From e5987569d3dbe680f9b772d957db43e2fa18390c Mon Sep 17 00:00:00 2001
From: Aliaksei Urbanski <aliaksei.urbanski@gmail.com>
Date: Mon, 31 Mar 2025 13:23:38 +0200
Subject: [PATCH] Fix #134933: False positive SUPPORT_SSE42_BUILD

When you build Blender with optimization flags, such as `-O1` or higher, [this check](https://projects.blender.org/blender/blender/src/branch/main/build_files/cmake/macros.cmake#L572-L576) always passes, so `SUPPORT_SSE42_BUILD` is set to false positive value even when a CPU doesn't actually support `SSE4.2`.

This fix prevents a compiler from throwing away `SSE4.2` instructions.

_Best regards!_

Pull Request: https://projects.blender.org/blender/blender/pulls/135685
---
 build_files/cmake/macros.cmake | 8 +++++++-
 1 file changed, 7 insertions(+), 1 deletion(-)

diff --git a/build_files/cmake/macros.cmake b/build_files/cmake/macros.cmake
index bb5e66d75d1..7fcbfb1c7f0 100644
--- a/build_files/cmake/macros.cmake
+++ b/build_files/cmake/macros.cmake
@@ -572,7 +572,13 @@ macro(TEST_SSE_SUPPORT
     check_c_source_runs("
       #include <nmmintrin.h>
       #include <emmintrin.h>
-      int main(void) { __m128i v = _mm_setzero_si128(); v = _mm_cmpgt_epi64(v,v); return 0; }"
+      #include <smmintrin.h>
+      int main(void) {
+        __m128i v = _mm_setzero_si128();
+        v = _mm_cmpgt_epi64(v,v);
+        if (_mm_test_all_zeros(v, v)) return 0;
+        return 1;
+      }"
     SUPPORT_SSE42_BUILD)
   endif()