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opt_dff: Change AD to const if it's identical or complementary to ALOAD

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devsaurus 2026-01-03 12:03:46 +01:00
parent 8101c87fab
commit 97d3f07e78
2 changed files with 173 additions and 0 deletions
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64
passes/opt/opt_dff.cc
View file

@ -907,6 +907,68 @@ struct OptDffWorker
ff.emit();
return did_something;
}
bool run_related_load_data() {
ModWalker modwalker(module->design, module);
QuickConeSat qcsat(modwalker);
// Defer mutating cells by emiting new flip flops so that
// cell references in modwalker are not invalidated
std::vector<FfData> ffs_to_emit;
bool did_something = false;
for (auto cell : module->selected_cells()) {
if (!cell->is_builtin_ff())
continue;
FfData ff(&initvals, cell);
if (ff.has_aload) {
if (!ff.sig_aload[0].wire)
continue;
bool changed_ff = false;
for (int i = 0; i < ff.width; i++) {
if (!ff.sig_ad[i].wire) {
// Nothing to do
continue;
}
// Change AD to const if it's identical or complementary to ALOAD.
if (ff.sig_aload == ff.sig_ad[i]) {
log("Changing same-signal async load to constant at position %d on %s (%s) from module %s.\n",
i, log_id(cell), log_id(cell->type), log_id(module));
ff.sig_ad[i] = ff.pol_aload ? State::S1 : State::S0;
changed_ff = true;
} else {
if (!opt.sat)
continue;
int aload_pol_sat_pi = qcsat.importSigBit(ff.pol_aload ? State::S1 : State::S0);
int aload_not_pol_sat_pi = qcsat.importSigBit(ff.pol_aload ? State::S0 : State::S1);
int aload_sat_pi = qcsat.importSigBit(ff.sig_aload);
int ad_sat_pi = qcsat.importSigBit(ff.sig_ad[i]);
qcsat.prepare();
if (!qcsat.ez->solve(qcsat.ez->IFF(aload_sat_pi, aload_pol_sat_pi), qcsat.ez->NOT(qcsat.ez->IFF(ad_sat_pi, aload_not_pol_sat_pi)))) {
log("Changing comp-signal async load to constant at position %d on %s (%s) from module %s.\n",
i, log_id(cell), log_id(cell->type), log_id(module));
ff.sig_ad[i] = ff.pol_aload ? State::S0 : State::S1;
changed_ff = true;
}
}
}
if (changed_ff) {
ffs_to_emit.emplace_back(ff);
did_something = true;
}
}
}
for (auto& ff : ffs_to_emit)
ff.emit();
return did_something;
}
};
struct OptDffPass : public Pass {
@ -986,6 +1048,8 @@ struct OptDffPass : public Pass {
OptDffWorker worker(opt, mod);
if (worker.run())
did_something = true;
if (worker.run_related_load_data())
did_something = true;
if (worker.run_constbits())
did_something = true;
}

109
tests/opt/opt_dff_aload.ys Normal file
View file

@ -0,0 +1,109 @@
### ALOAD and AD same/complementary-signal optimization
read_verilog -icells <<EOT
module top(...);
input CLK;
input [1:0] D;
output [15:0] Q;
input ALOAD;
input ARST;
input EN;
wire nALOAD_not;
$not #(.A_SIGNED(0), .A_WIDTH(1), .Y_WIDTH(1)) not0 (.Y(nALOAD_not), .A(ALOAD));
