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[Headers][X86] Allow vector bitcast intrinsics to be used in constexpr #167180

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@Red-RobinHood Red-RobinHood commented Nov 8, 2025 •
edited by RKSimon
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Fixes #156348

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@llvmbot llvmbot added clang Clang issues not falling into any other category backend:X86 clang:headers Headers provided by Clang, e.g. for intrinsics labels Nov 8, 2025
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llvmbot commented Nov 8, 2025 •
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@llvm/pr-subscribers-backend-x86

Author: None (Red-RobinHood)

Changes

Full diff: https://github.com/llvm/llvm-project/pull/167180.diff

2 Files Affected:

  • (modified) clang/lib/Headers/avx512fintrin.h (+10-10)
  • (modified) clang/lib/Headers/avx512fp16intrin.h (+18-18)
diff --git a/clang/lib/Headers/avx512fintrin.h b/clang/lib/Headers/avx512fintrin.h
index 997e9608e112f..d3048f9825e4d 100644
--- a/clang/lib/Headers/avx512fintrin.h
+++ b/clang/lib/Headers/avx512fintrin.h
@@ -409,19 +409,19 @@ _mm512_castps256_ps512(__m256 __a)
                                  1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15);
 }
 
-static __inline __m128d __DEFAULT_FN_ATTRS512
+static __inline __m128d __DEFAULT_FN_ATTRS512_CONSTEXPR
 _mm512_castpd512_pd128(__m512d __a)
 {
   return __builtin_shufflevector(__a, __a, 0, 1);
 }
 
-static __inline __m256d __DEFAULT_FN_ATTRS512
+static __inline __m256d __DEFAULT_FN_ATTRS512_CONSTEXPR
 _mm512_castpd512_pd256 (__m512d __A)
 {
   return __builtin_shufflevector(__A, __A, 0, 1, 2, 3);
 }
 
-static __inline __m128 __DEFAULT_FN_ATTRS512
+static __inline __m128 __DEFAULT_FN_ATTRS512_CONSTEXPR
 _mm512_castps512_ps128(__m512 __a)
 {
   return __builtin_shufflevector(__a, __a, 0, 1, 2, 3);
@@ -432,13 +432,13 @@ _mm512_castps512_ps256(__m512 __A) {
   return __builtin_shufflevector(__A, __A, 0, 1, 2, 3, 4, 5, 6, 7);
 }
 
-static __inline __m512 __DEFAULT_FN_ATTRS512
+static __inline __m512 __DEFAULT_FN_ATTRS512_CONSTEXPR
 _mm512_castpd_ps (__m512d __A)
 {
   return (__m512) (__A);
 }
 
-static __inline __m512i __DEFAULT_FN_ATTRS512
+static __inline __m512i __DEFAULT_FN_ATTRS512_CONSTEXPR
 _mm512_castpd_si512 (__m512d __A)
 {
   return (__m512i) (__A);
@@ -453,13 +453,13 @@ _mm512_castpd128_pd512 (__m128d __A)
       __B, 0, 1, 2, 3, 4, 5, 6, 7);
 }
 
-static __inline __m512d __DEFAULT_FN_ATTRS512
+static __inline __m512d __DEFAULT_FN_ATTRS512_CONSTEXPR
 _mm512_castps_pd (__m512 __A)
 {
   return (__m512d) (__A);
 }
 
-static __inline __m512i __DEFAULT_FN_ATTRS512
+static __inline __m512i __DEFAULT_FN_ATTRS512_CONSTEXPR
 _mm512_castps_si512 (__m512 __A)
 {
   return (__m512i) (__A);
@@ -489,19 +489,19 @@ _mm512_castsi256_si512 (__m256i __A)
    return  __builtin_shufflevector( __A, __builtin_nondeterministic_value(__A), 0, 1, 2, 3, 4, 5, 6, 7);
 }
 
-static __inline __m512 __DEFAULT_FN_ATTRS512
+static __inline __m512 __DEFAULT_FN_ATTRS512_CONSTEXPR
 _mm512_castsi512_ps (__m512i __A)
 {
   return (__m512) (__A);
 }
 
