opt_clean: Better memory handling.

Previously, `$memwr` and `$meminit` cells were always preserved (along
with the memory itself).  With this change, they are instead part of the
main cell mark-and-sweep pass: a memory (and its `$meminit` and `$memwr`
cells) is only preserved iff any associated `$memrd` cell needs to be
preserved.

1 files changed, 49 insertions, 0 deletions

diff --git a/tests/opt/opt_clean_mem.ys b/tests/opt/opt_clean_mem.ys
new file mode 100644
index 000000000..b35b15871
--- /dev/null
+++ b/tests/opt/opt_clean_mem.ys
@@ -0,0 +1,49 @@
+read_verilog <<EOT
+module top(...);
+
+input [7:0] wa;
+input [7:0] ra1;
+input [7:0] ra2;
+input [7:0] wd;
+input clk;
+wire [7:0] rd1;
+wire [7:0] rd2;
+
+reg [7:0] mem[0:7];
+
+always @(posedge clk)
+	mem[wa] <= wd;
+assign rd1 = mem[ra1];
+assign rd2 = mem[ra2];
+
+initial mem[8'h12] = 8'h34;
+
+endmodule
+EOT
+
+proc
+memory_dff
+
+select -assert-count 2 t:$memrd
+select -assert-count 1 t:$memwr
+select -assert-count 1 t:$meminit
+design -save orig
+
+opt_clean
+select -assert-none t:$memrd
+select -assert-none t:$memwr
+select -assert-none t:$meminit
+
+design -load orig
+expose top/rd1
+opt_clean
+select -assert-count 1 t:$memrd
+select -assert-count 1 t:$memwr
+select -assert-count 1 t:$meminit
+
+design -load orig
+expose top/rd1 top/rd2
+opt_clean
+select -assert-count 2 t:$memrd
+select -assert-count 1 t:$memwr
+select -assert-count 1 t:$meminit