[Clang] VectorExprEvaluator::VisitCallExpr / InterpretBuiltin - allow MMX/SSE/AVX2 PSIGN intrinsics to be used in constexpr #163685

kimsh02 · 2025-10-16T02:47:25Z

Fix #155812

kimsh02 · 2025-10-17T22:11:10Z

@RKSimon 🙏

clang/lib/Headers/tmmintrin.h

llvmbot · 2025-10-20T16:53:58Z

@llvm/pr-subscribers-clang

@llvm/pr-subscribers-backend-x86

Author: Shawn K (kimsh02)

Changes

Fix #155812

Full diff: https://github.com/llvm/llvm-project/pull/163685.diff

8 Files Affected:

(modified) clang/include/clang/Basic/BuiltinsX86.td (+18-11)
(modified) clang/lib/AST/ByteCode/InterpBuiltin.cpp (+37)
(modified) clang/lib/AST/ExprConstant.cpp (+30)
(modified) clang/lib/Headers/avx2intrin.h (+9-12)
(modified) clang/lib/Headers/tmmintrin.h (+21-27)
(modified) clang/test/CodeGen/X86/avx2-builtins.c (+7)
(modified) clang/test/CodeGen/X86/mmx-builtins.c (+5)
(modified) clang/test/CodeGen/X86/ssse3-builtins.c (+3)

diff --git a/clang/include/clang/Basic/BuiltinsX86.td b/clang/include/clang/Basic/BuiltinsX86.td
index d03c778740ad3..825534436704c 100644
--- a/clang/include/clang/Basic/BuiltinsX86.td
+++ b/clang/include/clang/Basic/BuiltinsX86.td
@@ -123,13 +123,13 @@ let Attributes = [Const, NoThrow, RequiredVectorWidth<128>] in {
     }
   }
 
-  let Features = "ssse3" in {
-    def psignb128 : X86Builtin<"_Vector<16, char>(_Vector<16, char>, _Vector<16, char>)">;
-    def psignw128 : X86Builtin<"_Vector<8, short>(_Vector<8, short>, _Vector<8, short>)">;
-    def psignd128 : X86Builtin<"_Vector<4, int>(_Vector<4, int>, _Vector<4, int>)">;
-  }
-
   let Features = "ssse3", Attributes = [NoThrow, Const, Constexpr, RequiredVectorWidth<128>] in {
+    def psignb128
+        : X86Builtin<"_Vector<16, char>(_Vector<16, char>, _Vector<16, char>)">;
+    def psignw128
+        : X86Builtin<"_Vector<8, short>(_Vector<8, short>, _Vector<8, short>)">;
+    def psignd128
+        : X86Builtin<"_Vector<4, int>(_Vector<4, int>, _Vector<4, int>)">;
     def pmulhrsw128 : X86Builtin<"_Vector<8, short>(_Vector<8, short>, _Vector<8, short>)">;
     def pmaddubsw128 : X86Builtin<"_Vector<8, short>(_Vector<16, char>, _Vector<16, char>)">;
     def pshufb128 : X86Builtin<"_Vector<16, char>(_Vector<16, char>, _Vector<16, char>)">;
@@ -608,10 +608,9 @@ let Features = "avx2", Attributes = [NoThrow, Const, RequiredVectorWidth<256>] i
   def palignr256 : X86Builtin<"_Vector<32, char>(_Vector<32, char>, _Vector<32, char>, _Constant int)">;
 
