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Merge pull request #6038 from YosysHQ/emil/dfflibmap-fix-resetval

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dfflibmap: fix resetval clobber
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Emil J 2026-07-14 18:41:59 +00:00 • committed by GitHub
commit d4f39588a7
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3 changed files with 69 additions and 3 deletions
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7
passes/techmap/dfflibmap.cc
View file

@ -272,17 +272,18 @@ static void find_cell(std::vector<const LibertyAst *> cells, IdString cell_type,
if (!parse_next_state(cell, ff->find("next_state"), cell_next_pin, cell_next_pol, cell_enable_pin, cell_enable_pol) || (has_enable && (cell_enable_pin.empty() || cell_enable_pol != enapol)))
continue;
bool cell_rstval = rstval;
if (has_reset && !cell_next_pol) {
// next_state is negated
// we later propagate this inversion to the output,
// which requires the negation of the reset value
rstval = !rstval;
cell_rstval = !rstval;
}
if (has_reset && rstval == false) {
if (has_reset && cell_rstval == false) {
if (!parse_pin(cell, ff->find("clear"), cell_rst_pin, cell_rst_pol) || cell_rst_pol != rstpol)
continue;
}
if (has_reset && rstval == true) {
if (has_reset && cell_rstval == true) {
if (!parse_pin(cell, ff->find("preset"), cell_rst_pin, cell_rst_pol) || cell_rst_pol != rstpol)
continue;
}

52
tests/techmap/dfflibmap_resetval_clobber.lib Normal file
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@ -0,0 +1,52 @@
library(test) {
cell (bad_dff) {
area : 1;
ff("IQ", "IQN") {
next_state : "!D"; // Look here
clocked_on : "CLK";
preset : "!RST"; // Look here
}
pin(D) {
direction : input;
}
pin(CLK) {
direction : input;
}
pin(RST) {
direction : input;
}
pin(Q) {
direction: output;
function : "IQ";
}
pin(QN) {
direction: output;
function : "IQN";
}
}
cell (good_dff) {
area : 1;
ff("IQ", "IQN") {
next_state : "D"; // Look here
clocked_on : "CLK";
clear : "RST"; // Look here
}
pin(D) {
direction : input;
}
pin(CLK) {
direction : input;
}
pin(RST) {
direction : input;
}
pin(Q) {
direction: output;
function : "IQ";
}
pin(QN) {
direction: output;
function : "IQN";
}
}
}

13
tests/techmap/dfflibmap_resetval_clobber.ys Normal file
View file

@ -0,0 +1,13 @@
read_verilog -icells <<EOT
module top(input C, D, R, output Q);
$_DFF_PP0_ ff (.C(C), .D(D), .R(R), .Q(Q));
endmodule
EOT
dfflibmap -liberty dfflibmap_resetval_clobber.lib top
read_liberty dfflibmap_resetval_clobber.lib
flatten -noscopeinfo
opt_clean
select -assert-count 1 t:* top %i
select -assert-count 1 t:$_DFF_PP0_ top %i