Work around GCC bug causing crashes in Mozilla with SSE2

When using SSE2 intrinsics, gcc assumes that the stack is 16 byte
aligned. Unfortunately some code, such as Mozilla and Mono contain
code that aligns the stack to 4 bytes.

The __force_align_arg_pointer__ makes gcc generate a prologue that
realigns the stack pointer to 16 bytes.  Fix bug 15693.

diff --git a/configure.ac b/configure.ac
index d80022b..988bee1 100644 (file)
--- a/configure.ac
+++ b/configure.ac
@@ -213,8 +213,8 @@ xserver_save_CFLAGS=$CFLAGS
 CFLAGS="$CFLAGS -msse2 $SSE_CFLAGS"
 
 AC_COMPILE_IFELSE([
-#if defined(__GNUC__) && (__GNUC__ < 3 || (__GNUC__ == 3 && __GNUC_MINOR__ < 4))
-#error "Need GCC >= 3.4 for SSE2 intrinsics"
+#if defined(__GNUC__) && (__GNUC__ < 4 || (__GNUC__ == 4 && __GNUC_MINOR__ < 2))
+#error "Need GCC >= 4.2 for SSE2 intrinsics"
 #endif
 #include <mmintrin.h>
 #include <xmmintrin.h>

diff --git a/pixman/pixman-pict.c b/pixman/pixman-pict.c
index 00ac511..833d65a 100644 (file)
--- a/pixman/pixman-pict.c
+++ b/pixman/pixman-pict.c
@@ -1715,7 +1715,23 @@ pixman_optimize_operator(pixman_op_t op, pixman_image_t *pSrc, pixman_image_t *p
 
 }
 
+#if defined(USE_SSE2) && defined (__GNUC__)
 
+/*
+ * Work around GCC bug causing crashes in Mozilla with SSE2
+ * 
+ * When using SSE2 intrinsics, gcc assumes that the stack is 16 byte
+ * aligned. Unfortunately some code, such as Mozilla and Mono contain
+ * code that aligns the stack to 4 bytes.
+ *
+ * The __force_align_arg_pointer__ makes gcc generate a prologue that
+ * realigns the stack pointer to 16 bytes.
+ *
+ * See https://bugs.freedesktop.org/show_bug.cgi?id=15693
+ */
+
+__attribute__((__force_align_arg_pointer__))
+#endif
 void
 pixman_image_composite (pixman_op_t      op,
                        pixman_image_t * pSrc,