   def pmovmskb256 : X86Builtin<"int(_Vector<32, char>)">;
-  def psadbw256 : X86Builtin<"_Vector<4, long long int>(_Vector<32, char>, _Vector<32, char>)">;
-  def psignb256 : X86Builtin<"_Vector<32, char>(_Vector<32, char>, _Vector<32, char>)">;
-  def psignw256 : X86Builtin<"_Vector<16, short>(_Vector<16, short>, _Vector<16, short>)">;
-  def psignd256 : X86Builtin<"_Vector<8, int>(_Vector<8, int>, _Vector<8, int>)">;
+  def psadbw256
+      : X86Builtin<
+            "_Vector<4, long long int>(_Vector<32, char>, _Vector<32, char>)">;
   def psllw256 : X86Builtin<"_Vector<16, short>(_Vector<16, short>, _Vector<8, short>)">;
   def pslldqi256_byteshift : X86Builtin<"_Vector<32, char>(_Vector<32, char>, _Constant int)">;
   def pslld256 : X86Builtin<"_Vector<8, int>(_Vector<8, int>, _Vector<4, int>)">;
@@ -682,7 +681,15 @@ let Features = "avx2", Attributes = [NoThrow, Const, Constexpr, RequiredVectorWi
   def phsubw256 : X86Builtin<"_Vector<16, short>(_Vector<16, short>, _Vector<16, short>)">;
   def phsubd256 : X86Builtin<"_Vector<8, int>(_Vector<8, int>, _Vector<8, int>)">;
   def phsubsw256 : X86Builtin<"_Vector<16, short>(_Vector<16, short>, _Vector<16, short>)">;
-  
+
+  def psignb256
+      : X86Builtin<"_Vector<32, char>(_Vector<32, char>, _Vector<32, char>)">;
+  def psignw256
+      : X86Builtin<
+            "_Vector<16, short>(_Vector<16, short>, _Vector<16, short>)">;
+  def psignd256
+      : X86Builtin<"_Vector<8, int>(_Vector<8, int>, _Vector<8, int>)">;
+
   def pshuflw256 : X86Builtin<"_Vector<16, short>(_Vector<16, short>, _Constant int)">;
   def pshufhw256 : X86Builtin<"_Vector<16, short>(_Vector<16, short>, _Constant int)">;
   def pshufd256  : X86Builtin<"_Vector<8, int>(_Vector<8, int>, _Constant int)">;
diff --git a/clang/lib/AST/ByteCode/InterpBuiltin.cpp b/clang/lib/AST/ByteCode/InterpBuiltin.cpp
index 0cb491063057c..cbbc17cd7c3a5 100644
--- a/clang/lib/AST/ByteCode/InterpBuiltin.cpp
+++ b/clang/lib/AST/ByteCode/InterpBuiltin.cpp
@@ -3003,6 +3003,35 @@ static bool interp__builtin_x86_insert_subvector(InterpState &S, CodePtr OpPC,
   return true;
 }
 
+static bool interp__builtin_ia32_psign_op(InterpState &S, CodePtr OpPC,
+                                          const CallExpr *Call) {
+  assert(Call->getNumArgs() == 2);
+
+  const Pointer &B = S.Stk.pop<Pointer>();
+  const Pointer &A = S.Stk.pop<Pointer>();
+  const Pointer &Result = S.Stk.peek<Pointer>();
+
+  unsigned ResultLen = A.getNumElems();
+  QualType ElemQT = getElemType(A);
+  OptPrimType ElemT = S.getContext().classify(ElemQT);
+  unsigned ElemBitWidth = S.getASTContext().getTypeSize(ElemQT);
+  bool ResultElemUnsigned = ElemQT->isUnsignedIntegerOrEnumerationType();
+
+  INT_TYPE_SWITCH_NO_BOOL(*ElemT, {
+    for (unsigned I = 0; I != ResultLen; ++I) {
+      APSInt AElem = A.elem<T>(I).toAPSInt();
+      APSInt BElem = B.elem<T>(I).toAPSInt();
+      APSInt ResultElem =
+          (BElem.isNegative() ? -AElem
+           : BElem.isZero()   ? APSInt(ElemBitWidth, ResultElemUnsigned)
+                              : AElem);
+      Result.elem<T>(I) = static_cast<T>(ResultElem);
+    }
+  });
+  Result.initializeAllElements();
+  return true;
+}
+
 static bool interp__builtin_ia32_pternlog(InterpState &S, CodePtr OpPC,
                                           const CallExpr *Call, bool MaskZ) {
   assert(Call->getNumArgs() == 5);
@@ -3630,6 +3659,14 @@ bool InterpretBuiltin(InterpState &S, CodePtr OpPC, const CallExpr *Call,
               .extractBits(16, 1);
         });
 
