Modify shift to fixed 1, 4, 8, and 16 shifts only (#91)

* hw: add shift modifications

* hw: update alu pe

* test: add hv shift

rtl/encoder/hv_alu_pe.sv

@@ -11,7 +11,7 @@ module hv_alu_pe #(
   parameter int unsigned HVDimension   = 512,
   parameter int unsigned NumOps        = 4,
   parameter int unsigned NumOpsWidth   = $clog2(NumOps),
-  parameter int unsigned MaxShiftAmt   = 128,
+  parameter int unsigned MaxShiftAmt   = 4,
   parameter int unsigned ShiftWidth    = $clog2(MaxShiftAmt)
 )(
   // Inputs
@@ -26,11 +26,24 @@ module hv_alu_pe #(
 
   //---------------------------
   // Logic for shifting
+  //
+  // Shifting modes:
+  // 0: 1 shift
+  // 1: 4 shift
+  // 2: 8 shift
+  // 3: 16 shift
   //---------------------------
   logic [HVDimension-1:0] circular_shift_res;
 
+  // Doing selections through wire slicing
+  // rather than actual shifts to optimize synthesis
   always_comb begin
-    circular_shift_res = (A_i >> shift_amt_i) | (A_i << (HVDimension - shift_amt_i));
+    case (shift_amt_i)
+      default: circular_shift_res = {A_i[   0], A_i[ HVDimension-1:1]};
+            1: circular_shift_res = {A_i[ 3:0], A_i[ HVDimension-1:4]};
+            2: circular_shift_res = {A_i[ 7:0], A_i[ HVDimension-1:8]};
+            3: circular_shift_res = {A_i[15:0], A_i[HVDimension-1:16]};
+    endcase
   end
 
   //---------------------------

tests/util.py

@@ -196,7 +196,7 @@ def gen_randint(max_val):
 
 # For the ALU output
 def hv_alu_out(hv_a, hv_b, shift_amt, hv_dim, op):
-    mask_val = 2**hv_dim - 1
+    2**hv_dim - 1
 
     if op == 1:
         result = hv_a
@@ -205,10 +205,11 @@ def hv_alu_out(hv_a, hv_b, shift_amt, hv_dim, op):
     elif op == 3:
         # Workaround because github CI fails
         # At shifting more than 64 bits
-        if isinstance(hv_a, np.ndarray):
-            result = np.roll(hv_a, shift_amt)
-        else:
-            result = (hv_a >> shift_amt) | (hv_a << (hv_dim - shift_amt)) & mask_val
+        # if isinstance(hv_a, np.ndarray):
+        #     result = np.roll(hv_a, shift_amt)
+        # else:
+        #     result = (hv_a >> shift_amt) | (hv_a << (hv_dim - shift_amt)) & mask_val
+        result = shift_hv(hv_a, shift_amt, hv_dim)
     else:
         result = hv_a ^ hv_b
     return result
@@ -245,6 +246,22 @@ def hvlist2num(hv_list):
     return hv_num
 
 
+# Shift modes based on shift values
+def shift_hv(hv_a, shift_amt, hv_dim):
+    mask_val = 2**hv_dim - 1
+
+    if shift_amt == 0:
+        result = (hv_a >> 1) | (hv_a << (hv_dim - 1)) & mask_val
+    elif shift_amt == 1:
+        result = (hv_a >> 4) | (hv_a << (hv_dim - 4)) & mask_val
+    elif shift_amt == 2:
+        result = (hv_a >> 8) | (hv_a << (hv_dim - 8)) & mask_val
+    else:
+        result = (hv_a >> 16) | (hv_a << (hv_dim - 16)) & mask_val
+
+    return result
+
+
 """
     Set of functions for the encoding module
 """