wire nALOAD_mux;
$mux #(.WIDTH(1)) mux0 (.Y(nALOAD_mux), .A(1'b1), .B(1'b0), .S(ALOAD));
$aldff #(.CLK_POLARITY(1'b1), .ALOAD_POLARITY(1'b1), .WIDTH(2)) ff0 (.CLK(CLK), .D(D), .Q(Q[1:0]), .ALOAD(ALOAD), .AD({ALOAD, ALOAD}));
$aldff #(.CLK_POLARITY(1'b1), .ALOAD_POLARITY(1'b0), .WIDTH(2)) ff1 (.CLK(CLK), .D(D), .Q(Q[3:2]), .ALOAD(ALOAD), .AD({ALOAD, nALOAD_not}));
$aldff #(.CLK_POLARITY(1'b1), .ALOAD_POLARITY(1'b1), .WIDTH(2)) ff2 (.CLK(CLK), .D(D), .Q(Q[5:4]), .ALOAD(ALOAD), .AD({nALOAD_mux, ALOAD}));
$aldff #(.CLK_POLARITY(1'b1), .ALOAD_POLARITY(1'b0), .WIDTH(2)) ff3 (.CLK(CLK), .D(D), .Q(Q[7:6]), .ALOAD(ALOAD), .AD({nALOAD_not, nALOAD_mux}));
$aldffe #(.CLK_POLARITY(1'b1), .ALOAD_POLARITY(1'b1), .EN_POLARITY(1'b1), .WIDTH(2)) ff4 (.CLK(CLK), .D(D), .EN(EN), .Q(Q[9:8]), .ALOAD(nALOAD_not), .AD({ALOAD, ALOAD}));
$aldffe #(.CLK_POLARITY(1'b1), .ALOAD_POLARITY(1'b0), .EN_POLARITY(1'b1), .WIDTH(2)) ff5 (.CLK(CLK), .D(D), .EN(EN), .Q(Q[11:10]), .ALOAD(nALOAD_mux), .AD({ALOAD, nALOAD_mux}));
$aldffe #(.CLK_POLARITY(1'b1), .ALOAD_POLARITY(1'b1), .EN_POLARITY(1'b1), .WIDTH(2)) ff6 (.CLK(CLK), .D(D), .EN(EN), .Q(Q[13:12]), .ALOAD(nALOAD_not), .AD({nALOAD_not, ALOAD}));
$aldffe #(.CLK_POLARITY(1'b1), .ALOAD_POLARITY(1'b0), .EN_POLARITY(1'b1), .WIDTH(2)) ff7 (.CLK(CLK), .D(D), .EN(EN), .Q(Q[15:14]), .ALOAD(nALOAD_mux), .AD({nALOAD_mux, nALOAD_not}));
endmodule
EOT
design -save orig
# Change same/complementary-signal AD to constant async load
# Then change const-value async load to async reset adff
equiv_opt -undef -assert -multiclock opt -sat
design -load postopt
# Check that all aldff* were transformed
select -assert-none t:$aldff*
select -assert-count 8 t:$adff*
design -reset
### EN and D same/complementary-signal optimization
read_verilog -icells <<EOT
module top(...);
input CLK;
output [43:0] Q;
input ARST;
input SET;
input CLR;
input EN;
wire nEN_not;
$not #(.A_SIGNED(0), .A_WIDTH(1), .Y_WIDTH(1)) not0 (.Y(nEN_not), .A(EN));
wire nEN_mux;
$mux #(.WIDTH(1)) mux0 (.Y(nEN_mux), .A(1'b1), .B(1'b0), .S(EN));
$dlatch #(.EN_POLARITY(1'b1), .WIDTH(2)) lch0 (.EN(EN), .D({EN, nEN_not}), .Q(Q[1:0]));
$dlatch #(.EN_POLARITY(1'b1), .WIDTH(2)) lch1 (.EN(EN), .D({nEN_mux, EN}), .Q(Q[3:2]));
$dlatch #(.EN_POLARITY(1'b1), .WIDTH(2)) lch2 (.EN(nEN_not), .D({EN, EN}), .Q(Q[5:4]));
$dlatch #(.EN_POLARITY(1'b0), .WIDTH(2)) lch3 (.EN(nEN_not), .D({EN, nEN_mux}), .Q(Q[7:6]));
$dlatch #(.EN_POLARITY(1'b0), .WIDTH(2)) lch4 (.EN(nEN_mux), .D({nEN_not, EN}), .Q(Q[9:8]));
$dlatch #(.EN_POLARITY(1'b0), .WIDTH(2)) lch5 (.EN(nEN_mux), .D({nEN_mux, nEN_not}), .Q(Q[11:10]));
$adlatch #(.EN_POLARITY(1'b1), .ARST_POLARITY(1'b1), .ARST_VALUE(2'b10), .WIDTH(2)) lch6 (.EN(EN), .ARST(ARST), .D({EN, nEN_not}), .Q(Q[13:12]));