+  case X86::BI__builtin_ia32_psignb128:
+  case X86::BI__builtin_ia32_psignb256:
+  case X86::BI__builtin_ia32_psignw128:
+  case X86::BI__builtin_ia32_psignw256:
+  case X86::BI__builtin_ia32_psignd128:
+  case X86::BI__builtin_ia32_psignd256:
+    return interp__builtin_ia32_psign_op(S, OpPC, Call);
+
   case clang::X86::BI__builtin_ia32_pavgb128:
   case clang::X86::BI__builtin_ia32_pavgw128:
   case clang::X86::BI__builtin_ia32_pavgb256:
diff --git a/clang/lib/AST/ExprConstant.cpp b/clang/lib/AST/ExprConstant.cpp
index e308c171ed551..b9216cd89d7b7 100644
--- a/clang/lib/AST/ExprConstant.cpp
+++ b/clang/lib/AST/ExprConstant.cpp
@@ -12245,6 +12245,36 @@ bool VectorExprEvaluator::VisitCallExpr(const CallExpr *E) {
     return Success(APValue(ResultElements.data(), ResultElements.size()), E);
   }
 
+  case X86::BI__builtin_ia32_psignb128:
+  case X86::BI__builtin_ia32_psignb256:
+  case X86::BI__builtin_ia32_psignw128:
+  case X86::BI__builtin_ia32_psignw256:
+  case X86::BI__builtin_ia32_psignd128:
+  case X86::BI__builtin_ia32_psignd256: {
+    APValue ASource, BSource;
+    if (!EvaluateAsRValue(Info, E->getArg(0), ASource) ||
+        !EvaluateAsRValue(Info, E->getArg(1), BSource))
+      return false;
+    unsigned SourceLen = ASource.getVectorLength();
+    const VectorType *VT = E->getArg(0)->getType()->castAs<VectorType>();
+    QualType ElemQT = VT->getElementType();
+    unsigned ElemBitWidth = Info.Ctx.getTypeSize(ElemQT);
+    bool ResultElemUnsigned = ElemQT->isUnsignedIntegerOrEnumerationType();
+
+    SmallVector<APValue, 16> Result;
+    Result.reserve(SourceLen);
+    for (unsigned I = 0; I != SourceLen; ++I) {
+      APSInt &AElem = ASource.getVectorElt(I).getInt();
+      APSInt &BElem = BSource.getVectorElt(I).getInt();
+      APSInt ResultElem =
+          (BElem.isNegative() ? -AElem
+           : BElem.isZero()   ? APSInt(ElemBitWidth, ResultElemUnsigned)
+                              : AElem);
+      Result.emplace_back(ResultElem);
+    }
+    return Success(APValue(Result.data(), Result.size()), E);
+  }
+
   case X86::BI__builtin_ia32_blendvpd:
   case X86::BI__builtin_ia32_blendvpd256:
   case X86::BI__builtin_ia32_blendvps:
diff --git a/clang/lib/Headers/avx2intrin.h b/clang/lib/Headers/avx2intrin.h
index d35bc0e84a7a1..757085a930122 100644
--- a/clang/lib/Headers/avx2intrin.h
+++ b/clang/lib/Headers/avx2intrin.h
@@ -1976,10 +1976,9 @@ _mm256_shuffle_epi8(__m256i __a, __m256i __b) {
 /// \param __b
 ///    A 256-bit integer vector].
 /// \returns A 256-bit integer vector containing the result.
-static __inline__ __m256i __DEFAULT_FN_ATTRS256
-_mm256_sign_epi8(__m256i __a, __m256i __b)
-{
-    return (__m256i)__builtin_ia32_psignb256((__v32qi)__a, (__v32qi)__b);
+static __inline__ __m256i __DEFAULT_FN_ATTRS256_CONSTEXPR
+_mm256_sign_epi8(__m256i __a, __m256i __b) {
+  return (__m256i)__builtin_ia32_psignb256((__v32qi)__a, (__v32qi)__b);
 }
 
