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Optimises the inner TMS loops slightly.

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This commit is contained in:
Thomas Harte 2018-02-21 21:29:17 -05:00
parent a4dc9c0403
commit cabad6fc05
1 changed files with 31 additions and 12 deletions
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43
Components/9918/9918.cpp
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@ -53,6 +53,25 @@ const uint8_t StatusFifthSprite = 0x40;
const int StatusSpriteCollisionShift = 5;
const uint8_t StatusSpriteCollision = 0x20;
struct ReverseTable {
std::uint8_t map[256];
ReverseTable() {
for(int c = 0; c < 256; ++c) {
map[c] = static_cast<uint8_t>(
((c & 0x80) >> 7) |
((c & 0x40) >> 5) |
((c & 0x20) >> 3) |
((c & 0x10) >> 1) |
((c & 0x08) << 1) |
((c & 0x04) << 3) |
((c & 0x02) << 5) |
((c & 0x01) << 7)
);
}
}
} reverse_table;
}
TMS9918Base::TMS9918Base() :
@ -380,21 +399,21 @@ void TMS9918::run_for(const HalfCycles cycles) {
const int shift = (output_column_ - first_pixel_column_) % 6;
int byte_column = (output_column_ - first_pixel_column_) / 6;
int pattern = pattern_buffer_[byte_column] << shift;
int pattern = reverse_table.map[pattern_buffer_[byte_column]] >> shift;
int pixels_left = pixels_end - output_column_;
int length = std::min(pixels_left, 6 - shift);
while(true) {
pixels_left -= length;
while(length--) {
*pixel_target_ = colours[(pattern >> 7)&0x01];
pixel_target_++;
pattern <<= 1;
for(int c = 0; c < length; ++c) {
pixel_target_[c] = colours[pattern&0x01];
pattern >>= 1;
}
pixel_target_ += length;
if(!pixels_left) break;
length = std::min(6, pixels_left);
byte_column++;
pattern = pattern_buffer_[byte_column];
pattern = reverse_table.map[pattern_buffer_[byte_column]];
}
output_column_ = pixels_end;
} break;
@ -422,7 +441,7 @@ void TMS9918::run_for(const HalfCycles cycles) {
const int pixels_left = pixels_end - output_column_;
int length = std::min(pixels_left, 8 - shift);
int pattern = pattern_buffer_[byte_column] << shift;
int pattern = reverse_table.map[pattern_buffer_[byte_column]] >> shift;
uint8_t colour = colour_buffer_[byte_column];
uint32_t colours[2] = {
palette[(colour & 15) ? (colour & 15) : background_colour_],
@ -432,17 +451,17 @@ void TMS9918::run_for(const HalfCycles cycles) {
int background_pixels_left = pixels_left;
while(true) {
background_pixels_left -= length;
while(length--) {
*pixel_target_ = colours[(pattern >> 7)&0x01];
pixel_target_++;
pattern <<= 1;
for(int c = 0; c < length; ++c) {
pixel_target_[c] = colours[pattern&0x01];
pattern >>= 1;
}
pixel_target_ += length;
if(!background_pixels_left) break;
length = std::min(8, background_pixels_left);
byte_column++;
pattern = pattern_buffer_[byte_column];
pattern = reverse_table.map[pattern_buffer_[byte_column]];
colour = colour_buffer_[byte_column];
colours[0] = palette[(colour & 15) ? (colour & 15) : background_colour_];
colours[1] = palette[(colour >> 4) ? (colour >> 4) : background_colour_];