[Mesa-dev] [PATCH] mesa: Ensure stack is realigned on x86.

Jose Fonseca jfonseca at vmware.com
Tue Dec 2 12:27:38 PST 2014

From: José Fonseca <jfonseca at vmware.com>

Nowadays GCC assumes stack pointer is 16-byte aligned even on 32-bits,
but that is an assumption OpenGL drivers (or any dynamic library for
that matter) can affort to make as there are many closed- and open-
source application binaries out there that only assume 4-byte stack

This fix uses force_align_arg_pointer GCC attribute, and is only a
stop-gap measure.

The right fix would be to pass -mstackrealign or
-mincoming-stack-boundary=2 to all source fails that use any -msse*
option, as there is no way to guarantee if/when GCC will decide to spill
SSE registers to the stack.

 src/mesa/main/sse_minmax.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/src/mesa/main/sse_minmax.c b/src/mesa/main/sse_minmax.c
index 222ac14..93cf2a6 100644
--- a/src/mesa/main/sse_minmax.c
+++ b/src/mesa/main/sse_minmax.c
@@ -31,6 +31,9 @@
 #include <stdint.h>
+#if !defined(__x86_64__)
+   __attribute__((force_align_arg_pointer))
 _mesa_uint_array_min_max(const unsigned *ui_indices, unsigned *min_index,
                          unsigned *max_index, const unsigned count)

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