[libpng16] Backed out previous optimization; the compiler should handle that.

ANNOUNCE

@@ -45,9 +45,6 @@ Version 1.6.24beta02 [June 19, 2016]
     implemented in 1.7), however a simple safe fix here is to chose the lowest
     numbered filter in the list from png_set_filter (this only works if the
     first problem is also fixed) (John Bowler).
-  Avoid filter-selection heuristic sum calculations in cases where only one
-    filter is a candidate for selection. This trades off code size (added
-    png_setup_*_row_only() functions) for speed.
 
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CHANGES

@@ -5616,9 +5616,6 @@ Version 1.6.24beta02 [June 19, 2016]
     implemented in 1.7), however a simple safe fix here is to chose the lowest
     numbered filter in the list from png_set_filter (this only works if the
     first problem is also fixed) (John Bowler).
-  Avoid filter-selection heuristic sum calculations in cases where only one
-    filter is a candidate for selection. This trades off code size (added
-    png_setup_*_row_only() functions) for speed.
 
 Send comments/corrections/commendations to png-mng-implement at lists.sf.net
 (subscription required; visit

pngwutil.c

@@ -2278,28 +2278,6 @@ png_setup_sub_row(png_structrp png_ptr, const png_uint_32 bpp,
    return (sum);
 }
 
-static void /* PRIVATE */
-png_setup_sub_row_only(png_structrp png_ptr, const png_uint_32 bpp,
-    const png_size_t row_bytes)
-{
-   png_bytep rp, dp, lp;
-   png_size_t i;
-
-   png_ptr->try_row[0] = PNG_FILTER_VALUE_SUB;
-
-   for (i = 0, rp = png_ptr->row_buf + 1, dp = png_ptr->try_row + 1; i < bpp;
-        i++, rp++, dp++)
-   {
-      *dp = *rp;
-   }
-
-   for (lp = png_ptr->row_buf + 1; i < row_bytes;
-      i++, rp++, lp++, dp++)
-   {
-      *dp = (png_byte)(((int)*rp - (int)*lp) & 0xff);
-   }
-}
-
 static png_size_t /* PRIVATE */
 png_setup_up_row(png_structrp png_ptr, const png_size_t row_bytes,
     const png_size_t lmins)
@@ -2324,21 +2302,6 @@ png_setup_up_row(png_structrp png_ptr, const png_size_t row_bytes,
 
    return (sum);
 }
-static void /* PRIVATE */
-png_setup_up_row_only(png_structrp png_ptr, const png_size_t row_bytes)
-{
-   png_bytep rp, dp, pp;
-   png_size_t i;
-
-   png_ptr->try_row[0] = PNG_FILTER_VALUE_UP;
-
-   for (i = 0, rp = png_ptr->row_buf + 1, dp = png_ptr->try_row + 1,
-       pp = png_ptr->prev_row + 1; i < row_bytes;
-       i++, rp++, pp++, dp++)
-   {
-      *dp = (png_byte)(((int)*rp - (int)*pp) & 0xff);
-   }
-}
 
 static png_size_t /* PRIVATE */
 png_setup_avg_row(png_structrp png_ptr, const png_uint_32 bpp,
@@ -2372,27 +2335,6 @@ png_setup_avg_row(png_structrp png_ptr, const png_uint_32 bpp,
 
    return (sum);
 }
-static void /* PRIVATE */
-png_setup_avg_row_only(png_structrp png_ptr, const png_uint_32 bpp,
-      const png_size_t row_bytes)
-{
-   png_bytep rp, dp, pp, lp;
-   png_uint_32 i;
-
-   png_ptr->try_row[0] = PNG_FILTER_VALUE_AVG;
-
-   for (i = 0, rp = png_ptr->row_buf + 1, dp = png_ptr->try_row + 1,
-        pp = png_ptr->prev_row + 1; i < bpp; i++)
-   {
-      *dp++ = (png_byte)(((int)*rp++ - ((int)*pp++ / 2)) & 0xff);
-   }
-
-   for (lp = png_ptr->row_buf + 1; i < row_bytes; i++)
-   {
-      *dp++ = (png_byte)(((int)*rp++ - (((int)*pp++ + (int)*lp++) / 2))
-          & 0xff);
-   }
-}
 
