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memory_share: Add read port merging.

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This is mostly meant for wide port recognition, but may also happen to
merge some ports with compatible initial/reset values (eg. 0 vs x).
This commit is contained in:
Marcelina Kościelnicka 2020-10-26 00:44:37 +01:00
parent 2d10caabbc
commit 82f5829aba
1 changed files with 140 additions and 0 deletions
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140
passes/memory/memory_share.cc
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@ -36,6 +36,145 @@ struct MemoryShareWorker
bool flag_widen;
// --------------------------------------------------
// Consolidate read ports that read the same address
// (or close enough to be merged to wide ports)
// --------------------------------------------------
// A simple function to detect ports that couldn't possibly collide
// because of opposite const address bits (simplistic, but enough
// to fix problems with inferring wide ports).
bool rdwr_can_collide(Mem &mem, int ridx, int widx) {
auto &rport = mem.rd_ports[ridx];
auto &wport = mem.wr_ports[widx];
for (int i = std::max(rport.wide_log2, wport.wide_log2); i < GetSize(rport.addr) && i < GetSize(wport.addr); i++) {
if (rport.addr[i] == State::S1 && wport.addr[i] == State::S0)
return false;
if (rport.addr[i] == State::S0 && wport.addr[i] == State::S1)
return false;
}
return true;
}
bool merge_rst_value(Mem &mem, Const &res, int wide_log2, const Const &src1, int sub1, const Const &src2, int sub2) {
res = Const(State::Sx, mem.width << wide_log2);
for (int i = 0; i < GetSize(src1); i++)
res[i + sub1 * mem.width] = src1[i];
for (int i = 0; i < GetSize(src2); i++) {
if (src2[i] == State::Sx)
continue;
auto &dst = res[i + sub2 * mem.width];
if (dst == src2[i])
continue;
if (dst != State::Sx)
return false;
dst = src2[i];
}
return true;
}
bool consolidate_rd_by_addr(Mem &mem)
{
if (GetSize(mem.rd_ports) <= 1)
return false;
log("Consolidating read ports of memory %s.%s by address:\n", log_id(module), log_id(mem.memid));
bool changed = false;
for (int i = 0; i < GetSize(mem.rd_ports); i++)
{
auto &port1 = mem.rd_ports[i];
if (port1.removed)
continue;
for (int j = i + 1; j < GetSize(mem.rd_ports); j++)
{
auto &port2 = mem.rd_ports[j];
if (port2.removed)
continue;
if (port1.clk_enable != port2.clk_enable)
continue;
if (port1.clk_enable) {
if (port1.clk != port2.clk)
continue;
if (port1.clk_polarity != port2.clk_polarity)
continue;
}
if (port1.en != port2.en)
continue;
if (port1.arst != port2.arst)
continue;
if (port1.srst != port2.srst)
continue;
if (port1.ce_over_srst != port2.ce_over_srst)
continue;
if (port1.transparent != port2.transparent)
continue;
// If the width of the ports doesn't match, they can still be
// merged by widening the narrow one. Check if the conditions
// hold for that.
int wide_log2 = std::max(port1.wide_log2, port2.wide_log2);
if (GetSize(port1.addr) <= wide_log2)
continue;
if (GetSize(port2.addr) <= wide_log2)
continue;
if (!port1.addr.extract(0, wide_log2).is_fully_const())
continue;
if (!port2.addr.extract(0, wide_log2).is_fully_const())
continue;
if (sigmap_xmux(port1.addr.extract_end(wide_log2)) != sigmap_xmux(port2.addr.extract_end(wide_log2))) {
// Incompatible addresses after widening. Last chance — widen both
// ports by one more bit to merge them.
if (!flag_widen)
continue;
wide_log2++;
if (sigmap_xmux(port1.addr.extract_end(wide_log2)) != sigmap_xmux(port2.addr.extract_end(wide_log2)))
continue;
if (!port1.addr.extract(0, wide_log2).is_fully_const())
continue;
if (!port2.addr.extract(0, wide_log2).is_fully_const())
continue;
}
// Combine init/reset values.
SigSpec sub1_c = port1.addr.extract(0, wide_log2);
log_assert(sub1_c.is_fully_const());
int sub1 = sub1_c.as_int();
SigSpec sub2_c = port2.addr.extract(0, wide_log2);
log_assert(sub2_c.is_fully_const());
int sub2 = sub2_c.as_int();
Const init_value, arst_value, srst_value;
if (!merge_rst_value(mem, init_value, wide_log2, port1.init_value, sub1, port2.init_value, sub2))
continue;
if (!merge_rst_value(mem, arst_value, wide_log2, port1.arst_value, sub1, port2.arst_value, sub2))
continue;
if (!merge_rst_value(mem, srst_value, wide_log2, port1.srst_value, sub1, port2.srst_value, sub2))
continue;
{
log(" Merging ports %d, %d (address %s).\n", i, j, log_signal(port1.addr));
mem.widen_prep(wide_log2);
SigSpec new_data = module->addWire(NEW_ID, mem.width << wide_log2);
module->connect(port1.data, new_data.extract(sub1 * mem.width, mem.width << port1.wide_log2));
module->connect(port2.data, new_data.extract(sub2 * mem.width, mem.width << port2.wide_log2));
port1.addr = sigmap_xmux(port1.addr);
for (int k = 0; k < wide_log2; k++)
port1.addr[k] = State::S0;
port1.init_value = init_value;
port1.arst_value = arst_value;
port1.srst_value = srst_value;
port1.wide_log2 = wide_log2;
port1.data = new_data;
port2.removed = true;
changed = true;
}
}
}
if (changed)
mem.emit();
return changed;
}
// ------------------------------------------------------
// Consolidate write ports that write to the same address
// (or close enough to be merged to wide ports)
@ -370,6 +509,7 @@ struct MemoryShareWorker
}
for (auto &mem : memories) {
while (consolidate_rd_by_addr(mem));
while (consolidate_wr_by_addr(mem));
}