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The shift goes the other way in descending mode.

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This commit is contained in:
Thomas Harte 2021-10-16 11:09:40 -07:00
parent 15ed4a0d09
commit 4917556a99
1 changed files with 25 additions and 2 deletions
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27
Machines/Amiga/Blitter.cpp
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@ -207,18 +207,41 @@ bool Blitter::advance() {
// printf("*** [%d x %d]\n", width_, height_);
// Quick hack: do the entire action atomically.
if(channel_enables_[0]) a_ = 0;
if(channel_enables_[1]) b_ = 0;
if(channel_enables_[2]) c_ = 0;
for(int y = 0; y < height_; y++) {
for(int x = 0; x < width_; x++) {
if(channel_enables_[0]) {
a32_ = (a32_ << 16) | ram_[pointer_[0] & ram_mask_];
a_ = uint16_t(a32_ >> shifts_[0]);
pointer_[0] += direction_;
// The barrel shifter shifts to the right in ascending address mode,
// but to the left othrwise
if(!one_dot_) {
a_ = uint16_t(a32_ >> shifts_[0]);
} else {
// TODO: there must be a neater solution than this.
a_ = uint16_t(
(a32_ << shifts_[0]) |
(a32_ >> (32 - shifts_[0]))
);
}
}
if(channel_enables_[1]) {
b32_ = (b32_ << 16) | ram_[pointer_[1] & ram_mask_];
b_ = uint16_t(b32_ >> shifts_[1]);
pointer_[1] += direction_;
if(!one_dot_) {
b_ = uint16_t(b32_ >> shifts_[1]);
} else {
b_ = uint16_t(
(b32_ << shifts_[1]) |
(b32_ >> (32 - shifts_[1]))
);
}
}
if(channel_enables_[2]) {