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)
committerReimar Döffinger <Reimar.Doeffinger@gmx.de>
Tue, 20 Sep 2011 17:05:51 +0000 (19:05 +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>
libswscale/x86/swscale_template.c

index 35839be..6a143f7 100644 (file)
@@ -1963,6 +1963,10 @@ 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)
@@ -2014,6 +2018,7 @@ 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
@@ -2035,6 +2040,10 @@ 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)
@@ -2074,6 +2083,7 @@ 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