-static __inline __m512d __DEFAULT_FN_ATTRS512
+static __inline __m512d __DEFAULT_FN_ATTRS512_CONSTEXPR
 _mm512_castsi512_pd (__m512i __A)
 {
   return (__m512d) (__A);
 }
 
-static __inline __m128i __DEFAULT_FN_ATTRS512
+static __inline __m128i __DEFAULT_FN_ATTRS512_CONSTEXPR
 _mm512_castsi512_si128 (__m512i __A)
 {
   return (__m128i)__builtin_shufflevector(__A, __A , 0, 1);
diff --git a/clang/lib/Headers/avx512fp16intrin.h b/clang/lib/Headers/avx512fp16intrin.h
index 25051228f3e0a..f246fe0273c9a 100644
--- a/clang/lib/Headers/avx512fp16intrin.h
+++ b/clang/lib/Headers/avx512fp16intrin.h
@@ -117,78 +117,78 @@ _mm512_set1_pch(_Float16 _Complex __h) {
   return (__m512h)_mm512_set1_ps(__builtin_bit_cast(float, __h));
 }
 
-static __inline__ __m128 __DEFAULT_FN_ATTRS128 _mm_castph_ps(__m128h __a) {
+static __inline__ __m128 __DEFAULT_FN_ATTRS128_CONSTEXPR _mm_castph_ps(__m128h __a) {
   return (__m128)__a;
 }
 
-static __inline__ __m256 __DEFAULT_FN_ATTRS256 _mm256_castph_ps(__m256h __a) {
+static __inline__ __m256 __DEFAULT_FN_ATTRS256_CONSTEXPR _mm256_castph_ps(__m256h __a) {
   return (__m256)__a;
 }
 
-static __inline__ __m512 __DEFAULT_FN_ATTRS512 _mm512_castph_ps(__m512h __a) {
+static __inline__ __m512 __DEFAULT_FN_ATTRS512_CONSTEXPR _mm512_castph_ps(__m512h __a) {
   return (__m512)__a;
 }
 
-static __inline__ __m128d __DEFAULT_FN_ATTRS128 _mm_castph_pd(__m128h __a) {
+static __inline__ __m128d __DEFAULT_FN_ATTRS128_CONSTEXPR _mm_castph_pd(__m128h __a) {
   return (__m128d)__a;
 }
 
-static __inline__ __m256d __DEFAULT_FN_ATTRS256 _mm256_castph_pd(__m256h __a) {
+static __inline__ __m256d __DEFAULT_FN_ATTRS256_CONSTEXPR _mm256_castph_pd(__m256h __a) {
   return (__m256d)__a;
 }
 
-static __inline__ __m512d __DEFAULT_FN_ATTRS512 _mm512_castph_pd(__m512h __a) {
+static __inline__ __m512d __DEFAULT_FN_ATTRS512_CONSTEXPR _mm512_castph_pd(__m512h __a) {
   return (__m512d)__a;
 }
 
-static __inline__ __m128i __DEFAULT_FN_ATTRS128 _mm_castph_si128(__m128h __a) {
+static __inline__ __m128i __DEFAULT_FN_ATTRS128_CONSTEXPR _mm_castph_si128(__m128h __a) {
   return (__m128i)__a;
 }
 
-static __inline__ __m256i __DEFAULT_FN_ATTRS256
+static __inline__ __m256i __DEFAULT_FN_ATTRS256_CONSTEXPR
 _mm256_castph_si256(__m256h __a) {
   return (__m256i)__a;
 }
 
-static __inline__ __m512i __DEFAULT_FN_ATTRS512
+static __inline__ __m512i __DEFAULT_FN_ATTRS512_CONSTEXPR
 _mm512_castph_si512(__m512h __a) {
   return (__m512i)__a;
 }
 
-static __inline__ __m128h __DEFAULT_FN_ATTRS128 _mm_castps_ph(__m128 __a) {
+static __inline__ __m128h __DEFAULT_FN_ATTRS128_CONSTEXPR _mm_castps_ph(__m128 __a) {
   return (__m128h)__a;
 }
 
