From d3b1a29708fc9cfd793180763484125a5f978d1a Mon Sep 17 00:00:00 2001
From: Clifford Wolf <clifford@clifford.at>
Date: Tue, 5 Aug 2014 13:11:04 +0200
Subject: [PATCH] Cleanups and improvements in wreduce pass
---
passes/cmds/wreduce.cc | 128 +++++++++++++++++++++++++----------------
1 file changed, 79 insertions(+), 49 deletions(-)
diff --git a/passes/cmds/wreduce.cc b/passes/cmds/wreduce.cc
index b90843ef9..ce24e09b2 100644
--- a/passes/cmds/wreduce.cc
+++ b/passes/cmds/wreduce.cc
@@ -61,8 +61,10 @@ struct WreduceWorker
WreduceWorker(WreduceConfig *config, Module *module) :
config(config), module(module), mi(module) { }
- void run_cell_mux(Cell *cell)
+ bool run_cell_mux(Cell *cell)
{
+ // Reduce size of MUX if inputs agree on a value for a bit or a output bit is unused
+
SigSpec sig_a = mi.sigmap(cell->getPort("\\A"));
SigSpec sig_b = mi.sigmap(cell->getPort("\\B"));
SigSpec sig_s = mi.sigmap(cell->getPort("\\S"));
@@ -90,49 +92,60 @@ struct WreduceWorker
bits_removed.push_back(ref);
}
- if (!bits_removed.empty())
- {
- SigSpec sig_removed;
- for (int i = SIZE(bits_removed)-1; i >= 0; i--)
- sig_removed.append_bit(bits_removed[i]);
+ if (bits_removed.empty())
+ return false;
- log("Removed top %d bits (of %d) from mux cell %s.%s (%s).\n",
- SIZE(sig_removed), SIZE(sig_y), log_id(module), log_id(cell), log_id(cell->type));
+ SigSpec sig_removed;
+ for (int i = SIZE(bits_removed)-1; i >= 0; i--)
+ sig_removed.append_bit(bits_removed[i]);
- int n_removed = SIZE(sig_removed);
- int n_kept = SIZE(sig_y) - SIZE(sig_removed);
+ log("Removed top %d bits (of %d) from mux cell %s.%s (%s).\n",
+ SIZE(sig_removed), SIZE(sig_y), log_id(module), log_id(cell), log_id(cell->type));
- SigSpec new_work_queue_bits;
- new_work_queue_bits.append(sig_a.extract(n_kept, n_removed));
- new_work_queue_bits.append(sig_y.extract(n_kept, n_removed));
+ int n_removed = SIZE(sig_removed);
+ int n_kept = SIZE(sig_y) - SIZE(sig_removed);
- SigSpec new_sig_a = sig_a.extract(0, n_kept);
- SigSpec new_sig_y = sig_y.extract(0, n_kept);
- SigSpec new_sig_b;
+ SigSpec new_work_queue_bits;
+ new_work_queue_bits.append(sig_a.extract(n_kept, n_removed));
+ new_work_queue_bits.append(sig_y.extract(n_kept, n_removed));
- for (int k = 0; k < SIZE(sig_s); k++) {
- new_sig_b.append(sig_b.extract(k*SIZE(sig_a), n_kept));
- new_work_queue_bits.append(sig_b.extract(k*SIZE(sig_a) + n_kept, n_removed));
- }
+ SigSpec new_sig_a = sig_a.extract(0, n_kept);
+ SigSpec new_sig_y = sig_y.extract(0, n_kept);
+ SigSpec new_sig_b;
- for (auto bit : new_work_queue_bits)
- work_queue_bits.insert(bit);
-
- cell->setPort("\\A", new_sig_a);
- cell->setPort("\\B", new_sig_b);
- cell->setPort("\\Y", new_sig_y);
- cell->fixup_parameters();
-
- module->connect(sig_y.extract(n_kept, n_removed), sig_removed);
+ for (int k = 0; k < SIZE(sig_s); k++) {
+ new_sig_b.append(sig_b.extract(k*SIZE(sig_a), n_kept));
+ new_work_queue_bits.append(sig_b.extract(k*SIZE(sig_a) + n_kept, n_removed));
}
+
+ for (auto bit : new_work_queue_bits)
+ work_queue_bits.insert(bit);
+
+ cell->setPort("\\A", new_sig_a);
+ cell->setPort("\\B", new_sig_b);
+ cell->setPort("\\Y", new_sig_y);
+ cell->fixup_parameters();
+
+ module->connect(sig_y.extract(n_kept, n_removed), sig_removed);
+ return true;
}
- void run_reduce_inport(Cell *cell, char port)
+ bool run_reduce_inport(Cell *cell, char port, int max_port_size)
