Add Range128 preprocessed column (#240)

prover/src/machine2/column.rs

@@ -186,6 +186,9 @@ pub enum PreprocessedColumn {
     /// Timestamp for the third register access
     #[size = 4]
     Reg3TsCur,
+    /// Contains numbers from 0 to 127, and 0 afterwards.
+    #[size = 1]
+    Range128,
     /// Contains numbers from 0 to 255, and 0 afterwards.
     #[size = 1]
     Range256,

prover/src/machine2/trace/mod.rs

@@ -135,6 +135,7 @@ impl Traces {
         ret.fill_is_first32();
         ret.fill_timestamps();
         ret.fill_range256();
+        ret.fill_range128();
         ret.fill_range32();
         ret.fill_bitwise();
         ret
@@ -361,6 +362,11 @@ impl Traces {
             self.cols[PreprocessedColumn::Range32.offset()][row_idx] = BaseField::from(row_idx);
         }
     }
+    fn fill_range128(&mut self) {
+        for row_idx in 0..128 {
+            self.cols[PreprocessedColumn::Range128.offset()][row_idx] = BaseField::from(row_idx);
+        }
+    }
     fn fill_timestamps(&mut self) {
         // Make sure the last reg3_ts_cur computation doesn't overflow
         debug_assert!(1 << self.log_size < (u32::MAX - 3) / 3);