-static __inline__ __m256h __DEFAULT_FN_ATTRS256 _mm256_castps_ph(__m256 __a) {
+static __inline__ __m256h __DEFAULT_FN_ATTRS256_CONSTEXPR _mm256_castps_ph(__m256 __a) {
   return (__m256h)__a;
 }
 
-static __inline__ __m512h __DEFAULT_FN_ATTRS512 _mm512_castps_ph(__m512 __a) {
+static __inline__ __m512h __DEFAULT_FN_ATTRS512_CONSTEXPR _mm512_castps_ph(__m512 __a) {
   return (__m512h)__a;
 }
 
-static __inline__ __m128h __DEFAULT_FN_ATTRS128 _mm_castpd_ph(__m128d __a) {
+static __inline__ __m128h __DEFAULT_FN_ATTRS128_CONSTEXPR _mm_castpd_ph(__m128d __a) {
   return (__m128h)__a;
 }
 
-static __inline__ __m256h __DEFAULT_FN_ATTRS256 _mm256_castpd_ph(__m256d __a) {
+static __inline__ __m256h __DEFAULT_FN_ATTRS256_CONSTEXPR _mm256_castpd_ph(__m256d __a) {
   return (__m256h)__a;
 }
 
-static __inline__ __m512h __DEFAULT_FN_ATTRS512 _mm512_castpd_ph(__m512d __a) {
+static __inline__ __m512h __DEFAULT_FN_ATTRS512_CONSTEXPR _mm512_castpd_ph(__m512d __a) {
   return (__m512h)__a;
 }
 
-static __inline__ __m128h __DEFAULT_FN_ATTRS128 _mm_castsi128_ph(__m128i __a) {
+static __inline__ __m128h __DEFAULT_FN_ATTRS128_CONSTEXPR _mm_castsi128_ph(__m128i __a) {
   return (__m128h)__a;
 }
 
-static __inline__ __m256h __DEFAULT_FN_ATTRS256
+static __inline__ __m256h __DEFAULT_FN_ATTRS256_CONSTEXPR
 _mm256_castsi256_ph(__m256i __a) {
   return (__m256h)__a;
 }
 
-static __inline__ __m512h __DEFAULT_FN_ATTRS512
+static __inline__ __m512h __DEFAULT_FN_ATTRS512_CONSTEXPR
 _mm512_castsi512_ph(__m512i __a) {
   return (__m512h)__a;
 }

@RKSimon RKSimon self-requested a review November 8, 2025 23:39
@Red-RobinHood
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Red-RobinHood commented Nov 9, 2025 •
edited
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I will add tests in a few days. Working on them. Should I use random values or +/-0.0 as placeholders?

@RKSimon RKSimon changed the title Attempt to fix Issue 156348 [Headers][X86] Allow vector bitcast intrinsics to be used in constexpr Nov 9, 2025
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github-actions bot commented Nov 9, 2025

⚠️ C/C++ code formatter, clang-format found issues in your code. ⚠️

You can test this locally with the following command: 
git-clang-format --diff origin/main HEAD --extensions h -- clang/lib/Headers/avx512fintrin.h clang/lib/Headers/avx512fp16intrin.h --diff_from_common_commit

⚠️
The reproduction instructions above might return results for more than one PR
in a stack if you are using a stacked PR workflow. You can limit the results by
changing origin/main to the base branch/commit you want to compare against.
⚠️

View the diff from clang-format here. 
diff --git a/clang/lib/Headers/avx512fintrin.h b/clang/lib/Headers/avx512fintrin.h
index d3048f982..6701035dc 100644
--- a/clang/lib/Headers/avx512fintrin.h
+++ b/clang/lib/Headers/avx512fintrin.h
@@ -410,20 +410,17 @@ _mm512_castps256_ps512(__m256 __a)
 }
 
 static __inline __m128d __DEFAULT_FN_ATTRS512_CONSTEXPR
-_mm512_castpd512_pd128(__m512d __a)
-{
+_mm512_castpd512_pd128(__m512d __a) {
   return __builtin_shufflevector(__a, __a, 0, 1);
 }
 