 /// Sets each element of the result to the corresponding element of the
@@ -1997,10 +1996,9 @@ _mm256_sign_epi8(__m256i __a, __m256i __b)
 /// \param __b
 ///    A 256-bit vector of [16 x i16].
 /// \returns A 256-bit vector of [16 x i16] containing the result.
-static __inline__ __m256i __DEFAULT_FN_ATTRS256
-_mm256_sign_epi16(__m256i __a, __m256i __b)
-{
-    return (__m256i)__builtin_ia32_psignw256((__v16hi)__a, (__v16hi)__b);
+static __inline__ __m256i __DEFAULT_FN_ATTRS256_CONSTEXPR
+_mm256_sign_epi16(__m256i __a, __m256i __b) {
+  return (__m256i)__builtin_ia32_psignw256((__v16hi)__a, (__v16hi)__b);
 }
 
 /// Sets each element of the result to the corresponding element of the
@@ -2018,10 +2016,9 @@ _mm256_sign_epi16(__m256i __a, __m256i __b)
 /// \param __b
 ///    A 256-bit vector of [8 x i32].
 /// \returns A 256-bit vector of [8 x i32] containing the result.
-static __inline__ __m256i __DEFAULT_FN_ATTRS256
-_mm256_sign_epi32(__m256i __a, __m256i __b)
-{
-    return (__m256i)__builtin_ia32_psignd256((__v8si)__a, (__v8si)__b);
+static __inline__ __m256i __DEFAULT_FN_ATTRS256_CONSTEXPR
+_mm256_sign_epi32(__m256i __a, __m256i __b) {
+  return (__m256i)__builtin_ia32_psignd256((__v8si)__a, (__v8si)__b);
 }
 
 /// Shifts each 128-bit half of the 256-bit integer vector \a a left by
diff --git a/clang/lib/Headers/tmmintrin.h b/clang/lib/Headers/tmmintrin.h
index 5d0f20f4d527d..95b32c0087ecb 100644
--- a/clang/lib/Headers/tmmintrin.h
+++ b/clang/lib/Headers/tmmintrin.h
@@ -641,10 +641,9 @@ _mm_shuffle_pi8(__m64 __a, __m64 __b) {
 ///    A 128-bit integer vector containing control bytes corresponding to
 ///    positions in the destination.
 /// \returns A 128-bit integer vector containing the resultant values.
-static __inline__ __m128i __DEFAULT_FN_ATTRS
-_mm_sign_epi8(__m128i __a, __m128i __b)
-{
-    return (__m128i)__builtin_ia32_psignb128((__v16qi)__a, (__v16qi)__b);
+static __inline__ __m128i __DEFAULT_FN_ATTRS_CONSTEXPR
+_mm_sign_epi8(__m128i __a, __m128i __b) {
+  return (__m128i)__builtin_ia32_psignb128((__v16qi)__a, (__v16qi)__b);
 }
 
 /// For each 16-bit integer in the first source operand, perform one of
@@ -667,10 +666,9 @@ _mm_sign_epi8(__m128i __a, __m128i __b)
 ///    A 128-bit integer vector containing control words corresponding to
 ///    positions in the destination.
 /// \returns A 128-bit integer vector containing the resultant values.
-static __inline__ __m128i __DEFAULT_FN_ATTRS
-_mm_sign_epi16(__m128i __a, __m128i __b)
-{
-    return (__m128i)__builtin_ia32_psignw128((__v8hi)__a, (__v8hi)__b);
+static __inline__ __m128i __DEFAULT_FN_ATTRS_CONSTEXPR
+_mm_sign_epi16(__m128i __a, __m128i __b) {
+  return (__m128i)__builtin_ia32_psignw128((__v8hi)__a, (__v8hi)__b);
 }
 
