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Merge FFs where possible

This commit is contained in:
Miodrag Milanovic 2025-07-10 14:15:55 +02:00
parent f786686d50
commit 3244b09e2c
2 changed files with 78 additions and 33 deletions
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2
himbaechel/uarch/gatemate/pack.h
View File

@ -97,6 +97,8 @@ struct GateMatePacker
uint8_t ram_ctrl_signal(CellInfo *cell, IdString port, bool alt);
uint8_t ram_clk_signal(CellInfo *cell, IdString port);
bool is_gpio_valid_dff(CellInfo *dff);
bool are_ffs_compatible(CellInfo *dff, CellInfo *other);
// Cell creating
CellInfo *create_cell_ptr(IdString type, IdString name);
void flush_cells(bool unbind = false);

109
himbaechel/uarch/gatemate/pack_cpe.cc
View File

@ -29,6 +29,21 @@ NEXTPNR_NAMESPACE_BEGIN
// Return true if a cell is a flipflop
inline bool is_dff(const BaseCtx *ctx, const CellInfo *cell) { return cell->type.in(id_CC_DFF, id_CC_DLT); }
bool GateMatePacker::are_ffs_compatible(CellInfo *dff, CellInfo *other)
{
if (!other)
return true;
if (dff->getPort(id_CLK) != other->getPort(id_CLK))
return false;
if (dff->getPort(id_EN) != other->getPort(id_EN))
return false;
if (dff->getPort(id_SR) != other->getPort(id_SR))
return false;
if (uarch->get_dff_config(dff) != uarch->get_dff_config(other))
return false;
return true;
}
void GateMatePacker::dff_to_cpe(CellInfo *dff)
{
bool invert;
@ -158,10 +173,24 @@ void GateMatePacker::pack_cpe()
int l2t4_created = 0;
int mx4_created = 0;
int ff_created = 0;
auto merge_dff = [&](CellInfo &ci, CellInfo *dff) {
dff->cluster = ci.name;
dff->constr_abs_z = false;
dff->constr_z = +2;
ci.cluster = ci.name;
ci.constr_children.push_back(dff);
dff->renamePort(id_D, id_DIN);
dff->renamePort(id_Q, id_DOUT);
dff->type = (dff->type == id_CC_DLT) ? id_CPE_LATCH : id_CPE_FF;
ff_created++;
};
for (auto &cell : ctx->cells) {
CellInfo &ci = *cell.second;
if (!ci.type.in(id_CC_L2T4, id_CC_L2T5, id_CC_LUT2, id_CC_LUT1, id_CC_MX2))
continue;
bool is_l2t5 = false;
if (ci.type == id_CC_L2T5) {
l2t5_list.push_back(&ci);
ci.renamePort(id_I0, id_IN1);
@ -178,6 +207,7 @@ void GateMatePacker::pack_cpe()
ci.constr_z = CPE_LT_L_Z;
ci.type = id_CPE_L2T4;
l2t4_created++;
is_l2t5 = true;
} else if (ci.type == id_CC_MX2) {
ci.renamePort(id_D1, id_IN1);
NetInfo *sel = ci.getPort(id_S0);
@ -212,17 +242,48 @@ void GateMatePacker::pack_cpe()
}
NetInfo *o = ci.getPort(id_OUT);
if (o) {
CellInfo *dff = net_only_drives(ctx, o, is_dff, id_D, true);
if (dff) {
dff->cluster = ci.name;
dff->constr_abs_z = false;
dff->constr_z = +2;
ci.cluster = ci.name;
ci.constr_children.push_back(dff);
dff->renamePort(id_D, id_DIN);
dff->renamePort(id_Q, id_DOUT);
dff->type = (dff->type == id_CC_DLT) ? id_CPE_LATCH : id_CPE_FF;
ff_created++;
if (o->users.entries() == 1) {
// When only it is driving FF
CellInfo *dff = net_only_drives(ctx, o, is_dff, id_D, true);
if (dff)
merge_dff(ci, dff);
} else if (!is_l2t5) {
CellInfo *dff = net_only_drives(ctx, o, is_dff, id_D, false);
// When driving FF + other logic
if (dff) {
// Make sure main logic is in upper half
ci.constr_abs_z = true;
ci.constr_z = CPE_LT_U_Z;
merge_dff(ci, dff);
// Lower half propagate output from upper one
CellInfo *lower = create_cell_ptr(id_CPE_L2T4, ctx->idf("%s$lower", ci.name.c_str(ctx)));
ci.constr_children.push_back(lower);
lower->cluster = ci.name;
lower->constr_abs_z = true;
lower->constr_z = CPE_LT_L_Z;
lower->params[id_INIT_L20] = Property(LUT_D0, 4);
ci.movePortTo(id_OUT, lower, id_OUT);
l2t4_created++;
// Reconnect net
NetInfo *ci_out_conn = ctx->createNet(ctx->idf("%s$out", ci.name.c_str(ctx)));
ci.connectPort(id_OUT, ci_out_conn);
lower->ports[id_COMBIN].name = id_COMBIN;
lower->ports[id_COMBIN].type = PORT_IN;
lower->connectPort(id_COMBIN, ci_out_conn);
dff->disconnectPort(id_DIN);
dff->connectPort(id_DIN, ci_out_conn);
// Attach if only remaining cell is FF
CellInfo *other = net_only_drives(ctx, o, is_dff, id_D, true);
if (other && are_ffs_compatible(dff, other)) {
merge_dff(ci, other);
other->constr_abs_z = true;
other->constr_z = 3;
}
}
}
}
}
@ -300,16 +361,8 @@ void GateMatePacker::pack_cpe()
NetInfo *o = ci.getPort(id_OUT);
if (o) {
CellInfo *dff = net_only_drives(ctx, o, is_dff, id_D, true);
if (dff) {
dff->cluster = ci.name;
dff->constr_abs_z = false;
dff->constr_z = +2;
ci.constr_children.push_back(dff);
dff->renamePort(id_D, id_DIN);
dff->renamePort(id_Q, id_DOUT);
dff->type = (dff->type == id_CC_DLT) ? id_CPE_LATCH : id_CPE_FF;
ff_created++;
}
if (dff)
merge_dff(ci, dff);
}
}
mux_list.clear();
@ -490,17 +543,7 @@ void GateMatePacker::pack_addf()
NetInfo *o = cell->getPort(port);
if (o) {
CellInfo *dff = net_only_drives(ctx, o, is_dff, id_D, true);
if (dff) {
if (other) {
if (dff->getPort(id_CLK) != other->getPort(id_CLK))
return nullptr;
if (dff->getPort(id_EN) != other->getPort(id_EN))
return nullptr;
if (dff->getPort(id_SR) != other->getPort(id_SR))
return nullptr;
if (uarch->get_dff_config(dff) != uarch->get_dff_config(other))
return nullptr;
}
if (dff && are_ffs_compatible(dff, other)) {
dff->cluster = cell->cluster;
dff->constr_abs_z = false;
dff->constr_z = +2;
@ -670,7 +713,7 @@ void GateMatePacker::pack_addf()
if (l2t4_created)
log_info(" %6d L2T4s created\n", l2t4_created);
if (ff_created)
log_info(" %6d DFFs created\n", ff_created);
log_info(" %6d FFs created\n", ff_created);
if (lut2_merged)
log_info(" %6d LUT2s removed\n", lut2_merged);
}