Function that should have been pure, by cet. Edit contributing guidel…

…ines.

CONTRIBUTING.md

@@ -1,14 +1,25 @@
 Advice:
 
 - **GODBOLT EVERYTHING YOU COMMIT**
+  * Use `godbolt-template.d` and modify to your wished
+  * GDC (version 12 or later) with -mavx -mavx2 (the template doesn't build without -mavx)
+  * LDC (version 1.24+ or later) with -mtriple arm64, -O2, -O0, -mattr=+avx2, etc. 
 
-- Do intrinsics **one by one**, not all at once. This is very detailed work, it's not possible nor desirable to go fast while writing intrinsics. Please don't.
+
+- Do intrinsics **one by one**, not all at once. This is **very** detailed work, it's not possible nor desirable to go fast while writing intrinsics. 
+   * Please don't go fast. 
+   * Please make small PR because there is a lot of context to communicate.
+   * Get pre-approval before working on something big.
 
 - Add PERF comment anywhere you feel that something could be done faster in a supported combination: DMD D_SIMD, LDC x86_64, LDC arm64, LDC x86, GDC x86_64, with or without optimizations, with or without instruction support... 
   * If this is supposed returns a SIMD literal, does it inline?
   * Can this be faster in -O0?
   * If instruction support is not there, is the alternative path fast?
 
+- Later instruction set are allowed to use intrinsics from <= instruction sets.
+
+- Keep in mind all intrinsics should work, whatever the compiler and flags, with same semantics. This is the main appeal of the library.
+
 
 To be merged a PR:
 

source/inteli/avxintrin.d

@@ -4,6 +4,7 @@
 *
 * Copyright: Guillaume Piolat 2022.
 *            Johan Engelen 2022.
+*            cet 2024.
 * License:   $(LINK2 http://www.boost.org/LICENSE_1_0.txt, Boost License 1.0)
 */
 module inteli.avxintrin;
@@ -3300,7 +3301,7 @@ unittest
 }
 
 /// Broadcast 64-bit integer `a` to all elements of the return value.
-__m256i _mm256_set1_epi64x (long a)
+__m256i _mm256_set1_epi64x (long a) pure
 {
     return cast(__m256i)(long4(a));
 }
@@ -3459,7 +3460,7 @@ unittest
 }
 
 /// Set packed `__m256` vector with the supplied values.
-__m256 _mm256_setr_m128 (__m128 lo, __m128 hi)
+__m256 _mm256_setr_m128 (__m128 lo, __m128 hi) pure
 {
     return _mm256_set_m128(hi, lo);
 }
@@ -3473,7 +3474,7 @@ unittest
 }
 
 /// Set packed `__m256d` vector with the supplied values.
-__m256d _mm256_setr_m128d (__m128d lo, __m128d hi)
+__m256d _mm256_setr_m128d (__m128d lo, __m128d hi) pure
 {
     return _mm256_set_m128d(hi, lo);
 }
@@ -3487,7 +3488,7 @@ unittest
 }
 
 /// Set packed `__m256i` vector with the supplied values.
-__m256i _mm256_setr_m128i (__m128i lo, __m128i hi)
+__m256i _mm256_setr_m128i (__m128i lo, __m128i hi) pure
 {
     return _mm256_set_m128i(hi, lo);
 }