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Unroll the multiply-add loops. At the cost of a function pointer dereference we get a whole lot of conditionals eliminated. Should be a solid win once the debug asserts are gone.

pull/32/head
Jorge Rodriguez 2014-07-26 12:04:39 -07:00
parent 7abd4ccf34
commit a95da9ee1d
1 changed files with 90 additions and 24 deletions
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114
stb_resample.h
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@ -490,9 +490,84 @@ static float* stbr__add_empty_ring_buffer_entry(stbr__info* stbr_info, int n)
return ring_buffer;
}
typedef void(*stbr__output_decode_coefficients)(float* output_buffer, int out_texel_index, float* decode_buffer, int decode_texel_index, int channels, float coefficient);
static void stbr__output_decode_coefficients_1(float* output_buffer, int out_texel_index, float* input_buffer, int input_texel_index, int channels, float coefficient)
{
STBR_DEBUG_ASSERT(channels == 1);
output_buffer[out_texel_index] += input_buffer[input_texel_index] * coefficient;
STBR_DEBUG_ASSERT(output_buffer[out_texel_index] <= 1.0f);
}
static void stbr__output_decode_coefficients_2(float* output_buffer, int out_texel_index, float* input_buffer, int input_texel_index, int channels, float coefficient)
{
STBR_DEBUG_ASSERT(channels == 2);
output_buffer[out_texel_index ] += input_buffer[input_texel_index ] * coefficient;
output_buffer[out_texel_index + 1] += input_buffer[input_texel_index + 1] * coefficient;
STBR_DEBUG_ASSERT(output_buffer[out_texel_index ] <= 1.0f);
STBR_DEBUG_ASSERT(output_buffer[out_texel_index+1] <= 1.0f);
}
static void stbr__output_decode_coefficients_3(float* output_buffer, int out_texel_index, float* input_buffer, int input_texel_index, int channels, float coefficient)
{
STBR_DEBUG_ASSERT(channels == 3);
output_buffer[out_texel_index ] += input_buffer[input_texel_index ] * coefficient;
output_buffer[out_texel_index + 1] += input_buffer[input_texel_index + 1] * coefficient;
output_buffer[out_texel_index + 2] += input_buffer[input_texel_index + 2] * coefficient;
STBR_DEBUG_ASSERT(output_buffer[out_texel_index ] <= 1.0f);
STBR_DEBUG_ASSERT(output_buffer[out_texel_index + 1] <= 1.0f);
STBR_DEBUG_ASSERT(output_buffer[out_texel_index + 2] <= 1.0f);
}
static void stbr__output_decode_coefficients_4(float* output_buffer, int out_texel_index, float* input_buffer, int input_texel_index, int channels, float coefficient)
{
STBR_DEBUG_ASSERT(channels == 4);
output_buffer[out_texel_index ] += input_buffer[input_texel_index ] * coefficient;
output_buffer[out_texel_index + 1] += input_buffer[input_texel_index + 1] * coefficient;
output_buffer[out_texel_index + 2] += input_buffer[input_texel_index + 2] * coefficient;
output_buffer[out_texel_index + 3] += input_buffer[input_texel_index + 3] * coefficient;
STBR_DEBUG_ASSERT(output_buffer[out_texel_index ] <= 1.0f);
STBR_DEBUG_ASSERT(output_buffer[out_texel_index + 1] <= 1.0f);
STBR_DEBUG_ASSERT(output_buffer[out_texel_index + 2] <= 1.0f);
STBR_DEBUG_ASSERT(output_buffer[out_texel_index + 3] <= 1.0f);
}
static void stbr__output_decode_coefficients_n(float* output_buffer, int out_texel_index, float* input_buffer, int input_texel_index, int channels, float coefficient)
{
int c;
for (c = 0; c < channels; c++)
{
output_buffer[out_texel_index + c] += input_buffer[input_texel_index + c] * coefficient;
STBR_DEBUG_ASSERT(output_buffer[out_texel_index + c] <= 1.0f);
}
}
static stbr__output_decode_coefficients stbr__get_output_decode_coefficients_function(int channels)
{
if (channels == 1)
return &stbr__output_decode_coefficients_1;
else if (channels == 2)
return &stbr__output_decode_coefficients_2;
else if (channels == 3)
return &stbr__output_decode_coefficients_3;
else if (channels == 4)
return &stbr__output_decode_coefficients_4;
return &stbr__output_decode_coefficients_n;
}
static void stbr__resample_horizontal_upsample(stbr__info* stbr_info, int n, float* output_buffer)
{
int x, k, c;
int x, k;
int output_w = stbr_info->output_w;
int kernel_texel_width = stbr__get_filter_texel_width(stbr_info->filter);
int channels = stbr_info->channels;
@ -500,6 +575,8 @@ static void stbr__resample_horizontal_upsample(stbr__info* stbr_info, int n, flo
stbr__contributors* horizontal_contributors = stbr_info->horizontal_contributors;
float* horizontal_coefficients = stbr_info->horizontal_coefficients;
stbr__output_decode_coefficients output_decode_coefficients_fn = stbr__get_output_decode_coefficients_function(channels);