 static __inline __m256d __DEFAULT_FN_ATTRS512_CONSTEXPR
-_mm512_castpd512_pd256 (__m512d __A)
-{
+_mm512_castpd512_pd256(__m512d __A) {
   return __builtin_shufflevector(__A, __A, 0, 1, 2, 3);
 }
 
 static __inline __m128 __DEFAULT_FN_ATTRS512_CONSTEXPR
-_mm512_castps512_ps128(__m512 __a)
-{
+_mm512_castps512_ps128(__m512 __a) {
   return __builtin_shufflevector(__a, __a, 0, 1, 2, 3);
 }
 
@@ -433,14 +430,12 @@ _mm512_castps512_ps256(__m512 __A) {
 }
 
 static __inline __m512 __DEFAULT_FN_ATTRS512_CONSTEXPR
-_mm512_castpd_ps (__m512d __A)
-{
+_mm512_castpd_ps(__m512d __A) {
   return (__m512) (__A);
 }
 
 static __inline __m512i __DEFAULT_FN_ATTRS512_CONSTEXPR
-_mm512_castpd_si512 (__m512d __A)
-{
+_mm512_castpd_si512(__m512d __A) {
   return (__m512i) (__A);
 }
 
@@ -454,14 +449,12 @@ _mm512_castpd128_pd512 (__m128d __A)
 }
 
 static __inline __m512d __DEFAULT_FN_ATTRS512_CONSTEXPR
-_mm512_castps_pd (__m512 __A)
-{
+_mm512_castps_pd(__m512 __A) {
   return (__m512d) (__A);
 }
 
 static __inline __m512i __DEFAULT_FN_ATTRS512_CONSTEXPR
-_mm512_castps_si512 (__m512 __A)
-{
+_mm512_castps_si512(__m512 __A) {
   return (__m512i) (__A);
 }
 
@@ -490,20 +483,17 @@ _mm512_castsi256_si512 (__m256i __A)
 }
 
 static __inline __m512 __DEFAULT_FN_ATTRS512_CONSTEXPR
-_mm512_castsi512_ps (__m512i __A)
-{
+_mm512_castsi512_ps(__m512i __A) {
   return (__m512) (__A);
 }
 
 static __inline __m512d __DEFAULT_FN_ATTRS512_CONSTEXPR
-_mm512_castsi512_pd (__m512i __A)
-{
+_mm512_castsi512_pd(__m512i __A) {
   return (__m512d) (__A);
 }
 
 static __inline __m128i __DEFAULT_FN_ATTRS512_CONSTEXPR
-_mm512_castsi512_si128 (__m512i __A)
-{
+_mm512_castsi512_si128(__m512i __A) {
   return (__m128i)__builtin_shufflevector(__A, __A , 0, 1);
 }
 
diff --git a/clang/lib/Headers/avx512fp16intrin.h b/clang/lib/Headers/avx512fp16intrin.h
index f246fe027..2f4325f07 100644
--- a/clang/lib/Headers/avx512fp16intrin.h
+++ b/clang/lib/Headers/avx512fp16intrin.h
@@ -117,31 +117,38 @@ _mm512_set1_pch(_Float16 _Complex __h) {
   return (__m512h)_mm512_set1_ps(__builtin_bit_cast(float, __h));
 }
 
-static __inline__ __m128 __DEFAULT_FN_ATTRS128_CONSTEXPR _mm_castph_ps(__m128h __a) {
+static __inline__ __m128 __DEFAULT_FN_ATTRS128_CONSTEXPR
+_mm_castph_ps(__m128h __a) {
   return (__m128)__a;
 }
 
-static __inline__ __m256 __DEFAULT_FN_ATTRS256_CONSTEXPR _mm256_castph_ps(__m256h __a) {
+static __inline__ __m256 __DEFAULT_FN_ATTRS256_CONSTEXPR
+_mm256_castph_ps(__m256h __a) {
   return (__m256)__a;
 }
 
