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Fix muxadd peepopt to track bitsplit

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This commit is contained in:
Akash Levy 2024-09-27 02:28:32 -07:00
parent b1383a80cf
commit 7f05f0b273
1 changed files with 17 additions and 4 deletions
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21
passes/pmgen/peepopt_muxadd.pmg
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@ -4,39 +4,52 @@ pattern muxadd
// y = s ? (a + b) : a ===> y = a + (s ? b : 0)
//
state <SigSpec> add_y add_a add_b
state <SigSpec> add_a add_b add_y
match add
// Select adder
select add->type == $add
endmatch
code add_y add_a add_b
add_y = port(add, \Y);
// Get adder signals
add_a = port(add, \A);
add_b = port(add, \B);
add_y = port(add, \Y);
// Fanout of each adder Y bit should be 1 (no bit-split)
for (auto bit : add_y)
if (nusers(bit) != 2)
reject;
// A and B can be interchanged
branch;
std::swap(add_a, add_b);
endcode
match mux
// Select mux of form s ? (a + b) : a, allow leading 0s when A_WIDTH != Y_WIDTH
select mux->type == $mux
index <SigSpec> port(mux, \A) === SigSpec({Const(State::S0, GetSize(add_y)-GetSize(add_a)), add_a})
index <SigSpec> port(mux, \B) === add_y
endmatch
code
// Get mux signal
SigSpec mux_y = port(mux, \Y);
// Create new mid wire
SigSpec mid = module->addWire(NEW_ID, GetSize(add_b));
// Rewire
mux->setPort(\A, Const(State::S0, GetSize(add_b)));
mux->setPort(\B, add_b);
mux->setPort(\Y, mid);
add->setPort(\B, mid);
add->setPort(\Y, mux_y);
// Log, fixup, accept
log("muxadd pattern in %s: mux=%s, add=%s\n", log_id(module), log_id(mux), log_id(add));
mux->fixup_parameters();
accept;
endcode