[clang] b178821 - [X86] avx512fp16intrin.h - allow fp16 truncation casts to be used in constexpr (#162250)

[via cfe-commits]

Author: Simon Pilgrim
Date: 2025-10-07T10:00:31Z
New Revision: b1788211d3750292fc10027fb649b359fd6cd0d7

URL: https://github.com/llvm/llvm-project/commit/b1788211d3750292fc10027fb649b359fd6cd0d7
DIFF: https://github.com/llvm/llvm-project/commit/b1788211d3750292fc10027fb649b359fd6cd0d7.diff

LOG: [X86] avx512fp16intrin.h - allow fp16 truncation casts to be used in constexpr (#162250)

_mm256_castph256_ph128
_mm512_castph512_ph128
_mm512_castph512_ph256

Part of #156348

Added: 
    

Modified: 
    clang/lib/Headers/avx512fp16intrin.h
    clang/test/CodeGen/X86/avx512fp16-builtins.c

Removed: 
    


################################################################################
diff  --git a/clang/lib/Headers/avx512fp16intrin.h b/clang/lib/Headers/avx512fp16intrin.h
index bd47ea6a783b2..142cc079c2c4b 100644
--- a/clang/lib/Headers/avx512fp16intrin.h
+++ b/clang/lib/Headers/avx512fp16intrin.h
@@ -193,17 +193,17 @@ _mm512_castsi512_ph(__m512i __a) {
   return (__m512h)__a;
 }
 
-static __inline__ __m128h __DEFAULT_FN_ATTRS256
+static __inline__ __m128h __DEFAULT_FN_ATTRS256_CONSTEXPR
 _mm256_castph256_ph128(__m256h __a) {
   return __builtin_shufflevector(__a, __a, 0, 1, 2, 3, 4, 5, 6, 7);
 }
 
-static __inline__ __m128h __DEFAULT_FN_ATTRS512
+static __inline__ __m128h __DEFAULT_FN_ATTRS512_CONSTEXPR
 _mm512_castph512_ph128(__m512h __a) {
   return __builtin_shufflevector(__a, __a, 0, 1, 2, 3, 4, 5, 6, 7);
 }
 
-static __inline__ __m256h __DEFAULT_FN_ATTRS512
+static __inline__ __m256h __DEFAULT_FN_ATTRS512_CONSTEXPR
 _mm512_castph512_ph256(__m512h __a) {
   return __builtin_shufflevector(__a, __a, 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11,
                                  12, 13, 14, 15);

diff  --git a/clang/test/CodeGen/X86/avx512fp16-builtins.c b/clang/test/CodeGen/X86/avx512fp16-builtins.c
index 820104db08e30..2befff05c7903 100644
--- a/clang/test/CodeGen/X86/avx512fp16-builtins.c
+++ b/clang/test/CodeGen/X86/avx512fp16-builtins.c
@@ -341,18 +341,21 @@ __m128h test_mm256_castph256_ph128(__m256h __a) {
   // CHECK: shufflevector <16 x half> %{{.*}}, <16 x half> %{{.*}}, <8 x i32> <i32 0, i32 1, i32 2, i32 3, i32 4, i32 5, i32 6, i32 7>
   return _mm256_castph256_ph128(__a);
 }
+TEST_CONSTEXPR(match_m128h(_mm256_castph256_ph128((__m256h){-1.0, 2.0, -3.0, 4.0, -5.0, 6.0, -7.0, 8.0, -9.0, 10.0, -11.0, 12.0, -13.0, 14.0, -15.0, -16.0}), -1.0, 2.0, -3.0, 4.0, -5.0, 6.0, -7.0, 8.0));
 
 __m128h test_mm512_castph512_ph128(__m512h __a) {
   // CHECK-LABEL: test_mm512_castph512_ph128
   // CHECK: shufflevector <32 x half> %{{.*}}, <32 x half> %{{.*}}, <8 x i32> <i32 0, i32 1, i32 2, i32 3, i32 4, i32 5, i32 6, i32 7>
   return _mm512_castph512_ph128(__a);
 }
+TEST_CONSTEXPR(match_m128h(_mm512_castph512_ph128((__m512h){0.0, -1.0, 2.0, -3.0, 4.0, -5.0, 6.0, -7.0, 8.0, -9.0, 10.0, -11.0, 12.0, -13.0, 14.0, -15.0, -16.0, -17.0, 18.0, -19.0, 20.0, -21.0, 22.0, -23.0, 24.0, -25.0, 26.0, -27.0, 28.0, -29.0, 30.0, -31.0}), 0.0, -1.0, 2.0, -3.0, 4.0, -5.0, 6.0, -7.0));
 
 __m256h test_mm512_castph512_ph256(__m512h __a) {
   // CHECK-LABEL: test_mm512_castph512_ph256
   // CHECK: shufflevector <32 x half> %{{.*}}, <32 x half> %{{.*}}, <16 x i32> <i32 0, i32 1, i32 2, i32 3, i32 4, i32 5, i32 6, i32 7, i32 8, i32 9, i32 10, i32 11, i32 12, i32 13, i32 14, i32 15>
   return _mm512_castph512_ph256(__a);
 }
+TEST_CONSTEXPR(match_m256h(_mm512_castph512_ph256((__m512h){-1.0, 2.0, -3.0, 4.0, -5.0, 6.0, -7.0, 8.0, -9.0, 10.0, -11.0, 12.0, -13.0, 14.0, -15.0, -16.0, -17.0, 18.0, -19.0, 20.0, -21.0, 22.0, -23.0, 24.0, -25.0, 26.0, -27.0, 28.0, -29.0, 30.0, -31.0, 32.0}), -1.0, 2.0, -3.0, 4.0, -5.0, 6.0, -7.0, 8.0, -9.0, 10.0, -11.0, 12.0, -13.0, 14.0, -15.0, -16.0));
 
 __m256h test_mm256_castph128_ph256(__m128h __a) {
   // CHECK-LABEL: test_mm256_castph128_ph256