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Support external fanout for addsub_c

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This commit is contained in:
Akash Levy 2025-09-11 03:48:14 -07:00
parent ccf3909982
commit c1557950ef
2 changed files with 21 additions and 18 deletions
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22
passes/opt/peepopt_addsub_c.pmg
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@ -18,10 +18,6 @@ code a b_const addsub1_y
b_const = port(addsub1, \B);
addsub1_y = port(addsub1, \Y);
// Fanout of each add/sub Y bit should be 1 (no bit-split)
if (nusers(addsub1_y) != 2)
reject;
// A and B can be interchanged for adder
if (addsub1->type == $add) {
branch;
@ -40,6 +36,9 @@ match addsub2
endmatch
code
// New addsub1 cell (will be reused unless there is external fanout)
auto cell = addsub1;
// Get addsub2 signals
SigSpec addsub2_a = port(addsub2, \A);
SigSpec c_const = port(addsub2, \B);
@ -114,16 +113,21 @@ code
if (offset < 0 || !addsub2_a.extract(0, offset).is_fully_zero())
reject;
// Rewire to only keep addsub1
addsub1->setPort(\A, a);
addsub1->setPort(\B, const_value);
addsub1->setPort(\Y, addsub2_y);
// Reuse/create new cell to drive the rewritten equation
if (nusers(addsub1_y) != 2) {
cell = module->addCell(NEW_ID2_SUFFIX("asconst"), addsub1->type);
cell->attributes = addsub1->attributes;
cell->parameters = addsub1->parameters;
}
cell->setPort(\A, a);
cell->setPort(\B, const_value);
cell->setPort(\Y, addsub2_y);
// Remove addsub2
autoremove(addsub2);
// Log, fixup, accept
log("addsub_const pattern in %s: addsub1=%s, addsub2=%s\n", log_id(module), log_id(addsub1), log_id(addsub2));
addsub1->fixup_parameters();
cell->fixup_parameters();
accept;
endcode