yosys/tests/techmap/clockgate.ys

read_verilog << EOT

module dffe_00( input clk, en,
			input d1, output reg q1,
		);
	always @( negedge clk ) begin
		if ( ~en )
			q1 <= d1;
	end
endmodule

module dffe_01( input clk, en,
			input d1, output reg q1,
		);
	always @( negedge clk ) begin
		if ( en )
			q1 <= d1;
	end
endmodule

module dffe_10( input clk, en,
			input d1, output reg q1,
		);
	always @( posedge clk ) begin
		if ( ~en )
			q1 <= d1;
	end
endmodule

module dffe_11( input clk, en,
			input d1, output reg q1,
		);
	always @( posedge clk ) begin
		if ( en )
			q1 <= d1;
	end
endmodule

module dffe_wide_11( input clk, en,
			input [3:0] d1, output reg [3:0] q1,
		);
	always @( posedge clk ) begin
		if ( en )
			q1 <= d1;
	end
endmodule

EOT

proc
opt

design -save before

#------------------------------------------------------------------------------

# Test -pos

clockgate -pos pdk_icg ce:clkin:clkout -tie_lo scanen

# falling edge clock flops don't get matched on -pos
select -module dffe_00 -assert-count 0 t:\\pdk_icg
select -module dffe_01 -assert-count 0 t:\\pdk_icg
# falling edge clock flops do get matched on -pos
select -module dffe_10 -assert-count 1 t:\\pdk_icg
select -module dffe_11 -assert-count 1 t:\\pdk_icg
# if necessary, EN is inverted, since the given ICG
# is assumed to have an active-high EN
select -module dffe_10 -assert-count 1 t:\$_NOT_
select -module dffe_11 -assert-count 0 t:\$_NOT_

# Extra credit: multi-bit FFs work fine as well
select -module dffe_wide_11 -assert-count 1 t:\\pdk_icg

#------------------------------------------------------------------------------

# Test -neg

design -load before
clockgate -min_net_size 1 -neg pdk_icg ce:clkin:clkout -tie_lo scanen

# rising edge clock flops don't get matched on -neg
select -module dffe_00 -assert-count 1 t:\\pdk_icg
select -module dffe_01 -assert-count 1 t:\\pdk_icg
# rising edge clock flops do get matched on -neg
select -module dffe_10 -assert-count 0 t:\\pdk_icg
select -module dffe_11 -assert-count 0 t:\\pdk_icg
# if necessary, EN is inverted, since the given ICG
# is assumed to have an active-high EN
select -module dffe_00 -assert-count 1 t:\$_NOT_
select -module dffe_01 -assert-count 0 t:\$_NOT_

#------------------------------------------------------------------------------

# Same as first case, but on fine-grained cells

design -load before

techmap

clockgate -pos pdk_icg ce:clkin:clkout -tie_lo scanen

# falling edge clock flops don't get matched on -pos
select -module dffe_00 -assert-count 0 t:\\pdk_icg
select -module dffe_01 -assert-count 0 t:\\pdk_icg
# falling edge clock flops do get matched on -pos
select -module dffe_10 -assert-count 1 t:\\pdk_icg
select -module dffe_11 -assert-count 1 t:\\pdk_icg
# if necessary, EN is inverted, since the given ICG
# is assumed to have an active-high EN
select -module dffe_10 -assert-count 1 t:\$_NOT_
select -module dffe_11 -assert-count 0 t:\$_NOT_

# Extra credit: multi-bit FFs work fine as well
select -module dffe_wide_11 -assert-count 1 t:\\pdk_icg

#------------------------------------------------------------------------------

design -load before
clockgate -min_net_size 2 -neg pdk_icg ce:clkin:clkout -tie_lo scanen

# No FF set sharing a (clock, clock enable) pair is large enough
select -module dffe_00 -assert-count 0 t:\\pdk_icg
select -module dffe_01 -assert-count 0 t:\\pdk_icg
select -module dffe_10 -assert-count 0 t:\\pdk_icg
select -module dffe_11 -assert-count 0 t:\\pdk_icg

# TODO test -tie_lo