{
bool is_signed = cell->getParam(stringf("\\%c_SIGNED", port)).as_bool();
SigSpec sig = mi.sigmap(cell->getPort(stringf("\\%c", port)));
+ if (port == 'B' && cell->type.in("$shl", "$shr", "$sshl", "$sshr"))
+ is_signed = false;
+
int bits_removed = 0;
+ if (SIZE(sig) > max_port_size) {
+ bits_removed = SIZE(sig) - max_port_size;
+ for (auto bit : sig.extract(max_port_size, bits_removed))
+ work_queue_bits.insert(bit);
+ sig = sig.extract(0, max_port_size);
+ }
+
if (is_signed) {
while (SIZE(sig) > 1 && constmap(sig[SIZE(sig)-1]) == constmap(sig[SIZE(sig)-2]))
work_queue_bits.insert(sig[SIZE(sig)-1]), sig.remove(SIZE(sig)-1), bits_removed++;
@@ -141,31 +154,44 @@ struct WreduceWorker
work_queue_bits.insert(sig[SIZE(sig)-1]), sig.remove(SIZE(sig)-1), bits_removed++;
}
- if (bits_removed) {
- log("Removed top %d bits (of %d) from port %c of cell %s.%s (%s).\n",
- bits_removed, SIZE(sig) + bits_removed, port, log_id(module), log_id(cell), log_id(cell->type));
- cell->setPort(stringf("\\%c", port), sig);
- }
+ if (bits_removed == 0)
+ return false;
+
+ log("Removed top %d bits (of %d) from port %c of cell %s.%s (%s).\n",
+ bits_removed, SIZE(sig) + bits_removed, port, log_id(module), log_id(cell), log_id(cell->type));
+ cell->setPort(stringf("\\%c", port), sig);
+ return true;
}
- void run_cell(Cell *cell)
+ bool run_cell(Cell *cell)
{
- if (!cell->type.in(config->supported_cell_types))
- return;
+ bool did_something = false;
- if (cell->type.in("$mux", "$pmux", "$safe_pmux")) {
- run_cell_mux(cell);
- return;
+ if (!cell->type.in(config->supported_cell_types))
+ return false;
+
+ if (cell->type.in("$mux", "$pmux", "$safe_pmux"))
+ return run_cell_mux(cell);
+
+
+ // Reduce size of ports A and B based on constant input bits and size of output port
+
+ int max_port_a_size = cell->hasPort("\\A") ? SIZE(cell->getPort("\\A")) : -1;
+ int max_port_b_size = cell->hasPort("\\B") ? SIZE(cell->getPort("\\B")) : -1;
+
+ if (cell->type.in("$not", "$pos", "$bu0", "$neg", "$and", "$or", "$xor", "$add", "$sub")) {
+ max_port_a_size = std::min(max_port_a_size, SIZE(cell->getPort("\\Y")));
+ max_port_b_size = std::min(max_port_b_size, SIZE(cell->getPort("\\Y")));
}
- if (cell->type.in("$shl", "$shr", "$sshl", "$sshr"))
- cell->setParam("\\B_SIGNED", false);
+ if (max_port_a_size >= 0)
+ did_something = run_reduce_inport(cell, 'A', max_port_a_size) || did_something;
- if (cell->hasParam("\\A_SIGNED"))
- run_reduce_inport(cell, 'A');
+ if (max_port_b_size >= 0)
+ did_something = run_reduce_inport(cell, 'B', max_port_b_size) || did_something;
- if (cell->hasParam("\\B_SIGNED"))
- run_reduce_inport(cell, 'B');
+
+ // Reduce size of port Y based on sizes for A and B and unused bits in Y
SigSpec sig = mi.sigmap(cell->getPort("\\Y"));
@@ -208,9 +234,13 @@ struct WreduceWorker
log("Removed top %d bits (of %d) from port Y of cell %s.%s (%s).\n",
bits_removed, SIZE(sig) + bits_removed, log_id(module), log_id(cell), log_id(cell->type));
cell->setPort("\\Y", sig);
+ did_something = true;
}
- cell->fixup_parameters();
+ if (did_something)
+ cell->fixup_parameters();
+
+ return did_something;
}
void run()
@@ -222,7 +252,7 @@ struct WreduceWorker
{
work_queue_bits.clear();
for (auto c : work_queue_cells)
- run_cell(c);
+ while (run_cell(c)) { }
work_queue_cells.clear();
for (auto bit : work_queue_bits)