designs/asap7/mac: added a MAC as a test-case for retiming

Signed-off-by: Øyvind Harboe <[email protected]>

Author: oharboe

flow/designs/asap7/mac/config.mk

@@ -0,0 +1,6 @@
+export DESIGN_NAME = mac
+export VERILOG_FILES = designs/src/mac/mac.v
+export SDC_FILE = designs/asap7/mac/constraints.sdc
+export PLATFORM = asap7
+export PLACE_DENSITY= 0.30
+export CORE_UTILIZATION = 0.50

flow/designs/asap7/mac/constraints.sdc

@@ -0,0 +1,5 @@
+set clk_name clock
+set clk_port_name clock
+set clk_period 250
+
+source $env(PLATFORM_DIR)/constraints.sdc

flow/designs/src/mac/mac.v

@@ -0,0 +1,43 @@
+module mac (
+    input  logic         clock,
+    input  logic [15:0]  a,
+    input  logic [15:0]  b,
+    input  logic         valid_in,
+    output logic [31:0]  acc_out,
+    output logic         valid_out
+);
+    // Pipeline registers for a, b, and valid
+    logic [15:0] a_pipe [0:3];
+    logic [15:0] b_pipe [0:3];
+    logic        valid_pipe [0:3];
+    logic [31:0] mul_result;
+    logic [31:0] acc;
+
+    always_ff @(posedge clock) begin
+        // Stage 0: input register
+        a_pipe[0] <= a;
+        b_pipe[0] <= b;
+        valid_pipe[0] <= valid_in;
+
+        // Stages 1-3: pipeline shift
+        a_pipe[1] <= a_pipe[0];
+        b_pipe[1] <= b_pipe[0];
+        valid_pipe[1] <= valid_pipe[0];
+
+        a_pipe[2] <= a_pipe[1];
+        b_pipe[2] <= b_pipe[1];
+        valid_pipe[2] <= valid_pipe[1];
+
+        a_pipe[3] <= a_pipe[2];
+        b_pipe[3] <= b_pipe[2];
+        valid_pipe[3] <= valid_pipe[2];
+
+        // Stage 4: multiply and accumulate
+        mul_result <= a_pipe[3] * b_pipe[3];
+        if (valid_pipe[3])
+            acc <= acc + mul_result;
+    end
+
+    assign acc_out = acc;
+    assign valid_out = valid_pipe[3];
+endmodule