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Merge pull request #727 from whitequark/opt_lut

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opt_lut: leave intact LUTs with cascade feeding module outputs
This commit is contained in:
David Shah 2018-12-07 17:17:26 +00:00 • committed by GitHub
commit 435776120a
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3 changed files with 50 additions and 5 deletions
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35
passes/opt/opt_lut.cc
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@ -93,7 +93,7 @@ struct OptLutWorker
} }
} }
OptLutWorker(dict<IdString, dict<int, IdString>> &dlogic, RTLIL::Module *module) : OptLutWorker(dict<IdString, dict<int, IdString>> &dlogic, RTLIL::Module *module, int limit) :
dlogic(dlogic), module(module), index(module), sigmap(module) dlogic(dlogic), module(module), index(module), sigmap(module)
{ {
log("Discovering LUTs.\n"); log("Discovering LUTs.\n");
@ -192,6 +192,12 @@ struct OptLutWorker
pool<RTLIL::Cell*> worklist = luts; pool<RTLIL::Cell*> worklist = luts;
while (worklist.size()) while (worklist.size())
{ {
if (limit == 0)
{
log("Limit reached.\n");
break;
}
auto lutA = worklist.pop(); auto lutA = worklist.pop();
SigSpec lutA_input = sigmap(lutA->getPort("\\A")); SigSpec lutA_input = sigmap(lutA->getPort("\\A"));
SigSpec lutA_output = sigmap(lutA->getPort("\\Y")[0]); SigSpec lutA_output = sigmap(lutA->getPort("\\Y")[0]);
@ -219,6 +225,12 @@ struct OptLutWorker
log("Found %s.%s (cell A) feeding %s.%s (cell B).\n", log_id(module), log_id(lutA), log_id(module), log_id(lutB)); log("Found %s.%s (cell A) feeding %s.%s (cell B).\n", log_id(module), log_id(lutA), log_id(module), log_id(lutB));
if (index.query_is_output(lutA->getPort("\\Y")))
{
log(" Not combining LUTs (cascade connection feeds module output).\n");
continue;
}
pool<SigBit> lutA_inputs; pool<SigBit> lutA_inputs;
pool<SigBit> lutB_inputs; pool<SigBit> lutB_inputs;
for (auto &bit : lutA_input) for (auto &bit : lutA_input)
@ -382,8 +394,9 @@ struct OptLutWorker
lutM_new_table[eval] = (RTLIL::State) evaluate_lut(lutB, eval_inputs); lutM_new_table[eval] = (RTLIL::State) evaluate_lut(lutB, eval_inputs);
} }
log(" Old truth table: %s.\n", lutM->getParam("\\LUT").as_string().c_str()); log(" Cell A truth table: %s.\n", lutA->getParam("\\LUT").as_string().c_str());
log(" New truth table: %s.\n", lutM_new_table.as_string().c_str()); log(" Cell B truth table: %s.\n", lutB->getParam("\\LUT").as_string().c_str());
log(" Merged truth table: %s.\n", lutM_new_table.as_string().c_str());
lutM->setParam("\\LUT", lutM_new_table); lutM->setParam("\\LUT", lutM_new_table);
lutM->setPort("\\A", lutM_new_inputs); lutM->setPort("\\A", lutM_new_inputs);
@ -398,6 +411,8 @@ struct OptLutWorker
worklist.erase(lutR); worklist.erase(lutR);
combined_count++; combined_count++;
if (limit > 0)
limit--;
} }
} }
} }
@ -431,17 +446,22 @@ struct OptLutPass : public Pass {
log(" the case where both LUT and dedicated logic input are connected to\n"); log(" the case where both LUT and dedicated logic input are connected to\n");
log(" the same constant.\n"); log(" the same constant.\n");
log("\n"); log("\n");
log(" -limit N\n");
log(" only perform the first N combines, then stop. useful for debugging.\n");
log("\n");
} }
void execute(std::vector<std::string> args, RTLIL::Design *design) YS_OVERRIDE void execute(std::vector<std::string> args, RTLIL::Design *design) YS_OVERRIDE
{ {
log_header(design, "Executing OPT_LUT pass (optimize LUTs).\n"); log_header(design, "Executing OPT_LUT pass (optimize LUTs).\n");
dict<IdString, dict<int, IdString>> dlogic; dict<IdString, dict<int, IdString>> dlogic;
int limit = -1;
size_t argidx; size_t argidx;
for (argidx = 1; argidx < args.size(); argidx++) for (argidx = 1; argidx < args.size(); argidx++)
{ {
if (args[argidx] == "-dlogic" && argidx+1 < args.size()) { if (args[argidx] == "-dlogic" && argidx+1 < args.size())
{
std::vector<std::string> tokens; std::vector<std::string> tokens;
split(tokens, args[++argidx], ':'); split(tokens, args[++argidx], ':');
if (tokens.size() < 2) if (tokens.size() < 2)
@ -458,6 +478,11 @@ struct OptLutPass : public Pass {
} }
continue; continue;
} }
if (args[argidx] == "-limit" && argidx + 1 < args.size())
{
limit = atoi(args[++argidx].c_str());
continue;
}
break; break;
} }
extra_args(args, argidx, design); extra_args(args, argidx, design);
@ -465,7 +490,7 @@ struct OptLutPass : public Pass {
int total_count = 0; int total_count = 0;
for (auto module : design->selected_modules()) for (auto module : design->selected_modules())
{ {
OptLutWorker worker(dlogic, module); OptLutWorker worker(dlogic, module, limit - total_count);
total_count += worker.combined_count; total_count += worker.combined_count;
} }
if (total_count) if (total_count)

18
tests/opt/opt_lut_port.il Normal file
View file

@ -0,0 +1,18 @@
module $1
wire width 4 input 2 \_0_
wire output 4 \_1_
wire input 3 \_2_
wire output 1 \o
cell $lut \_3_
parameter \LUT 16'0011000000000011
parameter \WIDTH 4
connect \A { \_0_ [3] \o 2'00 }
connect \Y \_1_
end
cell $lut \_4_
parameter \LUT 4'0001
parameter \WIDTH 4
connect \A { 3'000 \_2_ }
connect \Y \o
end
end

2
tests/opt/opt_lut_port.ys Normal file
View file

@ -0,0 +1,2 @@
read_ilang opt_lut_port.il
select -assert-count 2 t:$lut