From c0da73e1b8e5933ca117512499ccac4e208bd8e0 Mon Sep 17 00:00:00 2001
From: Owen Taylor <otaylor@redhat.com>
Date: Sat, 27 Aug 2005 18:36:09 +0000
Subject: [PATCH] Make the code work with -fomit-frame-pointer by making sure
 that %esp isn't modified at the point where we access output operands.
 (#4269, Patch from Ronald Wahl)

---
 pixman/ChangeLog   |  7 +++++++
 pixman/src/fbmmx.c | 24 +++++++++++++++++-------
 2 files changed, 24 insertions(+), 7 deletions(-)

diff --git a/pixman/ChangeLog b/pixman/ChangeLog
index 0e9f96849..c4cd4c6dd 100644
--- a/pixman/ChangeLog
+++ b/pixman/ChangeLog
@@ -1,3 +1,10 @@
+2005-08-27  Owen Taylor  <otaylor@redhat.com>
+
+	* src/fbmmx.c (detectCPUFeatures): Make the code work with
+	-fomit-frame-pointer by making sure that %esp isn't modified at
+	the point where we access output operands. (#4269, Patch from
+	Ronald Wahl)
+	
 2005-08-22  Owen Taylor  <otaylor@redhat.com>
 
 	* src/pixregion.c (pixman_region_union_rect): When width/height
diff --git a/pixman/src/fbmmx.c b/pixman/src/fbmmx.c
index 42ba4162b..2523b622d 100644
--- a/pixman/src/fbmmx.c
+++ b/pixman/src/fbmmx.c
@@ -2488,28 +2488,38 @@ static unsigned int detectCPUFeatures(void) {
     vendor[0] = 0;
     vendor[12] = 0;
     /* see p. 118 of amd64 instruction set manual Vol3 */
-    __asm__ ("push %%ebx\n"
-             "pushf\n"
+    /* We need to be careful about the handling of %ebx and
+     * %esp here. We can't declare either one as clobbered
+     * since they are special registers (%ebx is the "PIC
+     * register" holding an offset to global data, %esp the
+     * stack pointer), so we need to make sure they have their
+     * original values when we access the output operands.
+     */
+    __asm__ ("pushf\n"
              "pop %%eax\n"
-             "mov %%eax, %%ebx\n"
+             "mov %%eax, %%ecx\n"
              "xor $0x00200000, %%eax\n"
              "push %%eax\n"
              "popf\n"
              "pushf\n"
              "pop %%eax\n"
              "mov $0x0, %%edx\n"
-             "xor %%ebx, %%eax\n"
+             "xor %%ecx, %%eax\n"
              "jz skip\n"
 
              "mov $0x00000000, %%eax\n"
+	     "push %%ebx\n"
              "cpuid\n"
-             "mov %%ebx, %1\n"
+             "mov %%ebx, %%eax\n"
+	     "pop %%ebx\n"
+             "mov %%eax, %1\n"
              "mov %%edx, %2\n"
              "mov %%ecx, %3\n"
              "mov $0x00000001, %%eax\n"
+	     "push %%ebx\n"
              "cpuid\n"
+	     "pop %%ebx\n"
              "skip:\n"
-             "pop %%ebx\n"
              "mov %%edx, %0\n"
              : "=r" (result), 
                "=m" (vendor[0]), 
@@ -2543,8 +2553,8 @@ static unsigned int detectCPUFeatures(void) {
                     "mov $0x80000001, %%eax\n"
                     "cpuid\n"
                     "skip2:\n"
-                    "mov %%edx, %0\n"
                     "pop %%ebx\n"
+                    "mov %%edx, %0\n"
                     : "=r" (result)
                     :
                     : "%eax", "%ecx", "%edx"