x86: Disable AVX support on 64-bit MinGW

GCC for 64-bit Windows has a bug that it fails to properly re-align the stack pointer for use with 256-bit memory addresses (AVX). Therefore, there's about a 50/50 chance that any function using AVX will have an improperly-aligned stack. In release mode, stack accesses should be rare, but in debug mode they happen frequently. Either way, this is a ticking time bomb, so we disable. Clang is not affected. 32-bit MinGW is not affected. 64-bit in other OSes with GCC are not affected. Fixes: QTBUG-73539 Change-Id: Id061f35c088044b69a15fffd1580967808f31671 Reviewed-by: Allan Sandfeld Jensen <[email protected]>
redshiftzero · Feb 6, 2019 · 37352b2 · 37352b2
1 parent b319d14
commit 37352b2
Showing 1 changed file with 3 additions and 0 deletions.
diff --git a/config.tests/x86_simd/main.cpp b/config.tests/x86_simd/main.cpp
@@ -144,6 +144,9 @@ attribute_target("sha") void test_shani()
 #endif
 
 #if T(AVX)
+#  if defined(__WIN64__) && defined(__GNUC__) && !defined(__clang__)
+#    error "AVX support is broken in 64-bit MinGW - https://gcc.gnu.org/bugzilla/show_bug.cgi?id=49001"
+#  endif
 attribute_target("avx") void test_avx()
 {
     __m256d a = _mm256_setzero_pd();