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Add flooring division operator

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The $div and $mod cells use truncating division semantics (rounding
towards 0), as defined by e.g. Verilog. Another rounding mode, flooring
(rounding towards negative infinity), can be used in e.g. VHDL. The
new $divfloor cell provides this flooring division.

This commit also fixes the handling of $div in opt_expr, which was
previously optimized as if it was $divfloor.
This commit is contained in:
Xiretza 2020-04-21 12:51:58 +02:00
parent 17163cf43a
commit edd8ff2c07
No known key found for this signature in database
GPG key ID: 17B78226F7139993
19 changed files with 213 additions and 24 deletions
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2
passes/cmds/stat.cc
View file

@ -109,7 +109,7 @@ struct statdata_t
ID($lut), ID($and), ID($or), ID($xor), ID($xnor),
ID($shl), ID($shr), ID($sshl), ID($sshr), ID($shift), ID($shiftx),
ID($lt), ID($le), ID($eq), ID($ne), ID($eqx), ID($nex), ID($ge), ID($gt),
ID($add), ID($sub), ID($mul), ID($div), ID($mod), ID($modfloor), ID($pow), ID($alu))) {
ID($add), ID($sub), ID($mul), ID($div), ID($mod), ID($divfloor), ID($modfloor), ID($pow), ID($alu))) {
int width_a = cell->hasPort(ID::A) ? GetSize(cell->getPort(ID::A)) : 0;
int width_b = cell->hasPort(ID::B) ? GetSize(cell->getPort(ID::B)) : 0;
int width_y = cell->hasPort(ID::Y) ? GetSize(cell->getPort(ID::Y)) : 0;

1
passes/memory/memory_share.cc
View file

@ -716,6 +716,7 @@ struct MemoryShareWorker
cone_ct.cell_types.erase(ID($mod));
cone_ct.cell_types.erase(ID($div));
cone_ct.cell_types.erase(ID($modfloor));
cone_ct.cell_types.erase(ID($divfloor));
cone_ct.cell_types.erase(ID($pow));
cone_ct.cell_types.erase(ID($shl));
cone_ct.cell_types.erase(ID($shr));

