shithub: opus

Info  •  Files  •  Log  •  Branches

optimisation: changed some for() loops to do-while() to give the compiler
a hint that there has to be at least one iteration.

--- a/libcelt/rate.c

+++ b/libcelt/rate.c

@@ -1,4 +1,4 @@

-/* (C) 2007 Jean-Marc Valin, CSIRO

+/* (C) 2007-2008 Jean-Marc Valin, CSIRO

 */

 /*

    Redistribution and use in source and binary forms, with or without

@@ -165,6 +165,7 @@

    for (i=0;i<LOG_MAX_PULSES;i++)

    {

       int mid = (lo+hi)>>1;

+      /* OPT: Make sure this is implemented with a conditional move */

       if (m->bits[band][mid] >= bits)

          hi = mid;

       else

--- a/libcelt/rate.h

+++ b/libcelt/rate.h

@@ -1,4 +1,4 @@

-/* (C) 2007 Jean-Marc Valin, CSIRO

+/* (C) 2007-2008 Jean-Marc Valin, CSIRO

 */

 /*

    Redistribution and use in source and binary forms, with or without

--- a/libcelt/vq.c

+++ b/libcelt/vq.c

@@ -157,8 +157,9 @@

       /* Choose between fast and accurate strategy depending on where we are in the search */

       if (pulsesLeft>1)

       {

-         for (j=0;j<N;j++)

-         {

+         /* OPT: This loop is very CPU-intensive */

+         j=0;

+         do {

             celt_word32_t num;

             celt_word16_t den;

             /* Select sign based on X[j] alone */

@@ -173,6 +174,7 @@

             den = ROUND16(Ryy,14);

             /* The idea is to check for num/den >= best_num/best_den, but that way

                we can do it without any division */

+            /* OPT: Make sure to use a conditional move here */

             if (MULT16_32_Q15(best_den, num) > MULT16_32_Q15(den, best_num))

             {

                best_den = den;

@@ -179,7 +181,7 @@

                best_num = num;

                best_id = j;

             }

-         }

+         } while (++j<N); /* Promises we loop at least once */

       } else {

          for (j=0;j<N;j++)

          {

@@ -275,17 +277,18 @@

       celt_word32_t xy=0, yy=0;

       celt_word32_t num;

       celt_word16_t den;

-      /* If this doesn't generate a double-MAC on supported architectures, 

+      /* OPT: If this doesn't generate a double-MAC (on supported architectures),

          complain to your compilor vendor */

-      for (j=0;j<N;j++)

-      {

+      j=0;

+      do {

          xy = MAC16_16(xy, x[j], Y[i+N-j-1]);

          yy = MAC16_16(yy, Y[i+N-j-1], Y[i+N-j-1]);

-      }

+      } while (++j<N); /* Promises we loop at least once */

       /* Using xy^2/yy as the score but without having to do the division */

       num = MULT16_16(ROUND16(xy,14),ROUND16(xy,14));

       den = ROUND16(yy,14);

       /* If you're really desperate for speed, just use xy as the score */

+      /* OPT: Make sure to use a conditional move here */

       if (MULT16_32_Q15(best_den, num) >  MULT16_32_Q15(den, best_num))

       {

          best_num = num;