 /// For each 32-bit integer in the first source operand, perform one of
@@ -693,10 +691,9 @@ _mm_sign_epi16(__m128i __a, __m128i __b)
 ///    A 128-bit integer vector containing control doublewords corresponding to
 ///    positions in the destination.
 /// \returns A 128-bit integer vector containing the resultant values.
-static __inline__ __m128i __DEFAULT_FN_ATTRS
-_mm_sign_epi32(__m128i __a, __m128i __b)
-{
-    return (__m128i)__builtin_ia32_psignd128((__v4si)__a, (__v4si)__b);
+static __inline__ __m128i __DEFAULT_FN_ATTRS_CONSTEXPR
+_mm_sign_epi32(__m128i __a, __m128i __b) {
+  return (__m128i)__builtin_ia32_psignd128((__v4si)__a, (__v4si)__b);
 }
 
 /// For each 8-bit integer in the first source operand, perform one of
@@ -719,11 +716,10 @@ _mm_sign_epi32(__m128i __a, __m128i __b)
 ///    A 64-bit integer vector containing control bytes corresponding to
 ///    positions in the destination.
 /// \returns A 64-bit integer vector containing the resultant values.
-static __inline__ __m64 __DEFAULT_FN_ATTRS
-_mm_sign_pi8(__m64 __a, __m64 __b)
-{
-    return __trunc64(__builtin_ia32_psignb128((__v16qi)__anyext128(__a),
-                                              (__v16qi)__anyext128(__b)));
+static __inline__ __m64 __DEFAULT_FN_ATTRS_CONSTEXPR _mm_sign_pi8(__m64 __a,
+                                                                  __m64 __b) {
+  return __trunc64(__builtin_ia32_psignb128((__v16qi)__zext128(__a),
+                                            (__v16qi)__zext128(__b)));
 }
 
 /// For each 16-bit integer in the first source operand, perform one of
@@ -746,11 +742,10 @@ _mm_sign_pi8(__m64 __a, __m64 __b)
 ///    A 64-bit integer vector containing control words corresponding to
 ///    positions in the destination.
 /// \returns A 64-bit integer vector containing the resultant values.
-static __inline__ __m64 __DEFAULT_FN_ATTRS
-_mm_sign_pi16(__m64 __a, __m64 __b)
-{
-    return __trunc64(__builtin_ia32_psignw128((__v8hi)__anyext128(__a),
-                                              (__v8hi)__anyext128(__b)));
+static __inline__ __m64 __DEFAULT_FN_ATTRS_CONSTEXPR _mm_sign_pi16(__m64 __a,
+                                                                   __m64 __b) {
+  return __trunc64(
+      __builtin_ia32_psignw128((__v8hi)__zext128(__a), (__v8hi)__zext128(__b)));
 }
 
 /// For each 32-bit integer in the first source operand, perform one of
@@ -773,11 +768,10 @@ _mm_sign_pi16(__m64 __a, __m64 __b)
 ///    A 64-bit integer vector containing two control doublewords corresponding
 ///    to positions in the destination.
 /// \returns A 64-bit integer vector containing the resultant values.
-static __inline__ __m64 __DEFAULT_FN_ATTRS
-_mm_sign_pi32(__m64 __a, __m64 __b)
-{
-    return __trunc64(__builtin_ia32_psignd128((__v4si)__anyext128(__a),
-                                              (__v4si)__anyext128(__b)));
+static __inline__ __m64 __DEFAULT_FN_ATTRS_CONSTEXPR _mm_sign_pi32(__m64 __a,
+                                                                   __m64 __b) {
+  return __trunc64(
+      __builtin_ia32_psignd128((__v4si)__zext128(__a), (__v4si)__zext128(__b)));
 }
 