31
passes/opt/opt_expr.cc
View file

@ -864,7 +864,7 @@ void replace_const_cells(RTLIL::Design *design, RTLIL::Module *module, bool cons
skip_fine_alu:
if (cell->type.in(ID($reduce_xor), ID($reduce_xnor), ID($shift), ID($shiftx), ID($shl), ID($shr), ID($sshl), ID($sshr),
ID($lt), ID($le), ID($ge), ID($gt), ID($neg), ID($add), ID($sub), ID($mul), ID($div), ID($mod), ID($modfloor), ID($pow)))
ID($lt), ID($le), ID($ge), ID($gt), ID($neg), ID($add), ID($sub), ID($mul), ID($div), ID($mod), ID($divfloor), ID($modfloor), ID($pow)))
{
RTLIL::SigSpec sig_a = assign_map(cell->getPort(ID::A));
RTLIL::SigSpec sig_b = cell->hasPort(ID::B) ? assign_map(cell->getPort(ID::B)) : RTLIL::SigSpec();
@ -883,7 +883,7 @@ skip_fine_alu:
if (0) {
found_the_x_bit:
cover_list("opt.opt_expr.xbit", "$reduce_xor", "$reduce_xnor", "$shl", "$shr", "$sshl", "$sshr", "$shift", "$shiftx",
"$lt", "$le", "$ge", "$gt", "$neg", "$add", "$sub", "$mul", "$div", "$mod", "$modfloor", "$pow", cell->type.str());
"$lt", "$le", "$ge", "$gt", "$neg", "$add", "$sub", "$mul", "$div", "$mod", "$divfloor", "$modfloor", "$pow", cell->type.str());
if (cell->type.in(ID($reduce_xor), ID($reduce_xnor), ID($lt), ID($le), ID($ge), ID($gt)))
replace_cell(assign_map, module, cell, "x-bit in input", ID::Y, RTLIL::State::Sx);
else
@ -1469,6 +1469,7 @@ skip_identity:
FOLD_2ARG_CELL(mul)
FOLD_2ARG_CELL(div)
FOLD_2ARG_CELL(mod)
FOLD_2ARG_CELL(divfloor)
FOLD_2ARG_CELL(modfloor)
FOLD_2ARG_CELL(pow)
@ -1584,7 +1585,7 @@ skip_identity:
}
}
if (!keepdc && cell->type.in(ID($div), ID($mod), ID($modfloor)))
if (!keepdc && cell->type.in(ID($div), ID($mod), ID($divfloor), ID($modfloor)))
{
bool a_signed = cell->parameters[ID::A_SIGNED].as_bool();
bool b_signed = cell->parameters[ID::B_SIGNED].as_bool();
@ -1613,11 +1614,13 @@ skip_identity:
for (int i = 1; i < (b_signed ? sig_b.size()-1 : sig_b.size()); i++)
if (b_val == (1 << i))
{
if (cell->type == ID($div))
if (cell->type.in(ID($div), ID($divfloor)))
{
cover("opt.opt_expr.div_shift");
log_debug("Replacing divide-by-%d cell `%s' in module `%s' with shift-by-%d.\n",
bool is_truncating = cell->type == ID($div);
log_debug("Replacing %s-divide-by-%d cell `%s' in module `%s' with shift-by-%d.\n",
is_truncating ? "truncating" : "flooring",
b_val, cell->name.c_str(), module->name.c_str(), i);
std::vector<RTLIL::SigBit> new_b = RTLIL::SigSpec(i, 6);
@ -1625,10 +1628,26 @@ skip_identity:
while (GetSize(new_b) > 1 && new_b.back() == RTLIL::State::S0)
new_b.pop_back();
cell->type = ID($shr);
cell->type = ID($sshr);
cell->parameters[ID::B_WIDTH] = GetSize(new_b);
cell->parameters[ID::B_SIGNED] = false;
cell->setPort(ID::B, new_b);
// Truncating division is the same as flooring division, except when
// the result is negative and there is a remainder - then trunc = floor + 1
if (is_truncating && a_signed) {
Wire *flooring = module->addWire(NEW_ID, sig_y.size());
cell->setPort(ID::Y, flooring);
Wire *result_neg = module->addWire(NEW_ID);
module->addXor(NEW_ID, sig_a[sig_a.size()-1], sig_b[sig_b.size()-1], result_neg);
Wire *rem_nonzero = module->addWire(NEW_ID);
module->addReduceOr(NEW_ID, sig_a.extract(0, i), rem_nonzero);
Wire *should_add = module->addWire(NEW_ID);
module->addAnd(NEW_ID, result_neg, rem_nonzero, should_add);
module->addAdd(NEW_ID, flooring, should_add, sig_y);
}
cell->check();
}
else if (cell->type.in(ID($mod), ID($modfloor)))

4
passes/opt/opt_share.cc
View file

@ -103,7 +103,7 @@ bool cell_supported(RTLIL::Cell *cell)
if (sig_bi.is_fully_const() && sig_ci.is_fully_const() && sig_bi == sig_ci)
return true;
} else if (cell->type.in(LOGICAL_OPS, SHIFT_OPS, BITWISE_OPS, RELATIONAL_OPS, ID($add), ID($sub), ID($mul), ID($div), ID($mod), ID($modfloor), ID($concat))) {
} else if (cell->type.in(LOGICAL_OPS, SHIFT_OPS, BITWISE_OPS, RELATIONAL_OPS, ID($add), ID($sub), ID($mul), ID($div), ID($mod), ID($divfloor), ID($modfloor), ID($concat))) {
return true;
}
@ -130,7 +130,7 @@ bool mergeable(RTLIL::Cell *a, RTLIL::Cell *b)
RTLIL::IdString decode_port_semantics(RTLIL::Cell *cell, RTLIL::IdString port_name)
{
if (cell->type.in(ID($lt), ID($le), ID($ge), ID($gt), ID($div), ID($mod), ID($modfloor), ID($concat), SHIFT_OPS) && port_name == ID::B)
if (cell->type.in(ID($lt), ID($le), ID($ge), ID($gt), ID($div), ID($mod), ID($divfloor), ID($modfloor), ID($concat), SHIFT_OPS) && port_name == ID::B)
return port_name;
return "";