 static png_size_t /* PRIVATE */
 png_setup_paeth_row(png_structrp png_ptr, const png_uint_32 bpp,
@@ -2447,48 +2389,6 @@ png_setup_paeth_row(png_structrp png_ptr, const png_uint_32 bpp,
 
    return (sum);
 }
-static void /* PRIVATE */
-png_setup_paeth_row_only(png_structrp png_ptr, const png_uint_32 bpp,
-    const png_size_t row_bytes)
-{
-   png_bytep rp, dp, pp, cp, lp;
-   png_size_t i;
-
-   png_ptr->try_row[0] = PNG_FILTER_VALUE_PAETH;
-
-   for (i = 0, rp = png_ptr->row_buf + 1, dp = png_ptr->try_row + 1,
-       pp = png_ptr->prev_row + 1; i < bpp; i++)
-   {
-      *dp++ = (png_byte)(((int)*rp++ - (int)*pp++) & 0xff);
-   }
-
-   for (lp = png_ptr->row_buf + 1, cp = png_ptr->prev_row + 1; i < row_bytes;
-        i++)
-   {
-      int a, b, c, pa, pb, pc, p;
-
-      b = *pp++;
-      c = *cp++;
-      a = *lp++;
-
-      p = b - c;
-      pc = a - c;
-
-#ifdef PNG_USE_ABS
-      pa = abs(p);
-      pb = abs(pc);
-      pc = abs(p + pc);
-#else
-      pa = p < 0 ? -p : p;
-      pb = pc < 0 ? -pc : pc;
-      pc = (p + pc) < 0 ? -(p + pc) : p + pc;
-#endif
-
-      p = (pa <= pb && pa <=pc) ? a : (pb <= pc) ? b : c;
-
-      *dp++ = (png_byte)(((int)*rp++ - p) & 0xff);
-   }
-}
 #endif /* WRITE_FILTER */
 
 void /* PRIVATE */
@@ -2576,7 +2476,10 @@ png_write_find_filter(png_structrp png_ptr, png_row_infop row_info)
    if (filter_to_do == PNG_FILTER_SUB)
    /* It's the only filter so no testing is needed */
    {
-      png_setup_sub_row_only(png_ptr, bpp, row_bytes);
+      /* Passing PNG_SIZE_MAX here and below prevents the 'setup' function
+       * breaking out of the loop when lmins is exceeded.
+       */
+      (void) png_setup_sub_row(png_ptr, bpp, row_bytes, PNG_SIZE_MAX);
       best_row = png_ptr->try_row;
    }
 
@@ -2602,7 +2505,7 @@ png_write_find_filter(png_structrp png_ptr, png_row_infop row_info)
    /* Up filter */
    if (filter_to_do == PNG_FILTER_UP)
    {
-      png_setup_up_row_only(png_ptr, row_bytes);
+      (void) png_setup_up_row(png_ptr, row_bytes, PNG_SIZE_MAX);
       best_row = png_ptr->try_row;
    }
 
@@ -2628,7 +2531,7 @@ png_write_find_filter(png_structrp png_ptr, png_row_infop row_info)
    /* Avg filter */
    if (filter_to_do == PNG_FILTER_AVG)
    {
-      png_setup_avg_row_only(png_ptr, bpp, row_bytes);
+      (void) png_setup_avg_row(png_ptr, bpp, row_bytes, PNG_SIZE_MAX);
       best_row = png_ptr->try_row;
    }
 
@@ -2654,7 +2557,7 @@ png_write_find_filter(png_structrp png_ptr, png_row_infop row_info)
    /* Paeth filter */
    if ((filter_to_do == PNG_FILTER_PAETH) != 0)
    {
-      png_setup_paeth_row_only(png_ptr, bpp, row_bytes);
+      (void) png_setup_paeth_row(png_ptr, bpp, row_bytes, PNG_SIZE_MAX);
       best_row = png_ptr->try_row;
    }