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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 $modfloor.
This commit is contained in:
Xiretza 2020-04-08 19:30:47 +02:00
parent 0d99522b3c
commit 17163cf43a
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GPG key ID: 17B78226F7139993
23 changed files with 280 additions and 37 deletions
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5
backends/smv/smv.cc
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@ -358,7 +358,8 @@ struct SmvWorker
continue;
}
if (cell->type.in(ID($div), ID($mod)))
// SMV has a "mod" operator, but its semantics don't seem to be well-defined - to be safe, don't generate it at all
if (cell->type.in(ID($div)/*, ID($mod), ID($modfloor)*/))
{
int width_y = GetSize(cell->getPort(ID::Y));
int width = max(width_y, GetSize(cell->getPort(ID::A)));
@ -366,7 +367,7 @@ struct SmvWorker
string expr_a, expr_b, op;
if (cell->type == ID($div)) op = "/";
if (cell->type == ID($mod)) op = "mod";
//if (cell->type == ID($mod)) op = "mod";
if (cell->getParam(ID::A_SIGNED).as_bool())
{

4
backends/smv/test_cells.sh
View file

@ -7,8 +7,8 @@ mkdir -p test_cells.tmp
cd test_cells.tmp
# don't test $mul to reduce runtime
# don't test $div and $mod to reduce runtime and avoid "div by zero" message
../../../yosys -p 'test_cell -n 5 -w test all /$alu /$fa /$lcu /$lut /$macc /$mul /$div /$mod'
# don't test $div/$mod/$modfloor to reduce runtime and avoid "div by zero" message
../../../yosys -p 'test_cell -n 5 -w test all /$alu /$fa /$lcu /$lut /$macc /$mul /$div /$mod /$modfloor'
cat > template.txt << "EOT"
%module main