From 2040285ce94949e91d4df57973ecaded59db45d2 Mon Sep 17 00:00:00 2001 From: Pandora Date: Wed, 6 Dec 2017 13:57:07 -0500 Subject: [PATCH] revert back to better blurring behaviour --- blur.c | 159 ++++++++++++++--------------- blur.h | 14 +-- blur_simd.c | 276 +++++++-------------------------------------------- configure.ac | 4 +- 4 files changed, 119 insertions(+), 334 deletions(-) diff --git a/blur.c b/blur.c index 7509f3e..737ece1 100644 --- a/blur.c +++ b/blur.c @@ -1,6 +1,6 @@ /* - * Copyright © 2008 Kristian Høgsberg - * Copyright © 2009 Chris Wilson + * Copyright © 2008 Kristian Høgsberg + * Copyright © 2009 Chris Wilson * * Permission to use, copy, modify, distribute, and sell this software and its * documentation for any purpose is hereby granted without fee, provided that @@ -23,12 +23,9 @@ #include #include "blur.h" - -#define ARRAY_LENGTH(a) (sizeof (a) / sizeof (a)[0]) - -/* Performs a simple 2D Gaussian blur of radius @radius on surface @surface. */ +/* Performs a simple 2D Gaussian blur of standard devation @sigma surface @surface. */ void -blur_image_surface (cairo_surface_t *surface, int radius) +blur_image_surface (cairo_surface_t *surface, int sigma) { cairo_surface_t *tmp; int width, height; @@ -63,92 +60,86 @@ blur_image_surface (cairo_surface_t *surface, int radius) return; src = (uint32_t*)cairo_image_surface_get_data (surface); - dst = (uint32_t*)cairo_image_surface_get_data (tmp); - -#ifdef __SSE3__ - blur_impl_ssse3(src, dst, width, height, 4.5); -#elif __SSE2__ - blur_impl_sse2(src, dst, width, height, 4.5); + + // according to a paper by Peter Kovesi [1], box filter of width w, equals to Gaussian blur of following sigma: + // σ_av = sqrt((w*w-1)/12) + // for our 7x7 filter we have σ_av = 2.0. + // applying the same Gaussian filter n times results in σ_n = sqrt(n*σ_av*σ_av) [2] + // after some trivial math, we arrive at n = ((σ_d)/(σ_av))^2 + // since it's a box blur filter, n >= 3 + // + // [1]: http://www.peterkovesi.com/papers/FastGaussianSmoothing.pdf + // [2]: https://en.wikipedia.org/wiki/Gaussian_blur#Mathematics + + int n = lrintf((sigma*sigma)/(SIGMA_AV*SIGMA_AV)); + if (n < 3) n = 3; + + for (int i = 0; i < n; i++) + { + // horizontal pass includes image transposition: + // instead of writing pixel src[x] to dst[x], + // we write it to transposed location. + // (to be exact: dst[height * current_column + current_row]) +#ifdef __SSE2__ + blur_impl_horizontal_pass_sse2(src, dst, width, height); + blur_impl_horizontal_pass_sse2(dst, src, height, width); #else - int src_stride = cairo_image_surface_get_stride (surface); - int dst_stride = cairo_image_surface_get_stride (tmp); - blur_impl_naive(src, dst, width, height, src_stride, dst_stride, 10000); + blur_impl_horizontal_pass_generic(src, dst, width, height); + blur_impl_horizontal_pass_generic(dst, src, height, width); #endif + } + cairo_surface_destroy (tmp); cairo_surface_flush (surface); cairo_surface_mark_dirty (surface); } -void blur_impl_naive(uint32_t* _src, uint32_t* _dst, int width, int height, int src_stride, int dst_stride, int radius) -{ - int x, y, z, w; - uint32_t *s, *d, a, p; - int i, j, k; - uint8_t kernel[17]; - const int size = ARRAY_LENGTH (kernel); - const