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Add new opt_mem_priority pass.

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Marcelina Kościelnicka 2021-08-12 03:31:56 +02:00
parent 30927df881
commit 616ace2d92
4 changed files with 319 additions and 2 deletions
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passes/opt/opt_mem_priority.cc Normal file
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/*
* yosys -- Yosys Open SYnthesis Suite
*
* Copyright (C) 2021 Marcelina Kościelnicka <mwk@0x04.net>
*
* Permission to use, copy, modify, and/or distribute this software for any
* purpose with or without fee is hereby granted, provided that the above
* copyright notice and this permission notice appear in all copies.
*
* THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
* WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
* MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
* ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
* WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
* ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
* OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
*
*/
#include "kernel/yosys.h"
#include "kernel/modtools.h"
#include "kernel/qcsat.h"
#include "kernel/mem.h"
USING_YOSYS_NAMESPACE
PRIVATE_NAMESPACE_BEGIN
struct OptMemPriorityPass : public Pass {
OptMemPriorityPass() : Pass("opt_mem_priority", "remove priority relations between write ports that can never collide") { }
void help() override
{
// |---v---|---v---|---v---|---v---|---v---|---v---|---v---|---v---|---v---|---v---|
log("\n");
log(" opt_mem_priority [selection]\n");
log("\n");
log("This pass detects cases where one memory write port has priority over another\n");
log("even though they can never collide with each other — ie. there can never be\n");
log("a situation where a given memory bit is written by both ports at the same\n");
log("time, for example because of always-different addresses, or mutually exclusive\n");
log("enable signals. In such cases, the priority relation is removed.\n");
log("\n");
}
void execute(std::vector<std::string> args, RTLIL::Design *design) override {
log_header(design, "Executing OPT_MEM_PRIORITY pass (removing unnecessary memory write priority relations).\n");
extra_args(args, 1, design);
ModWalker modwalker(design);
int total_count = 0;
for (auto module : design->selected_modules()) {
modwalker.setup(module);
for (auto &mem : Mem::get_selected_memories(module)) {
bool mem_changed = false;
QuickConeSat qcsat(modwalker);
for (int i = 0; i < GetSize(mem.wr_ports); i++) {
auto &wport1 = mem.wr_ports[i];
for (int j = 0; j < GetSize(mem.wr_ports); j++) {
auto &wport2 = mem.wr_ports[j];
if (!wport1.priority_mask[j])
continue;
// No mixed width support — we could do it, but
// that would complicate code and wouldn't help
// anything since we run this pass before
// wide ports are created in normal flow.
if (wport1.wide_log2 != wport2.wide_log2)
continue;
// Two ports with priority, let's go.
pool<std::pair<SigBit, SigBit>> checked;
SigSpec addr1 = wport1.addr;
SigSpec addr2 = wport2.addr;
int abits = std::max(GetSize(addr1), GetSize(addr2));
addr1.extend_u0(abits);
addr2.extend_u0(abits);
int addr_eq = qcsat.ez->vec_eq(qcsat.importSig(addr1), qcsat.importSig(addr2));
bool ok = true;
for (int k = 0; k < GetSize(wport1.data); k++) {
SigBit wen1 = wport1.en[k];
SigBit wen2 = wport2.en[k];
if (checked.count({wen1, wen2}))
continue;
int wen1_sat = qcsat.importSigBit(wen1);
int wen2_sat = qcsat.importSigBit(wen2);
qcsat.prepare();
if (qcsat.ez->solve(wen1_sat, wen2_sat, addr_eq)) {
ok = false;
break;
}
checked.insert({wen1, wen2});
}
if (ok) {
total_count++;
mem_changed = true;
wport1.priority_mask[j] = false;
}
}
}
if (mem_changed)
mem.emit();
}
}
if (total_count)
design->scratchpad_set_bool("opt.did_something", true);
log("Performed a total of %d transformations.\n", total_count);
}
} OptMemPriorityPass;
PRIVATE_NAMESPACE_END