diff options
Diffstat (limited to 'passes/opt/opt_mem_priority.cc')
| -rw-r--r-- | passes/opt/opt_mem_priority.cc | 109 |
1 files changed, 109 insertions, 0 deletions
diff --git a/passes/opt/opt_mem_priority.cc b/passes/opt/opt_mem_priority.cc new file mode 100644 index 000000000..49ece570b --- /dev/null +++ b/passes/opt/opt_mem_priority.cc @@ -0,0 +1,109 @@ +/* + * 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 + |