int half = size / 2; - - uint8_t *src = (uint8_t*)_src; - uint8_t *dst = (uint8_t*)_dst; - - a = 0; - for (i = 0; i < size; i++) { - double f = i - half; - a += kernel[i] = exp (- f * f / 30.0) * 80; - } - - /* Horizontally blur from surface -> tmp */ - for (i = 0; i < height; i++) { - s = (uint32_t *) (src + i * src_stride); - d = (uint32_t *) (dst + i * dst_stride); - for (j = 0; j < width; j++) { - if (radius < j && j < width - radius) { - d[j] = s[j]; - continue; - } - - x = y = z = w = 0; - for (k = 0; k < size; k++) { - if (j - half + k < 0 || j - half + k >= width) - continue; - - p = s[j - half + k]; - - x += ((p >> 24) & 0xff) * kernel[k]; - y += ((p >> 16) & 0xff) * kernel[k]; - z += ((p >> 8) & 0xff) * kernel[k]; - w += ((p >> 0) & 0xff) * kernel[k]; - } - d[j] = (x / a << 24) | (y / a << 16) | (z / a << 8) | w / a; - } - } - - /* Then vertically blur from tmp -> surface */ - for (i = 0; i < height; i++) { - s = (uint32_t *) (dst + i * dst_stride); - d = (uint32_t *) (src + i * src_stride); - for (j = 0; j < width; j++) { - if (radius <= i && i < height - radius) { - d[j] = s[j]; - continue; +void blur_impl_horizontal_pass_generic(uint32_t *src, uint32_t *dst, int width, int height) { + for (int row = 0; row < height; row++) { + for (int column = 0; column < width; column++, src++) { + uint32_t rgbaIn[KERNEL_SIZE]; + + // handle borders + int leftBorder = column < HALF_KERNEL; + int rightBorder = column > width - HALF_KERNEL; + int i = 0; + if (leftBorder) { + // for kernel size 7x7 and column == 0, we have: + // x x x P0 P1 P2 P3 + // first loop mirrors P{0..3} to fill x's, + // second one loads P{0..3} + for (; i < HALF_KERNEL - column; i++) + rgbaIn[i] = *(src + (HALF_KERNEL - i)); + for (; i < KERNEL_SIZE; i++) + rgbaIn[i] = *(src - (HALF_KERNEL - i)); + } else if (rightBorder) { + for (; i < width - column; i++) + rgbaIn[i] = *(src + i); + for (int k = 0; i < KERNEL_SIZE; i++, k++) + rgbaIn[i] = *(src - k); + } else { + for (; i < KERNEL_SIZE; i++) + rgbaIn[i] = *(src + i - HALF_KERNEL); + } + + uint32_t acc[4] = {0}; + + for (i = 0; i < KERNEL_SIZE; i++) { + acc[0] += (rgbaIn[i] & 0xFF000000) >> 24; + acc[1] += (rgbaIn[i] & 0x00FF0000) >> 16; + acc[2] += (rgbaIn[i] & 0x0000FF00) >> 8; + acc[3] += (rgbaIn[i] & 0x000000FF) >> 0; + } + + for(i = 0; i < 4; i++) + acc[i] *= 1.0/KERNEL_SIZE; + + *(dst + height * column + row) = (acc[0] << 24) | + (acc[1] << 16) | + (acc[2] << 8 ) | + (acc[3] << 0); } - - x = y = z = w = 0; - for (k = 0; k < size; k++) { - if (i - half + k < 0 || i - half + k >= height) - continue; - - s = (uint32_t *) (dst + (i - half + k) * dst_stride); - p = s[j]; - - x += ((p >> 24) & 0xff) * kernel[k]; - y += ((p >> 16) & 0xff) * kernel[k]; - z += ((p >> 8) & 0xff) * kernel[k]; - w += ((p >> 0) & 0xff) * kernel[k]; - } - d[j] = (x / a << 24) | (y / a << 16) | (z / a << 8) | w / a; - } } } diff --git a/blur.h b/blur.h index 478e2f0..fd93853 100644 --- a/blur.h +++ b/blur.h @@ -4,12 +4,14 @@ #include #include -void blur_image_surface (cairo_surface_t *surface, int radius); -void blur_impl_naive(uint32_t* src, uint32_t* dst, int width, int height, int src_stride, int dst_stride, int radius); -void