[libpng16] Added Intel SSE support (Matt Sarrett, Google Inc.)

1 files changed, 45 insertions, 0 deletions

diff --git a/contrib/intel/intel_init.c b/contrib/intel/intel_init.c
new file mode 100644
index 000000000..394984e06
--- /dev/null
+++ b/contrib/intel/intel_init.c
@@ -0,0 +1,45 @@
+
+/* intel_init.c - SSE2 optimized filter functions
+ *
+ * Copyright (c) 2016 Google, Inc.
+ *
+ * This code is released under the libpng license.
+ * For conditions of distribution and use, see the disclaimer
+ * and license in png.h
+ */
+
+#include "../pngpriv.h"
+
+#ifdef PNG_READ_SUPPORTED
+#if PNG_INTEL_SSE_IMPLEMENTATION > 0
+
+void
+png_init_filter_functions_sse2(png_structp pp, unsigned int bpp)
+{
+   // The techniques used to implement each of these filters in SSE operate on
+   // one pixel at a time.
+   // So they generally speed up 3bpp images about 3x, 4bpp images about 4x.
+   // They can scale up to 6 and 8 bpp images and down to 2 bpp images, 
+   // but they'd not likely have any benefit for 1bpp images.
+   // Most of these can be implemented using only MMX and 64-bit registers,
+   // but they end up a bit slower than using the equally-ubiquitous SSE2.
+   if (bpp == 3)
+   {
+      pp->read_filter[PNG_FILTER_VALUE_SUB-1] = png_read_filter_row_sub3_sse2;
+      pp->read_filter[PNG_FILTER_VALUE_AVG-1] = png_read_filter_row_avg3_sse2;
+      pp->read_filter[PNG_FILTER_VALUE_PAETH-1] =
+         png_read_filter_row_paeth3_sse2;
+   }
+   else if (bpp == 4)
+   {
+      pp->read_filter[PNG_FILTER_VALUE_SUB-1] = png_read_filter_row_sub4_sse2;
+      pp->read_filter[PNG_FILTER_VALUE_AVG-1] = png_read_filter_row_avg4_sse2;
+      pp->read_filter[PNG_FILTER_VALUE_PAETH-1] =
+          png_read_filter_row_paeth4_sse2;
+   }
+
+   // No need optimize PNG_FILTER_VALUE_UP.  The compiler should autovectorize.
+}
+
+#endif /* PNG_INTEL_SSE_IMPLEMENTATION > 0 */
+#endif /* PNG_READ_SUPPORTED */