4
passes/opt/share.cc
View file

@ -376,7 +376,7 @@ struct ShareWorker
continue;
}
if (cell->type.in(ID($mul), ID($div), ID($mod), ID($modfloor))) {
if (cell->type.in(ID($mul), ID($div), ID($mod), ID($divfloor), ID($modfloor))) {
if (config.opt_aggressive || cell->parameters.at(ID::Y_WIDTH).as_int() >= 4)
shareable_cells.insert(cell);
continue;
@ -1134,6 +1134,7 @@ struct ShareWorker
cone_ct.cell_types.erase(ID($mod));
cone_ct.cell_types.erase(ID($div));
cone_ct.cell_types.erase(ID($modfloor));
cone_ct.cell_types.erase(ID($divfloor));
cone_ct.cell_types.erase(ID($pow));
cone_ct.cell_types.erase(ID($shl));
cone_ct.cell_types.erase(ID($shr));
@ -1513,6 +1514,7 @@ struct SharePass : public Pass {
config.generic_bin_ops.insert(ID($sub));
config.generic_bin_ops.insert(ID($div));
config.generic_bin_ops.insert(ID($mod));
config.generic_bin_ops.insert(ID($divfloor));
config.generic_bin_ops.insert(ID($modfloor));
// config.generic_bin_ops.insert(ID($pow));

4
passes/opt/wreduce.cc
View file

@ -37,7 +37,7 @@ struct WreduceConfig
ID($and), ID($or), ID($xor), ID($xnor),
ID($shl), ID($shr), ID($sshl), ID($sshr), ID($shift), ID($shiftx),
ID($lt), ID($le), ID($eq), ID($ne), ID($eqx), ID($nex), ID($ge), ID($gt),
ID($add), ID($sub), ID($mul), // ID($div), ID($mod), ID($modfloor), ID($pow),
ID($add), ID($sub), ID($mul), // ID($div), ID($mod), ID($divfloor), ID($modfloor), ID($pow),
ID($mux), ID($pmux),
ID($dff), ID($adff)
});
@ -545,7 +545,7 @@ struct WreducePass : public Pass {
}
}
if (c->type.in(ID($div), ID($mod), ID($modfloor), ID($pow)))
if (c->type.in(ID($div), ID($mod), ID($divfloor), ID($modfloor), ID($pow)))
{
SigSpec A = c->getPort(ID::A);
int original_a_width = GetSize(A);

3
passes/tests/test_cell.cc
View file

@ -264,7 +264,7 @@ static void create_gold_module(RTLIL::Design *design, RTLIL::IdString cell_type,
cell->setPort(ID::Y, wire);
}
if (muxdiv && cell_type.in(ID($div), ID($mod), ID($modfloor))) {
if (muxdiv && cell_type.in(ID($div), ID($mod), ID($divfloor), ID($modfloor))) {
auto b_not_zero = module->ReduceBool(NEW_ID, cell->getPort(ID::B));
auto div_out = module->addWire(NEW_ID, GetSize(cell->getPort(ID::Y)));
module->addMux(NEW_ID, RTLIL::SigSpec(0, GetSize(div_out)), div_out, b_not_zero, cell->getPort(ID::Y));
@ -839,6 +839,7 @@ struct TestCellPass : public Pass {
cell_types[ID($mul)] = "ABSY";
cell_types[ID($div)] = "ABSY";
cell_types[ID($mod)] = "ABSY";
cell_types[ID($divfloor)] = "ABSY";
cell_types[ID($modfloor)] = "ABSY";
// cell_types[ID($pow)] = "ABsY";