Hack around gcc 4.6 breaking asm using call.
authorReimar Döffinger <Reimar.Doeffinger@gmx.de>
Sun, 28 Aug 2011 19:14:13 +0000 (21:14 +0200)
committerCarl Eugen Hoyos <cehoyos@ag.or.at>
Wed, 21 Sep 2011 21:50:05 +0000 (23:50 +0200)
gcc 4.6 no longer decrements esp to account for local variables.
Thus using call will end up overwriting some local variable.
So add an extra one it can safely clobber.
This is a huge hack because it's basically pure chance it works,
no idea how this is supposed to be done.

Fixes trac ticket #397.

Signed-off-by: Reimar Döffinger <Reimar.Doeffinger@gmx.de>
(cherry picked from commit c928e9172928f3cddab949b107dd53b6bf79555e)

libswscale/x86/swscale_template.c

index 25399fa..e715270 100644 (file)
@@ -2240,6 +2240,10 @@ static void RENAME(hyscale_fast)(SwsContext *c, int16_t *dst,
 #if defined(PIC)
     DECLARE_ALIGNED(8, uint64_t, ebxsave);
 #endif
+    // HACK: gcc 4.6 no longer decrements esp,
+    // use this to make it reserve space for the call
+    // return address
+    void *dummy;
 
     __asm__ volatile(
 #if defined(PIC)
@@ -2291,6 +2295,7 @@ static void RENAME(hyscale_fast)(SwsContext *c, int16_t *dst,
 #if defined(PIC)
           ,"m" (ebxsave)
 #endif
+          ,"m" (dummy)
         : "%"REG_a, "%"REG_c, "%"REG_d, "%"REG_S, "%"REG_D
 #if !defined(PIC)
          ,"%"REG_b
@@ -2312,6 +2317,10 @@ static void RENAME(hcscale_fast)(SwsContext *c, int16_t *dst1, int16_t *dst2,
 #if defined(PIC)
     DECLARE_ALIGNED(8, uint64_t, ebxsave);
 #endif
+    // HACK: gcc 4.6 no longer decrements esp,
+    // use this to make it reserve space for the call
+    // return address
+    void *dummy;
 
     __asm__ volatile(
 #if defined(PIC)
@@ -2351,6 +2360,7 @@ static void RENAME(hcscale_fast)(SwsContext *c, int16_t *dst1, int16_t *dst2,
 #if defined(PIC)
           ,"m" (ebxsave)
 #endif
+          ,"m" (dummy)
         : "%"REG_a, "%"REG_c, "%"REG_d, "%"REG_S, "%"REG_D
 #if !defined(PIC)
          ,"%"REG_b