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Add flooring modulo 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 $modfloor cell provides this flooring modulo (also known as "remainder"
in several languages, but this name is ambiguous).

This commit also fixes the handling of $mod in opt_expr, which was
previously optimized as if it was $modfloor.
This commit is contained in:
Xiretza 2020-04-08 19:30:47 +02:00
parent 0d99522b3c
commit 17163cf43a
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GPG key ID: 17B78226F7139993
23 changed files with 280 additions and 37 deletions
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3
passes/tests/test_cell.cc
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@ -264,7 +264,7 @@ static void create_gold_module(RTLIL::Design *design, RTLIL::IdString cell_type,
cell->setPort(ID::Y, wire);
}
if (muxdiv && cell_type.in(ID($div), ID($mod))) {
if (muxdiv && cell_type.in(ID($div), ID($mod), ID($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($mod)] = "ABSY";
cell_types[ID($modfloor)] = "ABSY";
// cell_types[ID($pow)] = "ABsY";
cell_types[ID($logic_not)] = "ASY";