-static __inline__ __m512 __DEFAULT_FN_ATTRS512_CONSTEXPR _mm512_castph_ps(__m512h __a) {
+static __inline__ __m512 __DEFAULT_FN_ATTRS512_CONSTEXPR
+_mm512_castph_ps(__m512h __a) {
   return (__m512)__a;
 }
 
-static __inline__ __m128d __DEFAULT_FN_ATTRS128_CONSTEXPR _mm_castph_pd(__m128h __a) {
+static __inline__ __m128d __DEFAULT_FN_ATTRS128_CONSTEXPR
+_mm_castph_pd(__m128h __a) {
   return (__m128d)__a;
 }
 
-static __inline__ __m256d __DEFAULT_FN_ATTRS256_CONSTEXPR _mm256_castph_pd(__m256h __a) {
+static __inline__ __m256d __DEFAULT_FN_ATTRS256_CONSTEXPR
+_mm256_castph_pd(__m256h __a) {
   return (__m256d)__a;
 }
 
-static __inline__ __m512d __DEFAULT_FN_ATTRS512_CONSTEXPR _mm512_castph_pd(__m512h __a) {
+static __inline__ __m512d __DEFAULT_FN_ATTRS512_CONSTEXPR
+_mm512_castph_pd(__m512h __a) {
   return (__m512d)__a;
 }
 
-static __inline__ __m128i __DEFAULT_FN_ATTRS128_CONSTEXPR _mm_castph_si128(__m128h __a) {
+static __inline__ __m128i __DEFAULT_FN_ATTRS128_CONSTEXPR
+_mm_castph_si128(__m128h __a) {
   return (__m128i)__a;
 }
 
@@ -155,31 +162,38 @@ _mm512_castph_si512(__m512h __a) {
   return (__m512i)__a;
 }
 
-static __inline__ __m128h __DEFAULT_FN_ATTRS128_CONSTEXPR _mm_castps_ph(__m128 __a) {
+static __inline__ __m128h __DEFAULT_FN_ATTRS128_CONSTEXPR
+_mm_castps_ph(__m128 __a) {
   return (__m128h)__a;
 }
 
-static __inline__ __m256h __DEFAULT_FN_ATTRS256_CONSTEXPR _mm256_castps_ph(__m256 __a) {
+static __inline__ __m256h __DEFAULT_FN_ATTRS256_CONSTEXPR
+_mm256_castps_ph(__m256 __a) {
   return (__m256h)__a;
 }
 
-static __inline__ __m512h __DEFAULT_FN_ATTRS512_CONSTEXPR _mm512_castps_ph(__m512 __a) {
+static __inline__ __m512h __DEFAULT_FN_ATTRS512_CONSTEXPR
+_mm512_castps_ph(__m512 __a) {
   return (__m512h)__a;
 }
 
-static __inline__ __m128h __DEFAULT_FN_ATTRS128_CONSTEXPR _mm_castpd_ph(__m128d __a) {
+static __inline__ __m128h __DEFAULT_FN_ATTRS128_CONSTEXPR
+_mm_castpd_ph(__m128d __a) {
   return (__m128h)__a;
 }
 
-static __inline__ __m256h __DEFAULT_FN_ATTRS256_CONSTEXPR _mm256_castpd_ph(__m256d __a) {
+static __inline__ __m256h __DEFAULT_FN_ATTRS256_CONSTEXPR
+_mm256_castpd_ph(__m256d __a) {
   return (__m256h)__a;
 }
 
-static __inline__ __m512h __DEFAULT_FN_ATTRS512_CONSTEXPR _mm512_castpd_ph(__m512d __a) {
+static __inline__ __m512h __DEFAULT_FN_ATTRS512_CONSTEXPR
+_mm512_castpd_ph(__m512d __a) {
   return (__m512h)__a;
 }
 
-static __inline__ __m128h __DEFAULT_FN_ATTRS128_CONSTEXPR _mm_castsi128_ph(__m128i __a) {
+static __inline__ __m128h __DEFAULT_FN_ATTRS128_CONSTEXPR
+_mm_castsi128_ph(__m128i __a) {
   return (__m128h)__a;
 }

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[Headers][X86] Allow vector bitcast intrinsics to be used in constexpr

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