3, /*isSigned=*/false);
+  EXPECT_FALSE(APInt::isSameValue(One8, Three4, /*SignedCompare=*/false));
+  EXPECT_FALSE(APInt::isSameValue(One8, Three4, /*SignedCompare=*/true));
+
+  APInt Two8(8, 2, /*isSigned=*/false);
+  APInt Two4(4, 2, /*isSigned=*/false);
+  EXPECT_TRUE(APInt::isSameValue(Two8, Two4, /*SignedCompare=*/false));
+  EXPECT_TRUE(APInt::isSameValue(Two8, Two4, /*SignedCompare=*/true));
+
+  APInt Seven8(8, 7, /*isSigned=*/false);
+  APInt Seven3(3, 7, /*isSigned=*/false);
+  EXPECT_TRUE(APInt::isSameValue(Seven8, Seven3, /*SignedCompare=*/false));
+  EXPECT_FALSE(APInt::isSameValue(Seven8, Seven3, /*SignedCompare=*/true));
+
+  APInt Ones8 = APInt::getAllOnes(8);
+  APInt Ones4 = APInt::getAllOnes(4);
+  EXPECT_FALSE(APInt::isSameValue(Ones8, Ones4, /*SignedCompare=*/false));
+  EXPECT_TRUE(APInt::isSameValue(Ones8, Ones4, /*SignedCompare=*/true));
+}
+
 // Test that 0^5 == 0
 TEST(APIntTest, PowZeroTo5) {
   APInt Zero = APInt::getZero(32);