 #undef __anyext128
diff --git a/clang/test/CodeGen/X86/avx2-builtins.c b/clang/test/CodeGen/X86/avx2-builtins.c
index a505d70a98203..c785363e07f53 100644
--- a/clang/test/CodeGen/X86/avx2-builtins.c
+++ b/clang/test/CodeGen/X86/avx2-builtins.c
@@ -1151,23 +1151,30 @@ __m256i test_mm256_shufflelo_epi16(__m256i a) {
   return _mm256_shufflelo_epi16(a, 83);
 }
 TEST_CONSTEXPR(match_v16hi(_mm256_shufflelo_epi16(((__m256i)(__v16hi){ 0,1,2,3, 4,5,6,7, 8,9,10,11, 12,13,14,15}), 83), 3,0,1,1, 4,5,6,7, 11,8,9,9, 12,13,14,15) );
+
 __m256i test_mm256_sign_epi8(__m256i a, __m256i b) {
   // CHECK-LABEL: test_mm256_sign_epi8
   // CHECK: call <32 x i8> @llvm.x86.avx2.psign.b(<32 x i8> %{{.*}}, <32 x i8> %{{.*}})
   return _mm256_sign_epi8(a, b);
 }
+TEST_CONSTEXPR(match_v32qi(_mm256_sign_epi8(
+    (__m256i)(__v32qi){'B','r','i','g','h','t','n','e','o','n','f','o','x','j','u','m','p','s','o','v','e','r','p','r','o','g','r','a','m','m','e','r'},
+    (__m256i)(__v32qi){0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,'t','h','i','s'}),
+    0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,'m','m','e','r'));
 
 __m256i test_mm256_sign_epi16(__m256i a, __m256i b) {
   // CHECK-LABEL: test_mm256_sign_epi16
   // CHECK: call <16 x i16> @llvm.x86.avx2.psign.w(<16 x i16> %{{.*}}, <16 x i16> %{{.*}})
   return _mm256_sign_epi16(a, b);
 }
+TEST_CONSTEXPR(match_v16hi(_mm256_sign_epi16((__m256i)(__v16hi){0x77,0x77,0xbe,0xbe, -0x9,-0x9,-0x8,-0x8, 0,0,0,0, 0,0,0,0}, (__m256i)(__v16hi){-1,-256,1,256, -512,-1028,512,1028, -2048,-4096,'h','i', 'b','y','e','!'}), -0x77,-0x77,0xbe,0xbe, 0x9,0x9,-0x8,-0x8, 0,0,0,0, 0,0,0,0));
 
 __m256i test_mm256_sign_epi32(__m256i a, __m256i b) {
   // CHECK-LABEL: test_mm256_sign_epi32
   // CHECK: call <8 x i32> @llvm.x86.avx2.psign.d(<8 x i32> %{{.*}}, <8 x i32> %{{.*}})
   return _mm256_sign_epi32(a, b);
 }
+TEST_CONSTEXPR(match_v8si(_mm256_sign_epi32((__m256i)(__v8si){0xbeef,0xfeed,0xbead,0xdeed,'o','o','p','s'}, (__m256i)(__v8si){0,0,0,0,-1,-1,-1,-1}), 0,0,0,0, -'o',-'o',-'p',-'s'));
 
 __m256i test_mm256_slli_epi16(__m256i a) {
   // CHECK-LABEL: test_mm256_slli_epi16
diff --git a/clang/test/CodeGen/X86/mmx-builtins.c b/clang/test/CodeGen/X86/mmx-builtins.c
index c1ac57b44e58d..0065b87108914 100644
--- a/clang/test/CodeGen/X86/mmx-builtins.c
+++ b/clang/test/CodeGen/X86/mmx-builtins.c
@@ -598,23 +598,28 @@ __m64 test_mm_shuffle_pi16(__m64 a) {
   return _mm_shuffle_pi16(a, 3);
 }
 TEST_CONSTEXPR(match_v4hi(_mm_shuffle_pi16(((__m64)(__v4hi){0,1,2,3}), 3), 3,0,0,0));
+
 __m64 test_mm_sign_pi8(__m64 a, __m64 b) {
   // CHECK-LABEL: test_mm_sign_pi8
   // CHECK: call <16 x i8> @llvm.x86.ssse3.psign.b.128(
   return _mm_sign_pi8(a, b);
 }
+TEST_CONSTEXPR(match_v8qi(_mm_sign_pi8((__m64)(__v8qi){0,0,0,0, 0,0,0,0}, (__m64)(__v8qi){0,0,0,0, 0,0,0,0}), 0,0,0,0, 0,0,0,0));
+TEST_CONSTEXPR(match_v8qi(_mm_sign_pi8((__m64)(__v8qi){6,7,6,7, 6,7,6,7}, (__m64)(__v8qi){1,1,1,1, 0,0,0,0}), 6,7,6,7, 0,0,0,0));
 
