From 6e2b6f676c49f271b55f52dd35450d172ff8468c Mon Sep 17 00:00:00 2001 From: Daniel Pouzzner Date: Mon, 3 Aug 2026 22:29:42 -0500 Subject: [PATCH] m4/ax_linuxkm.m4: in the AX_SIMD_CC_COMPILER_FLAGS setup, drop the -mavx and -mavx2 AX_APPEND_COMPILE_FLAGS. gcc emits AVX instructions unbidden under those flags (e.g. for 128-bit types) in code paths that cannot be runtime-dispatched on cpuid, leading to invalid-opcode crashes on CPUs lacking AVX (e.g. Westmere). --- m4/ax_linuxkm.m4 | 5 +++-- 1 file changed, 3 insertions(+), 2 deletions(-) diff --git a/m4/ax_linuxkm.m4 b/m4/ax_linuxkm.m4 index 339386ea9e..39d4ac9bf6 100644 --- a/m4/ax_linuxkm.m4 +++ b/m4/ax_linuxkm.m4 @@ -77,8 +77,9 @@ AC_DEFUN([AX_SIMD_CC_COMPILER_FLAGS], [ AX_APPEND_COMPILE_FLAGS([-mmmx],[CFLAGS_SIMD_ENABLE]) AX_APPEND_COMPILE_FLAGS([-msse2],[CFLAGS_SIMD_ENABLE]) AX_APPEND_COMPILE_FLAGS([-msse4],[CFLAGS_SIMD_ENABLE]) - AX_APPEND_COMPILE_FLAGS([-mavx],[CFLAGS_SIMD_ENABLE]) - AX_APPEND_COMPILE_FLAGS([-mavx2],[CFLAGS_SIMD_ENABLE]) + # Don't add -mavx or -mavx2 -- gcc will emit AVX instructions unbidden, + # e.g. for 128 bit types, that can't be runtime-dispatched based on cpuid, leading + # to crashes (unknown opcodes) on CPUs lacking AVX. AX_APPEND_COMPILE_FLAGS([-mno-general-regs-only],[CFLAGS_SIMD_ENABLE]) fi