Merge remote-tracking branch 'origin/eddie/peepopt_dffmuxext' into xc7dsp

passes/pmgen/Makefile.inc

@@ -33,6 +33,7 @@ $(eval $(call add_extra_objs,passes/pmgen/peepopt_pm.h))
 
 PEEPOPT_PATTERN  = passes/pmgen/peepopt_shiftmul.pmg
 PEEPOPT_PATTERN += passes/pmgen/peepopt_muldiv.pmg
+PEEPOPT_PATTERN += passes/pmgen/peepopt_dffmuxext.pmg
 
 passes/pmgen/peepopt_pm.h: passes/pmgen/pmgen.py $(PEEPOPT_PATTERN)
 	$(P) mkdir -p passes/pmgen && python3 $< -o $@ -p peepopt $(filter-out $<,$^)

passes/pmgen/peepopt.cc

@@ -60,6 +60,7 @@ struct PeepoptPass : public Pass {
 				peepopt_pm pm(module, module->selected_cells());
 				pm.run_shiftmul();
 				pm.run_muldiv();
+				pm.run_dffmuxext();
 			}
 		}
 	}

passes/pmgen/peepopt_dffmuxext.pmg

@@ -0,0 +1,58 @@
+pattern dffmuxext
+
+state <IdString> muxAB
+
+match dff
+	select dff->type == $dff
+	select GetSize(port(dff, \D)) > 1
+endmatch
+
+match mux
+	select mux->type == $mux
+	select GetSize(port(mux, \Y)) > 1
+	choice <IdString> AB {\A, \B}
+	//select port(mux, AB)[GetSize(port(mux, \Y))-1].wire
+	index <SigSpec> port(mux, \Y) === port(dff, \D)
+	define <IdString> BA (AB == \A ? \B : \A)
+	index <SigSpec> port(mux, BA) === port(dff, \Q)
+	filter port(mux, AB)[GetSize(port(mux, \Y))-1] == port(mux, AB)[GetSize(port(mux, \Y))-2]
+	set muxAB AB
+endmatch
+
+code
+	did_something = true;
+
+	log_cell(dff);
+	log_cell(mux);
+
+	SigSpec &D = mux->connections_.at(muxAB);
+	SigSpec &Q = dff->connections_.at(\Q);
+	int width = GetSize(D);
+
+	SigBit sign = D[width-1];
+	bool is_signed = sign.wire;
+	int i;
+	for (i = width-1; i >= 2; i--) {
+		if (!is_signed) {
+			module->connect(Q[i], sign);
+			if (D[i-1] != sign)
+				break;
+		}
+		else {
+			module->connect(Q[i], Q[i-1]);
+			if (D[i-2] != sign)
+				break;
+		}
+	}
+
+	mux->connections_.at(\A).remove(i, width-i);
+	mux->connections_.at(\B).remove(i, width-i);
+	mux->connections_.at(\Y).remove(i, width-i);
+	mux->fixup_parameters();
+	dff->connections_.at(\D).remove(i, width-i);
+	dff->connections_.at(\Q).remove(i, width-i);
+	dff->fixup_parameters();
+
+	log("dffmuxext pattern in %s: dff=%s, mux=%s; removed top %d bits.\n", log_id(module), log_id(dff), log_id(mux), width-i);
+	accept;
+endcode

tests/simple/peepopt.v

@@ -11,3 +11,11 @@ wire [3:0] t;
 assign t = i * 3;
 assign o = t / 3;
 endmodule
+
+module peepopt_dffmuxext_signed(input clk, ce, input signed [1:0] i, output reg signed [3:0] o);
+    always @(posedge clk) if (ce) o <= i;
+endmodule
+
+module peepopt_dffmuxext_unsigned(input clk, ce, input [1:0] i, output reg [3:0] o);
+    always @(posedge clk) if (ce) o <= i;
+endmodule