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dfflibmap: pass selection to dfflegalize #5729

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dfflibmap: pass selection to dfflegalize #5729

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2 changes: 2 additions & 0 deletions passes/techmap/dfflibmap.cc
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Original file line number Diff line number Diff line change
Expand Up @@ -694,6 +694,8 @@ struct DfflibmapPass : public Pass {
for (auto it : cell_mappings)
dfflegalize_cmd += stringf(" -cell %s 01", it.first);
dfflegalize_cmd += " t:$_DFF* t:$_SDFF*";
for (auto module : design->selected_modules())
dfflegalize_cmd += " " + module -> name.str();
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@KrystalDelusion KrystalDelusion Mar 8, 2026

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This ain't it. Not only does this expand partially selected modules into fully selected modules, but it is still selecting all t:$_DFF* t:$_SDFF*, making this actively worse and causing failures if the design contains any other types of flop (raising an error in dfflegalize).

My current thought is running through all the currently selected cells, pushing them to a new selection if they are the right type, and then using Pass::call_on_selection() with the new selection. Or doing % t:$_DFF* t:$_SDFF* %u %i might work, but that's starting to get messy in terms of readability.

if (info_mode) {
log("dfflegalize command line: %s\n", dfflegalize_cmd);
} else {
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11 changes: 11 additions & 0 deletions tests/techmap/dfflibmap.ys
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Expand Up @@ -97,3 +97,14 @@ select -assert-count 1 t:dffe
# but we have to invert it because the CLEAR pin is active low.
# ff2.CLEAR = !R
select -assert-count 1 c:ff2 %x:+[CLEAR] %ci t:$_NOT_ %i

# Test that dfflibmap respects selection and doesn't run dfflegalize on unselected modules
design -load orig
copy top top_unmapped
dfflibmap -liberty dfflibmap.lib top
# top should be mapped
select -module top -assert-count 1 t:dffn
# top_unmapped should have no mapped cells
select -module top_unmapped -assert-none t:dffn
select -module top_unmapped -assert-none t:dffe
select -module top_unmapped -assert-none t:dffsr
Comment on lines +108 to +110
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@KrystalDelusion KrystalDelusion Mar 8, 2026

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Test dfflegalize isn't running, not dfflibmap.

Suggested change
select -module top_unmapped -assert-none t:dffn
select -module top_unmapped -assert-none t:dffe
select -module top_unmapped -assert-none t:dffsr
select -module top_unmapped -assert-count 1 t:$_DFFE_PP_
select -module top_unmapped -assert-none t:$_DFF_N_