5 files changed, 82 insertions, 21 deletions
diff --git a/llvm/include/llvm/ADT/APInt.h b/llvm/include/llvm/ADT/APInt.h
index 1abea9e..b9b39f3 100644
--- a/llvm/include/llvm/ADT/APInt.h
+++ b/llvm/include/llvm/ADT/APInt.h
@@ -2216,6 +2216,14 @@ APInt avgCeilS(const APInt &C1, const APInt &C2);
 /// Compute the ceil of the unsigned average of C1 and C2
 APInt avgCeilU(const APInt &C1, const APInt &C2);
 
+/// Performs (2*N)-bit multiplication on sign-extended operands.
+/// Returns the high N bits of the multiplication result.
+APInt mulhs(const APInt &C1, const APInt &C2);
+
+/// Performs (2*N)-bit multiplication on zero-extended operands.
+/// Returns the high N bits of the multiplication result.
+APInt mulhu(const APInt &C1, const APInt &C2);
+
 /// Compute GCD of two unsigned APInt values.
 ///
 /// This function returns the greatest common divisor of the two APInt values
diff --git a/llvm/lib/CodeGen/SelectionDAG/SelectionDAG.cpp b/llvm/lib/CodeGen/SelectionDAG/SelectionDAG.cpp
index e3b76b9..8c543ae 100644
--- a/llvm/lib/CodeGen/SelectionDAG/SelectionDAG.cpp
+++ b/llvm/lib/CodeGen/SelectionDAG/SelectionDAG.cpp
@@ -6078,18 +6078,6 @@ static std::optional<APInt> FoldValue(unsigned Opcode, const APInt &C1,
     if (!C2.getBoolValue())
       break;
     return C1.srem(C2);
-  case ISD::MULHS: {
-    unsigned FullWidth = C1.getBitWidth() * 2;
-    APInt C1Ext = C1.sext(FullWidth);
-    APInt C2Ext = C2.sext(FullWidth);
-    return (C1Ext * C2Ext).extractBits(C1.getBitWidth(), C1.getBitWidth());
-  }
-  case ISD::MULHU: {
-    unsigned FullWidth = C1.getBitWidth() * 2;
-    APInt C1Ext = C1.zext(FullWidth);
-    APInt C2Ext = C2.zext(FullWidth);
-    return (C1Ext * C2Ext).extractBits(C1.getBitWidth(), C1.getBitWidth());
-  }
   case ISD::AVGFLOORS:
     return APIntOps::avgFloorS(C1, C2);
   case ISD::AVGFLOORU:
@@ -6102,10 +6090,13 @@ static std::optional<APInt> FoldValue(unsigned Opcode, const APInt &C1,
     return APIntOps::abds(C1, C2);
   case ISD::ABDU:
     return APIntOps::abdu(C1, C2);
+  case ISD::MULHS:
+    return APIntOps::mulhs(C1, C2);
+  case ISD::MULHU:
+    return APIntOps::mulhu(C1, C2);
   }
   return std::nullopt;
 }
-
 // Handle constant folding with UNDEF.
 // TODO: Handle more cases.
 static std::optional<APInt> FoldValueWithUndef(unsigned Opcode, const APInt &C1,
diff --git a/llvm/lib/Support/APInt.cpp b/llvm/lib/Support/APInt.cpp
index 7a383c3..c206097 100644
--- a/llvm/lib/Support/APInt.cpp
+++ b/llvm/lib/Support/APInt.cpp
@@ -3121,3 +3121,19 @@ APInt APIntOps::avgCeilU(const APInt &C1, const APInt &C2) {
   // Return ceil((C1 + C2) / 2)
   return (C1 | C2) - (C1 ^ C2).lshr(1);
 }
+
+APInt APIntOps::mulhs(const APInt &C1, const APInt &C2) {
+  assert(C1.getBitWidth() == C2.getBitWidth() && "Unequal bitwidths");
+  unsigned FullWidth = C1.getBitWidth() * 2;
+  APInt C1Ext = C1.sext(FullWidth);
+  APInt C2Ext = C2.sext(FullWidth);
+  return (C1Ext * C2Ext).extractBits(C1.getBitWidth(), C1.getBitWidth());
+}
+
+APInt APIntOps::mulhu(const APInt &C1, const APInt &C2) {
+  assert(C1.getBitWidth() == C2.getBitWidth() && "Unequal bitwidths");
+  unsigned FullWidth = C1.getBitWidth() * 2;
+  APInt C1Ext = C1.zext(FullWidth);
+  APInt C2Ext = C2.zext(FullWidth);
