Add comments per Kokubun's suggestion

Author: jacob-shops

zjit/src/hir.rs

@@ -6184,7 +6184,8 @@ impl Function {
         let max_params = blocks.iter().copied().map(|id| self.blocks[id].params.len()).max().unwrap_or(0);
         let mut trivial_indices: Vec<usize> = Vec::with_capacity(max_params);
 
-        // Prepare the initial param_values
+        // Prepare the initial param_values. As trivial block params are discovered and elided during analysis,
+        // the number of params in each row will decrease.
         for (row, block) in param_values.iter_mut().zip(&self.blocks) {
             row.resize(block.params.len(), ParamValue::None);
         }
@@ -6194,6 +6195,11 @@ impl Function {
         while changed {
             changed = false;
 
+            // When trivial params are elided, the number of params per block can shrink.
+            // When we reset each analysis loop, we do two things:
+            // 1. Reset analysis state to None (bottom of the lattice)
+            // 2. Shrink the number of params per row to match the params per block.
+            //    This resizing occurs when former iterations have found and removed trivial params.
             for (row, block) in param_values.iter_mut().zip(&self.blocks) {
                 row.truncate(block.params.len());
                 row.as_mut_slice().fill(ParamValue::None);