From 98fdfa99704f1cfef3d3a26c580b92749b6b64cb Mon Sep 17 00:00:00 2001 From: Janne Grunau Date: Thu, 13 Feb 2014 12:27:17 +0100 Subject: [PATCH] ppc: reduce overreads when loading 8 pixels in altivec dsp functions Altivec can only load naturally aligned vectors. To handle possibly unaligned data a second vector is loaded from an offset of the original location and the data is recovered through a vector permutation. Overreads are minimal if the offset for second load points to the last element of data. This is 7 for loading eight 8-bit pixels and overreads are reduced from 16 bytes to 8 bytes if the pixels are 64-bit aligned. For unaligned pixels the overread is reduced from 23 bytes to 15 bytes in the worst case. --- libavcodec/ppc/dsputil_altivec.c | 20 ++++++++++---------- 1 file changed, 10 insertions(+), 10 deletions(-) diff --git a/libavcodec/ppc/dsputil_altivec.c b/libavcodec/ppc/dsputil_altivec.c index f90ec74577..6f6c5f31fe 100644 --- a/libavcodec/ppc/dsputil_altivec.c +++ b/libavcodec/ppc/dsputil_altivec.c @@ -285,10 +285,10 @@ static int sad8_altivec(void *v, uint8_t *pix1, uint8_t *pix2, int line_size, in /* Read potentially unaligned pixels into t1 and t2 Since we're reading 16 pixels, and actually only want 8, mask out the last 8 pixels. The 0s don't change the sum. */ - vector unsigned char pix1l = vec_ld( 0, pix1); - vector unsigned char pix1r = vec_ld(15, pix1); - vector unsigned char pix2l = vec_ld( 0, pix2); - vector unsigned char pix2r = vec_ld(15, pix2); + vector unsigned char pix1l = vec_ld(0, pix1); + vector unsigned char pix1r = vec_ld(7, pix1); + vector unsigned char pix2l = vec_ld(0, pix2); + vector unsigned char pix2r = vec_ld(7, pix2); t1 = vec_and(vec_perm(pix1l, pix1r, perm1), permclear); t2 = vec_and(vec_perm(pix2l, pix2r, perm2), permclear); @@ -367,10 +367,10 @@ static int sse8_altivec(void *v, uint8_t *pix1, uint8_t *pix2, int line_size, in /* Read potentially unaligned pixels into t1 and t2 Since we're reading 16 pixels, and actually only want 8, mask out the last 8 pixels. The 0s don't change the sum. */ - vector unsigned char pix1l = vec_ld( 0, pix1); - vector unsigned char pix1r = vec_ld(15, pix1); - vector unsigned char pix2l = vec_ld( 0, pix2); - vector unsigned char pix2r = vec_ld(15, pix2); + vector unsigned char pix1l = vec_ld(0, pix1); + vector unsigned char pix1r = vec_ld(7, pix1); + vector unsigned char pix2l = vec_ld(0, pix2); + vector unsigned char pix2r = vec_ld(7, pix2); t1 = vec_and(vec_perm(pix1l, pix1r, perm1), permclear); t2 = vec_and(vec_perm(pix2l, pix2r, perm2), permclear); @@ -489,8 +489,8 @@ static void get_pixels_altivec(int16_t *restrict block, const uint8_t *pixels, i // Read potentially unaligned pixels. // We're reading 16 pixels, and actually only want 8, // but we simply ignore the extras. - vector unsigned char pixl = vec_ld( 0, pixels); - vector unsigned char pixr = vec_ld(15, pixels); + vector unsigned char pixl = vec_ld(0, pixels); + vector unsigned char pixr = vec_ld(7, pixels); bytes = vec_perm(pixl, pixr, perm); // convert the bytes into shorts