for (x = 0; x < output_w; x++)
{
int n0 = horizontal_contributors[x].n0;
@ -521,19 +598,14 @@ static void stbr__resample_horizontal_upsample(stbr__info* stbr_info, int n, flo
int in_texel_index = k * channels;
float coefficient = horizontal_coefficients[coefficient_index];
for (c = 0; c < channels; c++)
{
output_buffer[out_texel_index + c] += decode_buffer[in_texel_index + c] * coefficient;
STBR_DEBUG_ASSERT(output_buffer[out_texel_index + c] <= 1.0f);
}
output_decode_coefficients_fn(output_buffer, out_texel_index, decode_buffer, in_texel_index, channels, coefficient);
}
}
}
static void stbr__resample_horizontal_downsample(stbr__info* stbr_info, int n, float* output_buffer)
{
int x, k, c;
int x, k;
int input_w = stbr_info->input_w;
int output_w = stbr_info->output_w;
int kernel_texel_width = stbr__get_filter_texel_width(stbr_info->filter);
@ -544,6 +616,8 @@ static void stbr__resample_horizontal_downsample(stbr__info* stbr_info, int n, f
int filter_texel_margin = stbr__get_filter_texel_margin(stbr_info->filter);
int max_x = input_w + filter_texel_margin * 2;
stbr__output_decode_coefficients output_decode_coefficients_fn = stbr__get_output_decode_coefficients_function(channels);
STBR_DEBUG_ASSERT(!stbr__use_width_upsampling(stbr_info));
for (x = 0; x < max_x; x++)
@ -565,12 +639,7 @@ static void stbr__resample_horizontal_downsample(stbr__info* stbr_info, int n, f
int out_texel_index = k * channels;
float coefficient = horizontal_coefficients[coefficient_index];
for (c = 0; c < channels; c++)
{
output_buffer[out_texel_index + c] += decode_buffer[in_texel_index + c] * coefficient;
STBR_DEBUG_ASSERT(output_buffer[out_texel_index + c] <= 1.0); // This would indicate that the sum of kernels for this texel doesn't add to 1.
}
output_decode_coefficients_fn(output_buffer, out_texel_index, decode_buffer, in_texel_index, channels, coefficient);
}
}
}
@ -638,6 +707,8 @@ static void stbr__resample_vertical_upsample(stbr__info* stbr_info, int n, int i
int output_row_index = n * stbr_info->output_stride_bytes;
stbr__output_decode_coefficients output_decode_coefficients_fn = stbr__get_output_decode_coefficients_function(channels);
STBR_DEBUG_ASSERT(stbr__use_height_upsampling(stbr_info));
STBR_DEBUG_ASSERT(n0 >= in_first_scanline);
STBR_DEBUG_ASSERT(n1 <= in_last_scanline);
@ -658,8 +729,7 @@ static void stbr__resample_vertical_upsample(stbr__info* stbr_info, int n, int i
float* ring_buffer_entry = stbr__get_ring_buffer_scanline(k, ring_buffer, ring_buffer_begin_index, ring_buffer_first_scanline, kernel_texel_width, ring_buffer_length);
float coefficient = vertical_coefficients[coefficient_index];
for (c = 0; c < channels; c++)
encode_buffer[c] += ring_buffer_entry[in_texel_index + c] * coefficient;
output_decode_coefficients_fn(encode_buffer, 0, ring_buffer_entry, in_texel_index, channels, coefficient);
}
for (c = 0; c < channels; c++)
@ -669,7 +739,7 @@ static void stbr__resample_vertical_upsample(stbr__info* stbr_info, int n, int i
static void stbr__resample_vertical_downsample(stbr__info* stbr_info, int n, int in_first_scanline, int in_last_scanline, float in_center_of_out)
{
int x, k, c;
int x, k;
int output_w = stbr_info->output_w;
int output_h = stbr_info->output_h;
stbr__contributors* vertical_contributors = &stbr_info->vertical_contributors;
@ -690,6 +760,8 @@ static void stbr__resample_vertical_downsample(stbr__info* stbr_info, int n, int
int n0 = vertical_contributors->n0;
int n1 = vertical_contributors->n1;
stbr__output_decode_coefficients output_decode_coefficients_fn = stbr__get_output_decode_coefficients_function(channels);
STBR_DEBUG_ASSERT(!stbr__use_height_upsampling(stbr_info));
STBR_DEBUG_ASSERT(n0 >= in_first_scanline);
STBR_DEBUG_ASSERT(n1 <= in_last_scanline);
@ -708,13 +780,7 @@ static void stbr__resample_vertical_downsample(stbr__info* stbr_info, int n, int
float* ring_buffer_entry = stbr__get_ring_buffer_scanline(k, ring_buffer, ring_buffer_begin_index, ring_buffer_first_scanline, kernel_texel_width, ring_buffer_length);
float coefficient = vertical_coefficients[coefficient_index];
for (c = 0; c < channels; c++)
{
int index = in_texel_index + c;
ring_buffer_entry[index] += horizontal_buffer[index] * coefficient;
STBR_DEBUG_ASSERT(ring_buffer_entry[index] <= 1.0); // This would indicate that the sum of kernels for this texel doesn't add to 1.
}
output_decode_coefficients_fn(ring_buffer_entry, in_texel_index, horizontal_buffer, in_texel_index, channels, coefficient);
}
}
}