+  return (C1Ext * C2Ext).extractBits(C1.getBitWidth(), C1.getBitWidth());
+}
diff --git a/llvm/unittests/ADT/APIntTest.cpp b/llvm/unittests/ADT/APIntTest.cpp
index 83cbb02..d5ef63e 100644
--- a/llvm/unittests/ADT/APIntTest.cpp
+++ b/llvm/unittests/ADT/APIntTest.cpp
@@ -2841,6 +2841,58 @@ TEST(APIntTest, multiply) {
   EXPECT_EQ(64U, i96.countr_zero());
 }
 
+TEST(APIntOpsTest, Mulh) {
+
+  // Unsigned
+
+  // 32 bits
+  APInt i32a(32, 0x0001'E235);
+  APInt i32b(32, 0xF623'55AD);
+  EXPECT_EQ(0x0001'CFA1, APIntOps::mulhu(i32a, i32b));
+
+  // 64 bits
+  APInt i64a(64, 0x1234'5678'90AB'CDEF);
+  APInt i64b(64, 0xFEDC'BA09'8765'4321);
+  EXPECT_EQ(0x121F'A000'A372'3A57, APIntOps::mulhu(i64a, i64b));
+
+  // 128 bits
+  APInt i128a(128, "1234567890ABCDEF1234567890ABCDEF", 16);
+  APInt i128b(128, "FEDCBA0987654321FEDCBA0987654321", 16);
+  APInt i128Res = APIntOps::mulhu(i128a, i128b);
+  EXPECT_EQ(APInt(128, "121FA000A3723A57E68984312C3A8D7E", 16), i128Res);
+
+  // Signed
+
+  // 32 bits
+  APInt i32c(32, 0x1234'5678); // +ve
+  APInt i32d(32, 0x10AB'CDEF); // +ve
+  APInt i32e(32, 0xFEDC'BA09); // -ve
+
+  EXPECT_EQ(0x012F'7D02, APIntOps::mulhs(i32c, i32d));
+  EXPECT_EQ(0xFFEB'4988, APIntOps::mulhs(i32c, i32e));
+  EXPECT_EQ(0x0001'4B68, APIntOps::mulhs(i32e, i32e));
+
+  // 64 bits
+  APInt i64c(64, 0x1234'5678'90AB'CDEF); // +ve
+  APInt i64d(64, 0x1234'5678'90FE'DCBA); // +ve
+  APInt i64e(64, 0xFEDC'BA09'8765'4321); // -ve
+
+  EXPECT_EQ(0x014B'66DC'328E'10C1, APIntOps::mulhs(i64c, i64d));
+  EXPECT_EQ(0xFFEB'4988'12C6'6C68, APIntOps::mulhs(i64c, i64e));
+  EXPECT_EQ(0x0001'4B68'2174'FA18, APIntOps::mulhs(i64e, i64e));
+
+  // 128 bits
+  APInt i128c(128, "1234567890ABCDEF1234567890ABCDEF", 16); // +ve
+  APInt i128d(128, "1234567890FEDCBA1234567890FEDCBA", 16); // +ve
+  APInt i128e(128, "FEDCBA0987654321FEDCBA0987654321", 16); // -ve
+
+  i128Res = APIntOps::mulhs(i128c, i128d);
+  EXPECT_EQ(APInt(128, "14B66DC328E10C1FE303DF9EA0B2529", 16), i128Res);
+
+  i128Res = APIntOps::mulhs(i128c, i128e);
+  EXPECT_EQ(APInt(128, "FFEB498812C66C68D4552DB89B8EBF8F", 16), i128Res);
+}
+
 TEST(APIntTest, RoundingUDiv) {
   for (uint64_t Ai = 1; Ai <= 255; Ai++) {
     APInt A(8, Ai);
diff --git a/llvm/unittests/Support/KnownBitsTest.cpp b/llvm/unittests/Support/KnownBitsTest.cpp
index 48de088..027d637 100644
--- a/llvm/unittests/Support/KnownBitsTest.cpp
+++ b/llvm/unittests/Support/KnownBitsTest.cpp
@@ -553,17 +553,11 @@ TEST(KnownBitsTest, BinaryExhaustive) {
       checkCorrectnessOnlyBinary);
   testBinaryOpExhaustive(
       KnownBits::mulhs,
-      [](const APInt &N1, const APInt &N2) {
-        unsigned Bits = N1.getBitWidth();
-        return (N1.sext(2 * Bits) * N2.sext(2 * Bits)).extractBits(Bits, Bits);
-      },
+      [](const APInt &N1, const APInt &N2) { return APIntOps::mulhs(N1, N2); },
       checkCorrectnessOnlyBinary);
   testBinaryOpExhaustive(
       KnownBits::mulhu,
-      [](const APInt &N1, const APInt &N2) {
-        unsigned Bits = N1.getBitWidth();
-        return (N1.zext(2 * Bits) * N2.zext(2 * Bits)).extractBits(Bits, Bits);
-      },
+      [](const APInt &N1, const APInt &N2) { return APIntOps::mulhu(N1, N2); },
       checkCorrectnessOnlyBinary);
 }