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Reduces line drawing to two accesses per slot.

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Still a fiction, but a better one.
This commit is contained in:
Thomas Harte 2022-08-07 19:15:03 -04:00
parent 7f423e39ed
commit 867769f6e7
2 changed files with 66 additions and 61 deletions
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124
Machines/Amiga/Blitter.cpp
View File

@ -292,70 +292,75 @@ bool Blitter<record_bus>::advance_dma() {
// at https://github.com/niklasekstrom/blitter-subpixel-line/blob/master/Drawing%20lines%20using%20the%20Amiga%20blitter.pdf
//
int error = int16_t(pointer_[0] << 1) >> 1; // TODO: what happens if line_sign_ doesn't agree with this?
bool draw_ = true;
while(height_--) {
if(!busy_) {
error_ = int16_t(pointer_[0] << 1) >> 1; // TODO: what happens if line_sign_ doesn't agree with this?
draw_ = true;
busy_ = true;
}
if(draw_) {
// TODO: patterned lines. Unclear what to do with the bit that comes out of b.
// Probably extend it to a full word?
c_data_ = ram_[pointer_[3] & ram_mask_];
if constexpr (record_bus) {
transactions_.emplace_back(Transaction::Type::ReadC, pointer_[3], c_data_);
}
const uint16_t output =
apply_minterm<uint16_t>(a_data_ >> shifts_[0], b_data_, c_data_, minterms_);
ram_[pointer_[3] & ram_mask_] = output;
not_zero_flag_ |= output;
draw_ &= !one_dot_;
if constexpr (record_bus) {
transactions_.emplace_back(Transaction::Type::WriteFromPipeline, pointer_[3], output);
}
if(draw_) {
// TODO: patterned lines. Unclear what to do with the bit that comes out of b.
// Probably extend it to a full word?
c_data_ = ram_[pointer_[3] & ram_mask_];
if constexpr (record_bus) {
transactions_.emplace_back(Transaction::Type::ReadC, pointer_[3], c_data_);
}
constexpr int LEFT = 1 << 0;
constexpr int RIGHT = 1 << 1;
constexpr int UP = 1 << 2;
constexpr int DOWN = 1 << 3;
int step = (line_direction_ & 4) ?
((line_direction_ & 1) ? LEFT : RIGHT) :
((line_direction_ & 1) ? UP : DOWN);
if(error < 0) {
error += modulos_[1];
} else {
step |=
(line_direction_ & 4) ?
((line_direction_ & 2) ? UP : DOWN) :
((line_direction_ & 2) ? LEFT : RIGHT);
error += modulos_[0];
}
if(step & LEFT) {
--shifts_[0];
if(shifts_[0] == -1) {
--pointer_[3];
}
} else if(step & RIGHT) {
++shifts_[0];
if(shifts_[0] == 16) {
++pointer_[3];
}
}
shifts_[0] &= 15;
if(step & UP) {
pointer_[3] -= modulos_[2];
draw_ = true;
} else if(step & DOWN) {
pointer_[3] += modulos_[2];
draw_ = true;
const uint16_t output =
apply_minterm<uint16_t>(a_data_ >> shifts_[0], b_data_, c_data_, minterms_);
ram_[pointer_[3] & ram_mask_] = output;
not_zero_flag_ |= output;
draw_ &= !one_dot_;
if constexpr (record_bus) {
transactions_.emplace_back(Transaction::Type::WriteFromPipeline, pointer_[3], output);
}
}
busy_ = false;
constexpr int LEFT = 1 << 0;
constexpr int RIGHT = 1 << 1;
constexpr int UP = 1 << 2;
constexpr int DOWN = 1 << 3;
int step = (line_direction_ & 4) ?
((line_direction_ & 1) ? LEFT : RIGHT) :
((line_direction_ & 1) ? UP : DOWN);
if(error_ < 0) {
error_ += modulos_[1];
} else {
step |=
(line_direction_ & 4) ?
((line_direction_ & 2) ? UP : DOWN) :
((line_direction_ & 2) ? LEFT : RIGHT);
error_ += modulos_[0];
}
if(step & LEFT) {
--shifts_[0];
if(shifts_[0] == -1) {
--pointer_[3];
}
} else if(step & RIGHT) {
++shifts_[0];
if(shifts_[0] == 16) {
++pointer_[3];
}
}
shifts_[0] &= 15;
if(step & UP) {
pointer_[3] -= modulos_[2];
draw_ = true;
} else if(step & DOWN) {
pointer_[3] += modulos_[2];
draw_ = true;
}
--height_;
if(!height_) {
busy_ = false;
posit_interrupt(InterruptFlag::Blitter);
}
} else {
// Copy mode.
if(!busy_) {
@ -518,9 +523,6 @@ bool Blitter<record_bus>::advance_dma() {
}
}
posit_interrupt(InterruptFlag::Blitter);
height_ = 0;
return true;
}

3
Machines/Amiga/Blitter.hpp
View File

@ -261,6 +261,9 @@ template <bool record_bus = false> class Blitter: public DMADevice<4, 4> {
bool busy_ = false;
int loop_index_ = -1;
int error_ = 0;
bool draw_ = false;
void add_modulos();
std::vector<Transaction> transactions_;
};