 __m64 test_mm_sign_pi16(__m64 a, __m64 b) {
   // CHECK-LABEL: test_mm_sign_pi16
   // CHECK: call <8 x i16> @llvm.x86.ssse3.psign.w.128(
   return _mm_sign_pi16(a, b);
 }
+TEST_CONSTEXPR(match_v4hi(_mm_sign_pi16((__m64)(__v4hi){-1,0,1,0}, (__m64)(__v4hi){1,0,-1,0}), -1,0,-1,0));
 
 __m64 test_mm_sign_pi32(__m64 a, __m64 b) {
   // CHECK-LABEL: test_mm_sign_pi32
   // CHECK: call <4 x i32> @llvm.x86.ssse3.psign.d.128(
   return _mm_sign_pi32(a, b);
 }
+TEST_CONSTEXPR(match_v2si(_mm_sign_pi32((__m64)(__v2si){0x7FFF, -1}, (__m64)(__v2si){-1, 0x7FFF}), -0x7FFF, -1));
 
 __m64 test_mm_sll_pi16(__m64 a, __m64 b) {
   // CHECK-LABEL: test_mm_sll_pi16
diff --git a/clang/test/CodeGen/X86/ssse3-builtins.c b/clang/test/CodeGen/X86/ssse3-builtins.c
index f70afc01a1963..d3fde1e2de653 100644
--- a/clang/test/CodeGen/X86/ssse3-builtins.c
+++ b/clang/test/CodeGen/X86/ssse3-builtins.c
@@ -125,15 +125,18 @@ __m128i test_mm_sign_epi8(__m128i a, __m128i b) {
   // CHECK: call <16 x i8> @llvm.x86.ssse3.psign.b.128(<16 x i8> %{{.*}}, <16 x i8> %{{.*}})
   return _mm_sign_epi8(a, b);
 }
+TEST_CONSTEXPR(match_v16qi(_mm_sign_epi8((__m128i)(__v16qi){'g','r','i','n','d','i','n','g', 'l','e','e','t','c','o','d','e'}, (__m128i)(__v16qi){0,1,0,1, 1,1,0,0, 0,0,1,1, 1,0,1,0}), 0,'r',0,'n', 'd','i',0,0, 0,0,'e','t', 'c',0,'d',0));
 
 __m128i test_mm_sign_epi16(__m128i a, __m128i b) {
   // CHECK-LABEL: test_mm_sign_epi16
   // CHECK: call <8 x i16> @llvm.x86.ssse3.psign.w.128(<8 x i16> %{{.*}}, <8 x i16> %{{.*}})
   return _mm_sign_epi16(a, b);
 }
+TEST_CONSTEXPR(match_v8hi(_mm_sign_epi16((__m128i)(__v8hi){0,-2,0,-4,0,-6,0,-8}, (__m128i)(__v8hi){-1,-2,-3,-4,-5,-6,7,-8}), 0,2,0,4,0,6,0,8));
 
 __m128i test_mm_sign_epi32(__m128i a, __m128i b) {
   // CHECK-LABEL: test_mm_sign_epi32
   // CHECK: call <4 x i32> @llvm.x86.ssse3.psign.d.128(<4 x i32> %{{.*}}, <4 x i32> %{{.*}})
   return _mm_sign_epi32(a, b);
 }
+TEST_CONSTEXPR(match_v4si(_mm_sign_epi32((__m128i)(__v4si){-1,-2,-3,-4}, (__m128i)(__v4si){-4,-3,-2,-1}), 1,2,3,4));

clang/lib/AST/ByteCode/InterpBuiltin.cpp

clang/lib/AST/ExprConstant.cpp

clang/test/CodeGen/X86/avx2-builtins.c

clang/lib/AST/ExprConstant.cpp

clang/lib/AST/ByteCode/InterpBuiltin.cpp

kimsh02 · 2025-10-22T04:03:41Z

This works

    return interp__builtin_elementwise_int_binop(
        S, OpPC, Call, [](const APInt &AElem, const APInt &BElem) {
          if (BElem.isZero())
            return APInt::getZero(AElem.getBitWidth());
          if (BElem.isNegative())
            return -AElem;
          return AElem;
        });

but not

    return interp__builtin_elementwise_int_binop(
        S, OpPC, Call, [](const APSInt &AElem, const APSInt &BElem) {
          if (BElem.isZero())
            return APInt::getZero(AElem.getBitWidth());
          if (BElem.isNegative())
            return static_cast<APInt>(-AElem);
          return static_cast<APInt>(AElem);
        })

for negative char element test cases. Any idea why?

