https://github.com/vedantjk created
https://github.com/llvm/llvm-project/pull/156381
Enable constexpr usage of vector bitcast intrinsics by changing from
`__DEFAULT_FN_ATTRS*` to
`__DEFAULT_FN_ATTRS*_CONSTEXPR` attributes.
**Updated intrinsics:**
- AVX-512 bitcast intrinsics: `_mm512_castpd_ps`, `_mm512_castps_pd`,
`_mm512_cast*_si512`,
`_mm512_castsi512_*`
- AVX-512 truncation casts: `_mm512_cast*512_*128/256`
- AVX-512 FP16 bitcast intrinsics: all `_mm*_castph_*` and `_mm*_cast*_ph`
functions
- AVX-512 FP16 truncation casts: `_mm*_castph*_ph*`
**Note:** Extension casts (e.g., `_mm512_castpd128_pd512`) remain
non-constexpr as they use
`__builtin_nondeterministic_value`, which cannot be used in constexpr
contexts.
>From 9833270e2861fe77e7e8e862d81bacbd39983895 Mon Sep 17 00:00:00 2001
From: vedantjk <vedantkodagi2...@gmail.com>
Date: Mon, 1 Sep 2025 18:02:01 -0700
Subject: [PATCH] [clang] Make vector cast intrinsics constexpr
---
clang/lib/Headers/avx512fintrin.h | 20 ++++++-------
clang/lib/Headers/avx512fp16intrin.h | 42 ++++++++++++++--------------
2 files changed, 31 insertions(+), 31 deletions(-)
diff --git a/clang/lib/Headers/avx512fintrin.h
b/clang/lib/Headers/avx512fintrin.h
index 0006e334022b6..317891dfb8c08 100644
--- a/clang/lib/Headers/avx512fintrin.h
+++ b/clang/lib/Headers/avx512fintrin.h
@@ -408,19 +408,19 @@ _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);
@@ -431,13 +431,13 @@ _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);
@@ -452,13 +452,13 @@ _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);
@@ -488,19 +488,19 @@ _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 6989b86a7b68c..b8145613d06fe 100644
--- a/clang/lib/Headers/avx512fp16intrin.h
+++ b/clang/lib/Headers/avx512fp16intrin.h
@@ -113,93 +113,93 @@ _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;
}
-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);
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