blur_impl_sse2(uint32_t* src, uint32_t* dst, int width, int height, float sigma); -void blur_impl_horizontal_pass_sse2(uint32_t *src, uint32_t *dst, float *kernel, int width, int height); -void blur_impl_ssse3(uint32_t* src, uint32_t* dst, int width, int height, float sigma); -void blur_impl_horizontal_pass_ssse3(uint32_t *src, uint32_t *dst, int8_t *kernel, int width, int height); +#define KERNEL_SIZE 7 +#define SIGMA_AV 2 +#define HALF_KERNEL KERNEL_SIZE / 2 + +void blur_image_surface(cairo_surface_t *surface, int sigma); +void blur_impl_horizontal_pass_sse2(uint32_t *src, uint32_t *dst, int width, int height); +void blur_impl_horizontal_pass_generic(uint32_t *src, uint32_t *dst, int width, int height); #endif + diff --git a/blur_simd.c b/blur_simd.c index 9ee4abd..92aca9f 100644 --- a/blur_simd.c +++ b/blur_simd.c @@ -1,56 +1,19 @@ /* * vim:ts=4:sw=4:expandtab * - * © 2016 Sebastian Frysztak + * © 2016 Sebastian Frysztak * * See LICENSE for licensing information * */ #include "blur.h" -#include #include -#include -#include - -#define ALIGN16 __attribute__((aligned(16))) -#define KERNEL_SIZE 15 -#define HALF_KERNEL KERNEL_SIZE / 2 - -// number of xmm registers needed to store -// input pixels for given kernel size +// number of xmm registers needed to store input pixels for given kernel size #define REGISTERS_CNT (KERNEL_SIZE + 4/2) / 4 -// scaling factor for kernel coefficients. -// higher values cause desaturation. -// used in SSSE3 implementation. -#define SCALE_FACTOR 7 - -void blur_impl_sse2(uint32_t *src, uint32_t *dst, int width, int height, float sigma) { - // prepare kernel - float kernel[KERNEL_SIZE]; - float coeff = 1.0 / sqrtf(2 * M_PI * sigma * sigma), sum = 0; - - for (int i = 0; i < KERNEL_SIZE; i++) { - float x = HALF_KERNEL - i; - kernel[i] = coeff * expf(-x * x / (2.0 * sigma * sigma)); - sum += kernel[i]; - } - - // normalize kernel - for (int i = 0; i < KERNEL_SIZE; i++) - kernel[i] /= sum; - - // horizontal pass includes image transposition: - // instead of writing pixel src[x] to dst[x], - // we write it to transposed location. - // (to be exact: dst[height * current_column + current_row]) - blur_impl_horizontal_pass_sse2(src, dst, kernel, width, height); - blur_impl_horizontal_pass_sse2(dst, src, kernel, height, width); -} - -void blur_impl_horizontal_pass_sse2(uint32_t *src, uint32_t *dst, float *kernel, int width, int height) { +void blur_impl_horizontal_pass_sse2(uint32_t *src, uint32_t *dst, int width, int height) { uint32_t* o_src = src; for (int row = 0; row < height; row++) { for (int column = 0; column < width; column++, src++) { @@ -59,227 +22,58 @@ void blur_impl_horizontal_pass_sse2(uint32_t *src, uint32_t *dst, float *kernel, // handle borders int leftBorder = column < HALF_KERNEL; int rightBorder = column > width - HALF_KERNEL; - if (leftBorder || rightBorder) { - uint32_t _rgbaIn[KERNEL_SIZE + 1] ALIGN16; - int i = 0; - if (leftBorder) { - // for kernel size 7x7 and column == 0, we have: - // x x x P0 P1 P2 P3 - // first loop mirrors P{0..3} to fill x's, - // second one loads P{0..3} - for (; i < HALF_KERNEL - column; i++) - _rgbaIn[i] = *(src + (HALF_KERNEL - i)); - for (; i < KERNEL_SIZE; i++) - _rgbaIn[i] = *(src - (HALF_KERNEL - i)); - } else { - for (; i < width - column; i++) - _rgbaIn[i] = *(src + i); - for (int k = 0; i < KERNEL_SIZE; i++, k++) - _rgbaIn[i] = *(src - k); - } + uint32_t _rgbaIn[KERNEL_SIZE + 1] __attribute__((aligned(16))); + int i = 0; + if (leftBorder) { + // for kernel size 7x7 and column == 0, we have: + // x x x P0 P1 P2 P3 + // first loop mirrors P{0..3} to fill x's, + // second one loads P{0..3} + for (; i < HALF_KERNEL - column; i++) + _rgbaIn[i] = *(src + (HALF_KERNEL - i)); + for (; i < KERNEL_SIZE; i++) + _rgbaIn[i] = *(src - (HALF_KERNEL - i)); for (int k = 0; k < REGISTERS_CNT; k++) rgbaIn[k] = _mm_load_si128((__m128i*)(_rgbaIn + 4*k)); - } else { - for (int k = 0; k < REGISTERS_CNT; k++) { -#if 0 - printf("%p -> %p (%ld) || %p->%p\n", - o_src, - o_src + (height * width), - o_src + (height * width) - src, - src + 4*k - HALF_KERNEL, - ((__m128i*)src + 4*k - HALF_KERNEL) + 1 - ); -#endif - // if this copy would go out of bounds, break - if ((long long) (((__m128i*) src + 4*k - HALF_KERNEL) + 1) - > (long long) (o_src + (height * width))) - break; - rgbaIn[k] = _mm_loadu_si128((__m128i*)(src + 4*k - HALF_KERNEL)); - } - } - - // unpack each pixel, convert to float, - // multiply by corresponding kernel value - // and add to accumulator - __m128i tmp; - __m128i zero = _mm_setzero_si128(); - __m128 rgba_ps; - __m128 acc = _mm_setzero_ps(); - int counter = 0; - - for (int i = 0; i < 3; i++) - { - tmp = _mm_unpacklo_epi8(rgbaIn[i], zero); - rgba_ps = _mm_cvtepi32_ps(_mm_unpacklo_epi16(tmp, zero)); - acc = _mm_add_ps(acc, _mm_mul_ps(rgba_ps, _mm_set1_ps(kernel[counter++]))); - rgba_ps = _mm_cvtepi32_ps(_mm_unpackhi_epi16(tmp, zero)); - acc = _mm_add_ps(acc, _mm_mul_ps(rgba_ps, _mm_set1_ps(kernel[counter++]))); - - tmp = _mm_unpackhi_epi8(rgbaIn[i], zero); - rgba_ps = _mm_cvtepi32_ps(_mm_unpacklo_epi16(tmp, zero)); - acc = _mm_add_ps(acc, _mm_mul_ps(rgba_ps, _mm_set1_ps(kernel[counter++]))); - rgba_ps = _mm_cvtepi32_ps(_mm_unpackhi_epi16(tmp, zero)); - acc = _mm_add_ps(acc, _mm_mul_ps(rgba_ps, _mm_set1_ps(kernel[counter++]))); - } - - tmp = _mm_unpacklo_epi8(rgbaIn[3], zero); - rgba_ps = _mm_cvtepi32_ps(_mm_unpacklo_epi16(tmp, zero)); - acc = _mm_add_ps(acc, _mm_mul_ps(rgba_ps, _mm_set1_ps(kernel[counter++]))); - rgba_ps = _mm_cvtepi32_ps(_mm_unpackhi_epi16(tmp, zero)); - acc = _mm_add_ps(acc, _mm_mul_ps(rgba_ps, _mm_set1_ps(kernel[counter++]))); - - tmp = _mm_unpackhi_epi8(rgbaIn[3], zero); - rgba_ps = _mm_cvtepi32_ps(_mm_unpacklo_epi16(tmp, zero)); - acc = _mm_add_ps(acc, _mm_mul_ps(rgba_ps, _mm_set1_ps(kernel[counter++]))); - - __m128i rgbaOut = _mm_cvtps_epi32(acc); - rgbaOut = _mm_packs_epi32(rgbaOut, zero); - rgbaOut = _mm_packus_epi16(rgbaOut, zero); - *(dst + height * column + row) = _mm_cvtsi128_si32(rgbaOut); - } - } -} + } else if (rightBorder) { + for (; i < width - column; i++) + _rgbaIn[i] = *(src + i); + for (int k = 0; i < KERNEL_SIZE; i++, k++) + _rgbaIn[i] = *(src - k); -void blur_impl_ssse3(uint32_t *src, uint32_t *dst, int width, int height, float sigma) { - // prepare kernel - float kernelf[KERNEL_SIZE]; - int8_t kernel[KERNEL_SIZE + 1]; - float coeff = 1.0 / sqrtf(2 * M_PI * sigma * sigma), sum = 0; - - for (int i = 0; i < KERNEL_SIZE; i++) { - float