$adlatch #(.EN_POLARITY(1'b1), .ARST_POLARITY(1'b1), .ARST_VALUE(2'b01), .WIDTH(2)) lch7 (.EN(EN), .ARST(ARST), .D({nEN_mux, EN}), .Q(Q[15:14]));
$adlatch #(.EN_POLARITY(1'b1), .ARST_POLARITY(1'b1), .ARST_VALUE(2'b00), .WIDTH(2)) lch8 (.EN(nEN_not), .ARST(ARST), .D({EN, EN}), .Q(Q[17:16]));
$adlatch #(.EN_POLARITY(1'b0), .ARST_POLARITY(1'b1), .ARST_VALUE(2'b10), .WIDTH(2)) lch9 (.EN(nEN_not), .ARST(ARST), .D({EN, nEN_mux}), .Q(Q[19:18]));
$adlatch #(.EN_POLARITY(1'b0), .ARST_POLARITY(1'b1), .ARST_VALUE(2'b01), .WIDTH(2)) lch10 (.EN(nEN_mux), .ARST(ARST), .D({nEN_not, EN}), .Q(Q[21:20]));
$adlatch #(.EN_POLARITY(1'b0), .ARST_POLARITY(1'b1), .ARST_VALUE(2'b00), .WIDTH(2)) lch11 (.EN(nEN_mux), .ARST(ARST), .D({nEN_mux, nEN_not}), .Q(Q[23:22]));
$adlatch #(.EN_POLARITY(1'b1), .ARST_POLARITY(1'b1), .ARST_VALUE(2'b01), .WIDTH(2)) lch12 (.EN(EN), .ARST(ARST), .D({nEN_mux, EN}), .Q(Q[25:24]));
$dlatchsr #(.EN_POLARITY(1'b1), .SET_POLARITY(1'b1), .CLR_POLARITY(1'b1), .WIDTH(2)) lch13 (.EN(EN), .SET({SET, 1'b0}), .CLR({1'b0, CLR}), .D({EN, nEN_not}), .Q(Q[27:26]));
$dlatchsr #(.EN_POLARITY(1'b1), .SET_POLARITY(1'b1), .CLR_POLARITY(1'b1), .WIDTH(2)) lch14 (.EN(EN), .SET({1'b0, SET}), .CLR({CLR, 1'b0}), .D({nEN_mux, EN}), .Q(Q[29:28]));
$dlatchsr #(.EN_POLARITY(1'b1), .SET_POLARITY(1'b1), .CLR_POLARITY(1'b1), .WIDTH(2)) lch15 (.EN(nEN_not), .SET({1'b0, 1'b0}), .CLR({CLR, CLR}), .D({EN, EN}), .Q(Q[31:30]));
$dlatchsr #(.EN_POLARITY(1'b0), .SET_POLARITY(1'b1), .CLR_POLARITY(1'b1), .WIDTH(2)) lch16 (.EN(nEN_not), .SET({SET, 1'b0}), .CLR({1'b0, CLR}), .D({EN, nEN_mux}), .Q(Q[33:32]));
$dlatchsr #(.EN_POLARITY(1'b0), .SET_POLARITY(1'b1), .CLR_POLARITY(1'b1), .WIDTH(2)) lch17 (.EN(nEN_mux), .SET({1'b0, SET}), .CLR({CLR, 1'b0}), .D({nEN_not, EN}), .Q(Q[35:34]));
$dlatchsr #(.EN_POLARITY(1'b0), .SET_POLARITY(1'b1), .CLR_POLARITY(1'b1), .WIDTH(2)) lch18 (.EN(nEN_mux), .SET({1'b0, 1'b0}), .CLR({CLR, CLR}), .D({nEN_mux, nEN_not}), .Q(Q[37:36]));
$dlatchsr #(.EN_POLARITY(1'b1), .SET_POLARITY(1'b1), .CLR_POLARITY(1'b1), .WIDTH(2)) lch19 (.EN(EN), .SET({1'b0, SET}), .CLR({CLR, 1'b0}), .D({nEN_mux, EN}), .Q(Q[39:38]));
// These 2 latches are supposed to remain
$adlatch #(.EN_POLARITY(1'b0), .ARST_POLARITY(1'b1), .ARST_VALUE(2'b11), .WIDTH(2)) lch20 (.EN(nEN_mux), .ARST(ARST), .D({nEN_mux, nEN_not}), .Q(Q[41:40]));
$adlatch #(.EN_POLARITY(1'b1), .ARST_POLARITY(1'b1), .ARST_VALUE(2'b10), .WIDTH(2)) lch21 (.EN(EN), .ARST(ARST), .D({nEN_mux, EN}), .Q(Q[43:42]));
endmodule
EOT
design -save orig
# Change same/complementary-signal AD to constant async load
# Then set constant bits
equiv_opt -undef -assert -multiclock opt -sat
design -load postopt
# Check that all intended dlatch, adlatch and dlatchsr were transformed
select -assert-none t:$dlatch*
select -assert-count 2 t:$adlatch*
select -assert-none t:$dlatchsr*
design -reset