PPC: 32-bit asm for MAC64 and MLS64

GCC makes a mess of these operations, so give it a hand.

55% faster MP3 decoding on G4.

Originally committed as revision 18794 to svn://svn.ffmpeg.org/ffmpeg/trunk

libavcodec/ppc/mathops.h

@@ -44,4 +44,34 @@ static inline av_const int MULH(int a, int b){
     return r;
 }
 
+#if !HAVE_PPC64
+static inline av_const int64_t MAC64(int64_t d, int a, int b)
+{
+    union { uint64_t x; unsigned hl[2]; } x = { d };
+    int h, l;
+    __asm__ ("mullw %3, %4, %5   \n\t"
+             "mulhw %2, %4, %5   \n\t"
+             "addc  %1, %1, %3   \n\t"
+             "adde  %0, %0, %2   \n\t"
+             : "+r"(x.hl[0]), "+r"(x.hl[1]), "=&r"(h), "=&r"(l)
+             : "r"(a), "r"(b));
+    return x.x;
+}
+#define MAC64(d, a, b) ((d) = MAC64(d, a, b))
+
+static inline av_const int64_t MLS64(int64_t d, int a, int b)
+{
+    union { uint64_t x; unsigned hl[2]; } x = { d };
+    int h, l;
+    __asm__ ("mullw %3, %4, %5   \n\t"
+             "mulhw %2, %4, %5   \n\t"
+             "subfc %1, %3, %1   \n\t"
+             "subfe %0, %2, %0   \n\t"
+             : "+r"(x.hl[0]), "+r"(x.hl[1]), "=&r"(h), "=&r"(l)
+             : "r"(a), "r"(b));
+    return x.x;
+}
+#define MLS64(d, a, b) ((d) = MLS64(d, a, b))
+#endif
+
 #endif /* AVCODEC_PPC_MATHOPS_H */