From 7b98e46ac352e625be2d8da9b12e7252ed5179d5 Mon Sep 17 00:00:00 2001
From: Clifford Wolf <clifford@clifford.at>
Date: Sun, 20 Jul 2014 11:41:57 +0200
Subject: [PATCH] Added removing of always inactive cells to "share" pass
---
passes/sat/share.cc | 50 +++++++++++++++++++++++++++++++++++++--------
1 file changed, 42 insertions(+), 8 deletions(-)
diff --git a/passes/sat/share.cc b/passes/sat/share.cc
index a1510a599..fd48b9012 100644
--- a/passes/sat/share.cc
+++ b/passes/sat/share.cc
@@ -41,6 +41,8 @@ struct ShareWorker
CellTypes fwd_ct, cone_ct;
ModWalker modwalker;
+ std::set<RTLIL::Cell*> cells_to_remove;
+
// ------------------------------------------------------------------------------
// Find terminal bits -- i.e. bits that do not (exclusively) feed into a mux tree
@@ -229,7 +231,7 @@ struct ShareWorker
std::map<RTLIL::Cell*, std::set<std::pair<RTLIL::SigSpec, RTLIL::Const>>> activation_patterns_cache;
- bool sort_check_pattern(std::pair<RTLIL::SigSpec, RTLIL::Const> &p)
+ bool sort_check_activation_pattern(std::pair<RTLIL::SigSpec, RTLIL::Const> &p)
{
std::map<RTLIL::SigBit, RTLIL::State> p_bits;
@@ -253,7 +255,13 @@ struct ShareWorker
return true;
}
- const std::set<std::pair<RTLIL::SigSpec, RTLIL::Const>> &find_cell_activation_patterns(RTLIL::Cell *cell)
+ void optimize_activation_patterns(std::set<std::pair<RTLIL::SigSpec, RTLIL::Const>> & /* patterns */)
+ {
+ // TODO: Remove patterns that are contained in other patterns
+ // TODO: Consolidate pairs of patterns that only differ in the value for one signal bit
+ }
+
+ const std::set<std::pair<RTLIL::SigSpec, RTLIL::Const>> &find_cell_activation_patterns(RTLIL::Cell *cell, const char *indent)
{
if (activation_patterns_cache.count(cell))
return activation_patterns_cache.at(cell);
@@ -276,7 +284,7 @@ struct ShareWorker
for (auto c : driven_cells)
{
- const std::set<std::pair<RTLIL::SigSpec, RTLIL::Const>> &c_patterns = find_cell_activation_patterns(c);
+ const std::set<std::pair<RTLIL::SigSpec, RTLIL::Const>> &c_patterns = find_cell_activation_patterns(c, indent);
if (c->type == "$mux" || c->type == "$pmux")
{
@@ -300,14 +308,14 @@ struct ShareWorker
for (auto p : c_patterns) {
for (int i = 0; i < SIZE(sig_s); i++)
p.first.append_bit(sig_s[i]), p.second.bits.push_back(RTLIL::State::S0);
- if (sort_check_pattern(p))
+ if (sort_check_activation_pattern(p))
activation_patterns_cache[cell].insert(p);
}
for (int idx : used_in_b_parts)
for (auto p : c_patterns) {
p.first.append_bit(sig_s[idx]), p.second.bits.push_back(RTLIL::State::S1);
- if (sort_check_pattern(p))
+ if (sort_check_activation_pattern(p))
activation_patterns_cache[cell].insert(p);
}
}
@@ -319,6 +327,12 @@ struct ShareWorker
}
}
+ optimize_activation_patterns(activation_patterns_cache[cell]);
+ if (activation_patterns_cache[cell].empty()) {
+ log("%sFound cell that is never activated: %s\n", indent, log_id(cell));
+ cells_to_remove.insert(cell);
+ }
+
return activation_patterns_cache[cell];
}
@@ -375,9 +389,14 @@ struct ShareWorker
log(" Analyzing resource sharing options for %s:\n", log_id(cell));
- const std::set<std::pair<RTLIL::SigSpec, RTLIL::Const>> &cell_activation_patterns = find_cell_activation_patterns(cell);
+ const std::set<std::pair<RTLIL::SigSpec, RTLIL::Const>> &cell_activation_patterns = find_cell_activation_patterns(cell, " ");
RTLIL::SigSpec cell_activation_signals = bits_from_activation_patterns(cell_activation_patterns);
+ if (cell_activation_patterns.empty()) {
+ log (" Cell is never active. Sharing is pointless, we simply remove it.\n");
+ continue;
+ }
+
if (cell_activation_patterns.count(std::pair<RTLIL::SigSpec, RTLIL::Const>())) {
log (" Cell is always active. Therefore no sharing is possible.\n");
continue;
@@ -402,11 +421,17 @@ struct ShareWorker
{
log(" Analyzing resource sharing with %s:\n", log_id(other_cell));
- const std::set<std::pair<RTLIL::SigSpec, RTLIL::Const>> &other_cell_activation_patterns = find_cell_activation_patterns(other_cell);
+ const std::set<std::pair<RTLIL::SigSpec, RTLIL::Const>> &other_cell_activation_patterns = find_cell_activation_patterns(other_cell, " ");
RTLIL::SigSpec other_cell_activation_signals = bits_from_activation_patterns(other_cell_activation_patterns);
+ if (other_cell_activation_patterns.empty()) {
+ log (" Cell is never active. Sharing is pointless, we simply remove it.\n");
+ shareable_cells.erase(other_cell);
+ continue;
+ }
+
if (other_cell_activation_patterns.count(std::pair<RTLIL::SigSpec, RTLIL::Const>())) {
- log (" Cell is always active. Therefore no sharing is possible.\n");
+ log (" Cell is always active. Therefore no sharing is possible.\n");
continue;
}
@@ -484,6 +509,15 @@ struct ShareWorker
break;
}
}
+
+ if (!cells_to_remove.empty()) {
+ log("Removing %d cells in module %s:\n", SIZE(cells_to_remove), log_id(module));
+ for (auto c : cells_to_remove) {
+ log(" Removing cell %s (%s).\n", log_id(c), log_id(c->type));
+ module->cells.erase(c->name);
+ delete c;
+ }
+ }
}
};