RKSimon · 2025-10-22T08:13:46Z

We have char signedness test coverage (as some people have to build with -fno-signed-char) - so APSInt will treat some cases as uchar and its isNegative() override won't return true then. APInt methods leaves you to handle signedness manually so its method will always work.

I recommend you take a look at the APSInt.h and APInt.h files to get a better understanding of whats going on as APSInt/APInt interaction can cause surprises!

RKSimon · 2025-10-22T08:14:36Z

clang/lib/AST/ExprConstant.cpp

+  case X86::BI__builtin_ia32_psignd128:
+  case X86::BI__builtin_ia32_psignd256:
+    return EvaluateBinOpExpr(
+        [](const APInt &AElem, const APInt &BElem) -> APInt {


Suggested change

[](const APInt &AElem, const APInt &BElem) -> APInt {

[](const APInt &AElem, const APInt &BElem) {

RKSimon · 2025-10-22T08:15:52Z

clang/lib/Headers/tmmintrin.h

+static __inline__ __m64 __DEFAULT_FN_ATTRS_CONSTEXPR _mm_sign_pi8(__m64 __a,
+                                                                  __m64 __b) {
+  return __trunc64(__builtin_ia32_psignb128((__v16qi)__zext128(__a),
+                                            (__v16qi)__zext128(__b)));


If these were the last uses of __anyext128 we should remove the define/undef from tmmintrin.h

RKSimon self-requested a review October 18, 2025 10:49

RKSimon changed the title ~~Draft~~ [Clang] VectorExprEvaluator::VisitCallExpr / InterpretBuiltin - allow MMX/SSE/AVX2 PSIGN intrinsics to be used in constexpr Oct 18, 2025

RKSimon requested changes Oct 18, 2025

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kimsh02 force-pushed the x86-psign branch from 5c58df9 to b1b4415 Compare October 20, 2025 16:53

kimsh02 marked this pull request as ready for review October 20, 2025 16:53

llvmbot added clang Clang issues not falling into any other category backend:X86 clang:frontend Language frontend issues, e.g. anything involving "Sema" clang:headers Headers provided by Clang, e.g. for intrinsics clang:bytecode Issues for the clang bytecode constexpr interpreter labels Oct 20, 2025

kimsh02 requested a review from RKSimon October 20, 2025 16:55

RKSimon requested changes Oct 20, 2025

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kimsh02 requested a review from RKSimon October 20, 2025 18:30

Squash

f236b64

kimsh02 force-pushed the x86-psign branch from 7f68ad8 to f236b64 Compare October 20, 2025 18:34

Fix rebase

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kimsh02 added 2 commits October 21, 2025 02:29

Fix testcases

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Merge branch 'main' into x86-psign

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[Clang] VectorExprEvaluator::VisitCallExpr / InterpretBuiltin - allow MMX/SSE/AVX2 PSIGN intrinsics to be used in constexpr #163685

[Clang] VectorExprEvaluator::VisitCallExpr / InterpretBuiltin - allow MMX/SSE/AVX2 PSIGN intrinsics to be used in constexpr #163685

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	[](const APInt &AElem, const APInt &BElem) -> APInt {
	[](const APInt &AElem, const APInt &BElem) {

[Clang] VectorExprEvaluator::VisitCallExpr / InterpretBuiltin - allow MMX/SSE/AVX2 PSIGN intrinsics to be used in constexpr #163685

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[Clang] VectorExprEvaluator::VisitCallExpr / InterpretBuiltin - allow MMX/SSE/AVX2 PSIGN intrinsics to be used in constexpr #163685

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