x = HALF_KERNEL - i; - kernelf[i] = coeff * expf(-x * x / (2.0 * sigma * sigma)); - sum += kernelf[i]; - } - - // normalize kernel - for (int i = 0; i < KERNEL_SIZE; i++) - kernelf[i] /= sum; - - // round to nearest integer and convert to int - for (int i = 0; i < KERNEL_SIZE; i++) - kernel[i] = (int8_t)rintf(kernelf[i] * (1 << SCALE_FACTOR)); - kernel[KERNEL_SIZE] = 0; - - // horizontal pass includes image transposition: - // instead of writing pixel src[x] to dst[x], - // we write it to transposed location. - // (to be exact: dst[height * current_column + current_row]) - blur_impl_horizontal_pass_ssse3(src, dst, kernel, width, height); - blur_impl_horizontal_pass_ssse3(dst, src, kernel, height, width); -} - - -void blur_impl_horizontal_pass_ssse3(uint32_t *src, uint32_t *dst, int8_t *kernel, int width, int height) { - uint32_t* o_src = src; - __m128i _kern = _mm_loadu_si128((__m128i*)kernel); - __m128i rgbaIn[REGISTERS_CNT]; - - for (int row = 0; row < height; row++) { - for (int column = 0; column < width; column++, src++) { - uint32_t _rgbaIn[KERNEL_SIZE + 1] ALIGN16; -#if 0 - for (int j = 0; j < KERNEL_SIZE; ++j) { - printf("_rgbaIn[%d]: %p->%p\n", j, &_rgbaIn[j], &_rgbaIn[j] + 1); - } -#endif - // handle borders - int leftBorder = column < HALF_KERNEL; - int rightBorder = column > width - HALF_KERNEL; - if (leftBorder || rightBorder) { - int i = 0; - if (leftBorder) { - // for kernel size 7x7 and column == 0, we have: - // x x x P0 P1 P2 P3 - // first loop mirrors P{0..3} to fill x's, - // second one loads P{0..3} - for (; i < HALF_KERNEL - column; i++) - _rgbaIn[i] = *(src + (HALF_KERNEL - i)); - for (; i < KERNEL_SIZE; i++) - _rgbaIn[i] = *(src - (HALF_KERNEL - i)); - } else { - for (; i < width - column; i++) - _rgbaIn[i] = *(src + i); - for (int k = 0; i < KERNEL_SIZE; i++, k++) - _rgbaIn[i] = *(src - k); - } - - for (int k = 0; k < REGISTERS_CNT; k++) { -#if 0 - printf("K: %d; p: %p, p+4*k: %p, end of p: %p\n", k, _rgbaIn, _rgbaIn+4*k, ((__m128i*) (_rgbaIn +4*k)) + 1); -#endif + for (int k = 0; k < REGISTERS_CNT; k++) rgbaIn[k] = _mm_load_si128((__m128i*)(_rgbaIn + 4*k)); - } } else { for (int k = 0; k < REGISTERS_CNT; k++) { - if ((long long) (((__m128i*) src + 4*k - HALF_KERNEL) + 1) + if ((long long) (((__m128i*) src + 4*k - HALF_KERNEL) + 1) > (long long) (o_src + (height * width))) break; -#if 0 - printf("K: %d; p: %p -> %p\n", k, src+4*k - HALF_KERNEL, ((__m128i*) (src +4*k - HALF_KERNEL)) + 1); - printf("%p->%p, %p->%p (%ld)\n", (__m128i*) src + 4*k - HALF_KERNEL, ((__m128i*) src + 4*k - HALF_KERNEL) + 1, o_src, o_src + (width * height), o_src + (width * height) - src); -#endif rgbaIn[k] = _mm_loadu_si128((__m128i*)(src + 4*k - HALF_KERNEL)); } } - // basis of this implementation is _mm_maddubs_epi16 (aka pmaddubsw). - // 'rgba' holds 16 unsigned bytes, so 4 pixels. - // 'kern' holds 16 signed bytes kernel values multiplied by (1 << SCALE_FACTOR). - // before multiplication takes place, vectors need to be prepared: - // 'rgba' is shuffled from R1B1G1A1...R4B4G4A4 to R1R2R3R4...A1A2A3A4 - // 'kern' is shuffled from w1w2w3w4...w13w14w15w16 to w1w2w3w4 repeated 4 times - // then we call _mm_maddubs_epi16 and we get: - // -------------------------------------------------------------------------------------- - // | R1*w1 + R2*w2 | R3*w3 + R4*w4 | G1*w1 + G2*w2 | G3*w3 + G4*w4 | repeat for B and A | - // -------------------------------------------------------------------------------------- - // each 'rectangle' is a 16-byte signed int. - // then we repeat the process for the rest of input pixels, - // call _mm_hadds_epi16 to add adjacent ints and shift right to scale by SCALE_FACTOR. - - __m128i rgba, kern; __m128i zero = _mm_setzero_si128(); __m128i acc = _mm_setzero_si128(); - const __m128i rgba_shuf_mask = _mm_setr_epi8(0, 4, 8, 12, - 1, 5, 9, 13, - 2, 6, 10, 14, - 3, 7, 11, 15); - - const __m128i kern_shuf_mask = _mm_setr_epi8(0, 1, 2, 3, - 0, 1, 2, 3, - 0, 1, 2, 3, - 0, 1, 2, 3); - - rgba = _mm_shuffle_epi8(rgbaIn[0], rgba_shuf_mask); - kern = _mm_shuffle_epi8(_kern, kern_shuf_mask); - acc = _mm_adds_epi16(acc, _mm_maddubs_epi16(rgba, kern)); + acc = _mm_add_epi16(acc, _mm_unpacklo_epi8(rgbaIn[0], zero)); + acc = _mm_add_epi16(acc, _mm_unpackhi_epi8(rgbaIn[0], zero)); + acc = _mm_add_epi16(acc, _mm_unpacklo_epi8(rgbaIn[1], zero)); - rgba = _mm_shuffle_epi8(rgbaIn[1], rgba_shuf_mask); - kern = _mm_shuffle_epi8(_mm_srli_si128(_kern, 4), kern_shuf_mask); - acc = _mm_adds_epi16(acc, _mm_maddubs_epi16(rgba, kern)); + // kernel size equals to 7, but we can only load multiples of 4 pixels + // we have to set 8th pixel to zero + acc = _mm_add_epi16(acc, _mm_andnot_si128(_mm_set_epi32(0xFFFFFFFF, 0xFFFFFFFF, 0, 0), + _mm_unpackhi_epi8(rgbaIn[1], zero))); + acc = _mm_add_epi32(_mm_unpacklo_epi16(acc, zero), + _mm_unpackhi_epi16(acc, zero)); - rgba = _mm_shuffle_epi8(rgbaIn[2], rgba_shuf_mask); - kern = _mm_shuffle_epi8(_mm_srli_si128(_kern, 8), kern_shuf_mask); - acc = _mm_adds_epi16(acc, _mm_maddubs_epi16(rgba, kern)); + // multiplication is significantly faster than division + acc = _mm_cvtps_epi32(_mm_mul_ps(_mm_cvtepi32_ps(acc), + _mm_set1_ps(1.0/KERNEL_SIZE))); - rgba = _mm_shuffle_epi8(rgbaIn[3], rgba_shuf_mask); - kern = _mm_shuffle_epi8(_mm_srli_si128(_kern, 12), kern_shuf_mask); - acc = _mm_adds_epi16(acc, _mm_maddubs_epi16(rgba, kern)); - - acc = _mm_hadds_epi16(acc, zero); - acc = _mm_srai_epi16(acc, SCALE_FACTOR); - - // Cairo sets alpha channel to 255 - // (or -1, depending how you look at it) - // this quickly overflows accumulator, - // and alpha is calculated completely wrong. - // I assume most people don't use semi-transparent - // lock screen images, so no one will mind if we - // 'correct it' by setting alpha to 255. *(dst + height * column + row) = - _mm_cvtsi128_si32(_mm_packus_epi16(acc, zero)) | 0xFF000000; + _mm_cvtsi128_si32(_mm_packus_epi16(_mm_packs_epi32(acc, zero), zero)); } } } + diff --git a/configure.ac b/configure.ac index 5efbfcd..bef332d 100644 --- a/configure.ac +++ b/configure.ac @@ -101,10 +101,8 @@ AC_PROG_LN_S AM_PROG_AR AX_FLAGS_WARN_ALL -AX_APPEND_FLAG([-march=native], [AM_CFLAGS]) - AX_APPEND_FLAG([-O2], [AM_CFLAGS]) +AX_APPEND_FLAG([-O2], [AM_CFLAGS]) AX_APPEND_FLAG([-funroll-loops], [AM_CFLAGS]) -AX_APPEND_FLAG([-std=gnu99], [AM_CFLAGS]) AX_CHECK_COMPILE_FLAG([-Wunused-value], [AX_APPEND_FLAG([-Wunused-value], [AM_CFLAGS])]) AC_SUBST(AM_CFLAGS)