diff --git a/libavcodec/x86/mathops.h b/libavcodec/x86/mathops.h
index 5949dfe..29ea584 100644
--- a/libavcodec/x86/mathops.h
+++ b/libavcodec/x86/mathops.h
@@ -28,10 +28,18 @@
 #if ARCH_X86_32
 #define MULL(ra, rb, shift) \
         ({ int rt, dummy; __asm__ (\
+    if (__builtin_constant_p(shift))
             "imull %3               \n\t"\
             "shrdl %4, %%edx, %%eax \n\t"\
             : "=a"(rt), "=d"(dummy)\
-            : "a" ((int)(ra)), "rm" ((int)(rb)), "i"(shift));\
+            :"a"(a), "rm"(b), "i"(shift & 0x1F)
+    else
+        __asm__ (
+            "imull %3               \n\t"
+            "shrdl %4, %%edx, %%eax \n\t"
+            :"=a"(rt), "=d"(dummy)
+            :"a"(a), "rm"(b), "c"((uint8_t)shift)
+        );
          rt; })
 
 #define MULH(ra, rb) \
@@ -81,19 +89,31 @@ __asm__ volatile(\
 // avoid +32 for shift optimization (gcc should do that ...)
 #define NEG_SSR32 NEG_SSR32
 static inline  int32_t NEG_SSR32( int32_t a, int8_t s){
+    if (__builtin_constant_p(s))
     __asm__ ("sarl %1, %0\n\t"
          : "+r" (a)
-         : "ic" ((uint8_t)(-s))
+         : "i" (-s & 0x1F)
     );
+    else
+        __asm__ ("sarl %1, %0\n\t"
+               : "+r" (a)
+               : "c" ((uint8_t)(-s))
+        );
     return a;
 }
 
 #define NEG_USR32 NEG_USR32
 static inline uint32_t NEG_USR32(uint32_t a, int8_t s){
+    if (__builtin_constant_p(s))
     __asm__ ("shrl %1, %0\n\t"
          : "+r" (a)
-         : "ic" ((uint8_t)(-s))
+         : "i" (-s & 0x1F)
     );
+    else
+        __asm__ ("shrl %1, %0\n\t"
+               : "+r" (a)
+               : "c" ((uint8_t)(-s))
+        );
     return a;
 }