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ice40: Add option to only use CE if it'd be use by more than X FFs 

Signed-off-by: Sylvain Munaut <tnt@246tNt.com>
This commit is contained in:
Sylvain Munaut 2018-11-15 02:49:35 +01:00
parent 8d3ab626ea
commit 3e5ab50a73
1 changed files with 14 additions and 0 deletions
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14
techlibs/ice40/synth_ice40.cc
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@ -69,6 +69,10 @@ struct SynthIce40Pass : public ScriptPass
log(" -nodffe\n"); log(" -nodffe\n");
log(" do not use SB_DFFE* cells in output netlist\n"); log(" do not use SB_DFFE* cells in output netlist\n");
log("\n"); log("\n");
log(" -dffe_min_ce_use <min_ce_use>\n");
log(" do not use SB_DFFE* cells if the resulting CE line would go to less\n");
log(" than min_ce_use SB_DFFE*in output netlist\n");
log("\n");
log(" -nobram\n"); log(" -nobram\n");
log(" do not use SB_RAM40_4K* cells in output netlist\n"); log(" do not use SB_RAM40_4K* cells in output netlist\n");
log("\n"); log("\n");
@ -87,6 +91,7 @@ struct SynthIce40Pass : public ScriptPass
string top_opt, blif_file, edif_file, json_file; string top_opt, blif_file, edif_file, json_file;
bool nocarry, nodffe, nobram, flatten, retime, abc2, vpr; bool nocarry, nodffe, nobram, flatten, retime, abc2, vpr;
int min_ce_use;
void clear_flags() YS_OVERRIDE void clear_flags() YS_OVERRIDE
{ {
@ -96,6 +101,7 @@ struct SynthIce40Pass : public ScriptPass
json_file = ""; json_file = "";
nocarry = false; nocarry = false;
nodffe = false; nodffe = false;
min_ce_use = -1;
nobram = false; nobram = false;
flatten = true; flatten = true;
retime = false; retime = false;
@ -155,6 +161,10 @@ struct SynthIce40Pass : public ScriptPass
nodffe = true; nodffe = true;
continue; continue;
} }
if (args[argidx] == "-dffe_min_ce_use" && argidx+1 < args.size()) {
min_ce_use = std::stoi(args[++argidx]);
continue;
}
if (args[argidx] == "-nobram") { if (args[argidx] == "-nobram") {
nobram = true; nobram = true;
continue; continue;
@ -228,6 +238,10 @@ struct SynthIce40Pass : public ScriptPass
run("dffsr2dff"); run("dffsr2dff");
if (!nodffe) if (!nodffe)
run("dff2dffe -direct-match $_DFF_*"); run("dff2dffe -direct-match $_DFF_*");
if (min_ce_use >= 0) {
run("opt_merge");
run(stringf("dff2dffe -unmap-mince %d", min_ce_use));
}
run("techmap -D NO_LUT -map +/ice40/cells_map.v"); run("techmap -D NO_LUT -map +/ice40/cells_map.v");
run("opt_expr -mux_undef"); run("opt_expr -mux_undef");
run("simplemap"); run("simplemap");