diff options
Diffstat (limited to 'passes/opt/opt_rmdff.cc')
| -rw-r--r-- | passes/opt/opt_rmdff.cc | 85 |
1 files changed, 75 insertions, 10 deletions
diff --git a/passes/opt/opt_rmdff.cc b/passes/opt/opt_rmdff.cc index 5880254c..eeb992a3 100644 --- a/passes/opt/opt_rmdff.cc +++ b/passes/opt/opt_rmdff.cc @@ -174,8 +174,6 @@ bool handle_dffsr(RTLIL::Module *mod, RTLIL::Cell *cell) cell->unsetParam("\\CLR_POLARITY"); cell->unsetPort("\\SET"); cell->unsetPort("\\CLR"); - - return true; } else { @@ -186,11 +184,12 @@ bool handle_dffsr(RTLIL::Module *mod, RTLIL::Cell *cell) cell->unsetParam("\\CLR_POLARITY"); cell->unsetPort("\\SET"); cell->unsetPort("\\CLR"); - - return true; } + + return true; } - else + + if (!hasreset) { IdString new_type; @@ -207,8 +206,10 @@ bool handle_dffsr(RTLIL::Module *mod, RTLIL::Cell *cell) cell->unsetPort("\\S"); cell->unsetPort("\\R"); - return did_something; + return true; } + + return did_something; } bool handle_dlatch(RTLIL::Module *mod, RTLIL::Cell *dlatch) @@ -259,8 +260,8 @@ delete_dlatch: bool handle_dff(RTLIL::Module *mod, RTLIL::Cell *dff) { - RTLIL::SigSpec sig_d, sig_q, sig_c, sig_r; - RTLIL::Const val_cp, val_rp, val_rv; + RTLIL::SigSpec sig_d, sig_q, sig_c, sig_r, sig_e; + RTLIL::Const val_cp, val_rp, val_rv, val_ep; if (dff->type == "$_FF_") { sig_d = dff->getPort("\\D"); @@ -284,6 +285,16 @@ bool handle_dff(RTLIL::Module *mod, RTLIL::Cell *dff) val_rp = RTLIL::Const(dff->type[7] == 'P', 1); val_rv = RTLIL::Const(dff->type[8] == '1', 1); } + else if (dff->type.substr(0,7) == "$_DFFE_" && dff->type.substr(9) == "_" && + (dff->type[7] == 'N' || dff->type[7] == 'P') && + (dff->type[8] == 'N' || dff->type[8] == 'P')) { + sig_d = dff->getPort("\\D"); + sig_q = dff->getPort("\\Q"); + sig_c = dff->getPort("\\C"); + sig_e = dff->getPort("\\E"); + val_cp = RTLIL::Const(dff->type[7] == 'P', 1); + val_ep = RTLIL::Const(dff->type[8] == 'P', 1); + } else if (dff->type == "$ff") { sig_d = dff->getPort("\\D"); sig_q = dff->getPort("\\Q"); @@ -294,6 +305,14 @@ bool handle_dff(RTLIL::Module *mod, RTLIL::Cell *dff) sig_c = dff->getPort("\\CLK"); val_cp = RTLIL::Const(dff->parameters["\\CLK_POLARITY"].as_bool(), 1); } + else if (dff->type == "$dffe") { + sig_e = dff->getPort("\\EN"); + sig_d = dff->getPort("\\D"); + sig_q = dff->getPort("\\Q"); + sig_c = dff->getPort("\\CLK"); + val_cp = RTLIL::Const(dff->parameters["\\CLK_POLARITY"].as_bool(), 1); + val_ep = RTLIL::Const(dff->parameters["\\EN_POLARITY"].as_bool(), 1); + } else if (dff->type == "$adff") { sig_d = dff->getPort("\\D"); sig_q = dff->getPort("\\Q"); @@ -336,39 +355,60 @@ bool handle_dff(RTLIL::Module *mod, RTLIL::Cell *dff) } } + // If clock is driven by a constant and (i) no reset signal + // (ii) Q has no initial value + // (iii) initial value is same as reset value if (!sig_c.empty() && sig_c.is_fully_const() && (!sig_r.size() || !has_init || val_init == val_rv)) { if (val_rv.bits.size() == 0) val_rv = val_init; + // Q is permanently reset value or initial value mod->connect(sig_q, val_rv); goto delete_dff; } + // If D is fully undefined and reset signal present and (i) Q has no initial value + // (ii) initial value is same as reset value if (sig_d.is_fully_undef() && sig_r.size() && (!has_init || val_init == val_rv)) { + // Q is permanently reset value mod->connect(sig_q, val_rv); goto delete_dff; } + // If D is fully undefined and no reset signal and Q has an initial value if (sig_d.is_fully_undef() && !sig_r.size() && has_init) { + // Q is permanently initial value mod->connect(sig_q, val_init); goto delete_dff; } + // If D is fully constant and (i) no reset signal + // (ii) reset value is same as constant D + // and (a) has no initial value + // (b) initial value same as constant D if (sig_d.is_fully_const() && (!sig_r.size() || val_rv == sig_d.as_const()) && (!has_init || val_init == sig_d.as_const())) { + // Q is permanently D mod->connect(sig_q, sig_d); goto delete_dff; } + // If D input is same as Q output and (i) no reset signal + // (ii) no initial signal + // (iii) initial value is same as reset value if (sig_d == sig_q && (sig_r.empty() || !has_init || val_init == val_rv)) { + // Q is permanently reset value or initial value if (sig_r.size()) mod->connect(sig_q, val_rv); - if (has_init) + else if (has_init) mod->connect(sig_q, val_init); goto delete_dff; } + // If reset signal is present, and is fully constant if (!sig_r.empty() && sig_r.is_fully_const()) { + // If reset value is permanently active or if reset is undefined if (sig_r == val_rp || sig_r.is_fully_undef()) { + // Q is permanently reset value mod->connect(sig_q, val_rv); goto delete_dff; } @@ -388,6 +428,30 @@ bool handle_dff(RTLIL::Module *mod, RTLIL::Cell *dff) dff->unsetPort("\\R"); } + // If enable signal is present, and is fully constant + if (!sig_e.empty() && sig_e.is_fully_const()) + { + // If enable value is permanently inactive + if (sig_e != val_ep) { + // Q is permanently initial value + mod->connect(sig_q, val_init); + goto delete_dff; + } + + log("Removing unused enable from %s (%s) from module %s.\n", log_id(dff), log_id(dff->type), log_id(mod)); + + if (dff->type == "$dffe") { + dff->type = "$dff"; + dff->unsetPort("\\EN"); + dff->unsetParam("\\EN_POLARITY"); + return true; + } + + log_assert(dff->type.substr(0,7) == "$_DFFE_"); + dff->type = stringf("$_DFF_%c_", + dff->type[7]); + dff->unsetPort("\\E"); + } + return false; delete_dff: @@ -488,7 +552,8 @@ struct OptRmdffPass : public Pass { if (cell->type.in("$_FF_", "$_DFF_N_", "$_DFF_P_", "$_DFF_NN0_", "$_DFF_NN1_", "$_DFF_NP0_", "$_DFF_NP1_", "$_DFF_PN0_", "$_DFF_PN1_", "$_DFF_PP0_", "$_DFF_PP1_", - "$ff", "$dff", "$adff")) + "$_DFFE_NN_", "$_DFFE_NP_", "$_DFFE_PN_", "$_DFFE_PP_", + "$ff", "$dff", "$dffe", "$adff")) dff_list.push_back(cell->name); if (cell->type.in("$dlatch", "$_DLATCH_P_", "$_DLATCH_N_")) |