On Sat, 29 Sep 2012 00:12:16 -0700
Matt Turner <matts...@gmail.com> wrote:
> Siarhei, can you measure any performance improvement with this? I
> can't... :(
I guess that's because you patched the code for the 8-bit
interpolation precision, and pixman is now using 7 bits by default.
But PMADDUBSW can be only used for the first step of interpolation
(vertical) and not the second one (horizontal). Because the first step
does 8-bit * 7-bit -> 15-bit multiplication. And the second step does
a wider 15-bit * 7-bit -> 22-bit multiplication.
The needed changes may look like this:
diff --git a/pixman/pixman-sse2.c b/pixman/pixman-sse2.c
index efed310..b260c95 100644
--- a/pixman/pixman-sse2.c
+++ b/pixman/pixman-sse2.c
@@ -32,6 +32,7 @@
#include <xmmintrin.h> /* for _mm_shuffle_pi16 and _MM_SHUFFLE */
#include <emmintrin.h> /* for SSE2 intrinsics */
+#include <tmmintrin.h> /* for SSSE3 intrinsics */
#include "pixman-private.h"
#include "pixman-combine32.h"
#include "pixman-inlines.h"
@@ -5401,15 +5402,14 @@ FAST_NEAREST_MAINLOOP_COMMON
(sse2_8888_n_8888_normal_OVER,
#define BMSK ((1 << BILINEAR_INTERPOLATION_BITS) - 1)
#define BILINEAR_DECLARE_VARIABLES
\
- const __m128i xmm_wt = _mm_set_epi16 (wt, wt, wt, wt, wt, wt, wt, wt);
\
- const __m128i xmm_wb = _mm_set_epi16 (wb, wb, wb, wb, wb, wb, wb, wb);
\
+ const __m128i xmm_wtb = _mm_set_epi8 (wt, wb, wt, wb, wt, wb, wt, wb,
\
+ wt, wb, wt, wb, wt, wb, wt, wb);
\
const __m128i xmm_xorc8 = _mm_set_epi16 (0, 0, 0, 0, BMSK, BMSK, BMSK,
BMSK);\
const __m128i xmm_addc8 = _mm_set_epi16 (0, 0, 0, 0, 1, 1, 1, 1);
\
const __m128i xmm_xorc7 = _mm_set_epi16 (0, BMSK, 0, BMSK, 0, BMSK, 0,
BMSK);\
const __m128i xmm_addc7 = _mm_set_epi16 (0, 1, 0, 1, 0, 1, 0, 1);
\
const __m128i xmm_ux = _mm_set_epi16 (unit_x, unit_x, unit_x, unit_x,
\
unit_x, unit_x, unit_x, unit_x);
\
- const __m128i xmm_zero = _mm_setzero_si128 ();
\
__m128i xmm_x = _mm_set_epi16 (vx, vx, vx, vx, vx, vx, vx, vx)
#define BILINEAR_INTERPOLATE_ONE_PIXEL(pix)
\
@@ -5422,10 +5422,7 @@ do {
\
(__m128i *)&src_bottom[pixman_fixed_to_int (vx)]);
\
vx += unit_x;
\
/* vertical interpolation */
\
- a = _mm_add_epi16 (_mm_mullo_epi16 (_mm_unpacklo_epi8 (tltr, xmm_zero),
\
- xmm_wt),
\
- _mm_mullo_epi16 (_mm_unpacklo_epi8 (blbr, xmm_zero),
\
- xmm_wb));
\
+ a = _mm_maddubs_epi16 (_mm_unpacklo_epi8 (blbr, tltr), xmm_wtb);
\
if (BILINEAR_INTERPOLATION_BITS < 8)
\
{
\
/* calculate horizontal weights */
\
And I'm getting the following performance improvement on Core i7 860
when running "lowlevel-blt-bench -b src_8888_8888":
before:
src_8888_8888 = L1: 318.11 L2: 314.48 M:311.16
after:
src_8888_8888 = L1: 356.75 L2: 352.18 M:348.76
That's just ~12% faster. The next step would be to try taking the
compiler out of the way and ensuring that no CPU cycles are wasted :)
--
Best regards,
Siarhei Siamashka
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