Merge pull request #5209 from povik/hieropt

Start `opt_hier` to enable hierarchical optimization

Author: povik

docs/source/code_examples/macro_commands/opt.ys

@@ -9,6 +9,7 @@ do
     opt_merge
     opt_share  (-full only)
     opt_dff  (except when called with -noff)
+    opt_hier (-hier only)
     opt_clean
     opt_expr
 while <changed design>

docs/source/using_yosys/synthesis/opt.rst

@@ -192,6 +192,13 @@ control inputs.
 Called with ``-nodffe`` and ``-nosdff``, this pass is used to prepare a design
 for :doc:`/using_yosys/synthesis/fsm`.
 
+Hierarchical optimization - `opt_hier` pass
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+
+This pass considers the design hierarchy and propagates unused signals, constant
+signals, and tied-together signals across module boundaries to facilitate
+optimization by other passes.
+
 Removing unused cells and wires - `opt_clean` pass
 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
 

passes/opt/Makefile.inc

@@ -11,6 +11,7 @@ OBJS += passes/opt/opt_dff.o
 OBJS += passes/opt/opt_share.o
 OBJS += passes/opt/opt_clean.o
 OBJS += passes/opt/opt_expr.o
+OBJS += passes/opt/opt_hier.o
 
 ifneq ($(SMALL),1)
 OBJS += passes/opt/share.o

passes/opt/opt.cc

@@ -46,6 +46,7 @@ struct OptPass : public Pass {
 		log("        opt_merge [-share_all]\n");
 		log("        opt_share  (-full only)\n");
 		log("        opt_dff [-nodffe] [-nosdff] [-keepdc] [-sat]  (except when called with -noff)\n");
+		log("        opt_hier (-hier only)\n");
 		log("        opt_clean [-purge]\n");
 		log("        opt_expr [-mux_undef] [-mux_bool] [-undriven] [-noclkinv] [-fine] [-full] [-keepdc]\n");
 		log("    while <changed design>\n");
@@ -56,6 +57,7 @@ struct OptPass : public Pass {
 		log("        opt_expr [-mux_undef] [-mux_bool] [-undriven] [-noclkinv] [-fine] [-full] [-keepdc]\n");
 		log("        opt_merge [-share_all]\n");
 		log("        opt_dff [-nodffe] [-nosdff] [-keepdc] [-sat]  (except when called with -noff)\n");
+		log("        opt_hier (-hier only)\n");
 		log("        opt_clean [-purge]\n");
 		log("    while <changed design in opt_dff>\n");
 		log("\n");
@@ -74,6 +76,7 @@ struct OptPass : public Pass {
 		bool opt_share = false;
 		bool fast_mode = false;
 		bool noff_mode = false;
+		bool hier_mode = false;
 
 		log_header(design, "Executing OPT pass (performing simple optimizations).\n");
 		log_push();
@@ -141,6 +144,10 @@ struct OptPass : public Pass {
 				noff_mode = true;
 				continue;
 			}
+			if (args[argidx] == "-hier") {
+				hier_mode = true;
+				continue;
+			}
 			break;
 		}
 		extra_args(args, argidx, design);
@@ -155,6 +162,8 @@ struct OptPass : public Pass {
 					Pass::call(design, "opt_dff" + opt_dff_args);
 				if (design->scratchpad_get_bool("opt.did_something") == false)
 					break;
+				if (hier_mode)
+					Pass::call(design, "opt_hier");
 				Pass::call(design, "opt_clean" + opt_clean_args);
 				log_header(design, "Rerunning OPT passes. (Removed registers in this run.)\n");
 			}
@@ -173,6 +182,8 @@ struct OptPass : public Pass {
 					Pass::call(design, "opt_share");
 				if (!noff_mode)
 					Pass::call(design, "opt_dff" + opt_dff_args);
+				if (hier_mode)
+					Pass::call(design, "opt_hier");
 				Pass::call(design, "opt_clean" + opt_clean_args);
 				Pass::call(design, "opt_expr" + opt_expr_args);
 				if (design->scratchpad_get_bool("opt.did_something") == false)