From 6041f780c31525c1fc4d34b95317d7946466957b Mon Sep 17 00:00:00 2001
From: Clifford Wolf <clifford@clifford.at>
Date: Tue, 5 Apr 2016 12:51:04 +0200
Subject: [PATCH] Prefer noninverting FFs in dfflibmap
---
passes/techmap/dfflibmap.cc | 24 ++++++++++++++++++++----
1 file changed, 20 insertions(+), 4 deletions(-)
diff --git a/passes/techmap/dfflibmap.cc b/passes/techmap/dfflibmap.cc
index 4d7a1a704..3195e5a78 100644
--- a/passes/techmap/dfflibmap.cc
+++ b/passes/techmap/dfflibmap.cc
@@ -108,6 +108,7 @@ static void find_cell(LibertyAst *ast, std::string cell_type, bool clkpol, bool
LibertyAst *best_cell = NULL;
std::map<std::string, char> best_cell_ports;
int best_cell_pins = 0;
+ bool best_cell_noninv = false;
double best_cell_area = 0;
if (ast->id != "library")
@@ -155,6 +156,7 @@ static void find_cell(LibertyAst *ast, std::string cell_type, bool clkpol, bool
int num_pins = 0;
bool found_output = false;
+ bool found_noninv_output = false;
for (auto pin : cell->children)
{
if (pin->id != "pin" || pin->args.size() != 1)
@@ -175,10 +177,14 @@ static void find_cell(LibertyAst *ast, std::string cell_type, bool clkpol, bool
value.erase(pos, 1);
if (value == ff->args[0]) {
this_cell_ports[pin->args[0]] = cell_next_pol ? 'Q' : 'q';
+ if (cell_next_pol)
+ found_noninv_output = true;
found_output = true;
} else
if (value == ff->args[1]) {
this_cell_ports[pin->args[0]] = cell_next_pol ? 'q' : 'Q';
+ if (!cell_next_pol)
+ found_noninv_output = true;
found_output = true;
}
}
@@ -187,7 +193,7 @@ static void find_cell(LibertyAst *ast, std::string cell_type, bool clkpol, bool
this_cell_ports[pin->args[0]] = 0;
}
- if (!found_output || (best_cell != NULL && num_pins > best_cell_pins))
+ if (!found_output || (best_cell != NULL && (num_pins > best_cell_pins || (best_cell_noninv && !found_noninv_output))))
continue;
if (best_cell != NULL && num_pins == best_cell_pins && area > best_cell_area)
@@ -196,12 +202,14 @@ static void find_cell(LibertyAst *ast, std::string cell_type, bool clkpol, bool
best_cell = cell;
best_cell_pins = num_pins;
best_cell_area = area;
+ best_cell_noninv = found_noninv_output;
best_cell_ports.swap(this_cell_ports);
continue_cell_loop:;
}
if (best_cell != NULL) {
- log(" cell %s (pins=%d, area=%.2f) is a direct match for cell type %s.\n", best_cell->args[0].c_str(), best_cell_pins, best_cell_area, cell_type.c_str());
+ log(" cell %s (%sinv, pins=%d, area=%.2f) is a direct match for cell type %s.\n",
+ best_cell->args[0].c_str(), best_cell_noninv ? "non" : "", best_cell_pins, best_cell_area, cell_type.c_str());
if (prepare_mode) {
cell_mappings[cell_type].cell_name = cell_type;
cell_mappings[cell_type].ports["C"] = 'C';
@@ -221,6 +229,7 @@ static void find_cell_sr(LibertyAst *ast, std::string cell_type, bool clkpol, bo
LibertyAst *best_cell = NULL;
std::map<std::string, char> best_cell_ports;
int best_cell_pins = 0;
+ bool best_cell_noninv = false;
double best_cell_area = 0;
if (ast->id != "library")
@@ -260,6 +269,7 @@ static void find_cell_sr(LibertyAst *ast, std::string cell_type, bool clkpol, bo
int num_pins = 0;
bool found_output = false;
+ bool found_noninv_output = false;
for (auto pin : cell->children)
{
if (pin->id != "pin" || pin->args.size() != 1)
@@ -280,10 +290,14 @@ static void find_cell_sr(LibertyAst *ast, std::string cell_type, bool clkpol, bo
value.erase(pos, 1);
if (value == ff->args[0]) {
this_cell_ports[pin->args[0]] = cell_next_pol ? 'Q' : 'q';
+ if (cell_next_pol)
+ found_noninv_output = true;
found_output = true;
} else
if (value == ff->args[1]) {
this_cell_ports[pin->args[0]] = cell_next_pol ? 'q' : 'Q';
+ if (!cell_next_pol)
+ found_noninv_output = true;
found_output = true;
}
}
@@ -292,7 +306,7 @@ static void find_cell_sr(LibertyAst *ast, std::string cell_type, bool clkpol, bo
this_cell_ports[pin->args[0]] = 0;
}
- if (!found_output || (best_cell != NULL && num_pins > best_cell_pins))
+ if (!found_output || (best_cell != NULL && (num_pins > best_cell_pins || (best_cell_noninv && !found_noninv_output))))
continue;
if (best_cell != NULL && num_pins == best_cell_pins && area > best_cell_area)
@@ -301,12 +315,14 @@ static void find_cell_sr(LibertyAst *ast, std::string cell_type, bool clkpol, bo
best_cell = cell;
best_cell_pins = num_pins;
best_cell_area = area;
+ best_cell_noninv = found_noninv_output;
best_cell_ports.swap(this_cell_ports);
continue_cell_loop:;
}
if (best_cell != NULL) {
- log(" cell %s (pins=%d, area=%.2f) is a direct match for cell type %s.\n", best_cell->args[0].c_str(), best_cell_pins, best_cell_area, cell_type.c_str());
+ log(" cell %s (%sinv, pins=%d, area=%.2f) is a direct match for cell type %s.\n",
+ best_cell->args[0].c_str(), best_cell_noninv ? "non" : "", best_cell_pins, best_cell_area, cell_type.c_str());
if (prepare_mode) {
cell_mappings[cell_type].cell_name = cell_type;
cell_mappings[cell_type].ports["C"] = 'C';