parameter functions

Author: rachitnigam

primitives/param-funcs.fil

@@ -0,0 +1,14 @@
+/**
+ * Computes the number of bits needed to represent the constant [N].
+ *  Usage:
+ *  ```filament
+ *  BN := new BitsNeeded[N];
+ *  let Bits = BN::Out;     // Out represents number of bits for [N]
+ *  ```
+ */
+comp BitsNeeded[N]<'G:1>() -> () with {
+  some Out where Out == log2(N)+1, Out > 0;
+} {
+  let Bits = log2(N)+1; assume Bits > 0;
+  Out := Bits;
+}

primitives/reshape.fil

@@ -1,4 +1,5 @@
 import "primitives/core.fil";
+import "primitives/param-funcs.fil";
 
 // A highly parameterized serializer. The parameters are:
 // * W: The width of the inputs
@@ -201,7 +202,8 @@ comp CollectValid[W, N]<'G:1>(
   out[N]: ['G, 'G+1] W,
   block_valid: ['G, 'G+1] 1
 ) where W > 0 {
-  let Bits = log2(N)+1; assume Bits > 0;
+  BN := new BitsNeeded[N];
+  let Bits = BN::Out;
 
   // Increment the index if the value on the stream is valid
   idx := new Prev[Bits, 1]<'G>(reset.out);