feat: move is_commutative function to utils and update local CSE implementation

Author: metrics

crates/herkos-core/src/optimizer/local_cse.rs

@@ -8,7 +8,7 @@
 use crate::ir::{BinOp, IrFunction, IrInstr, IrValue, UnOp, VarId};
 use std::collections::HashMap;
 
-use super::utils::prune_dead_locals;
+use super::utils::{is_commutative, prune_dead_locals};
 
 // ── Value key ────────────────────────────────────────────────────────────────
 
@@ -45,37 +45,6 @@ impl From<IrValue> for ConstKey {
     }
 }
 
-// ── Commutative op detection ─────────────────────────────────────────────────
-
-/// Returns true for operations where `op(a, b) == op(b, a)`.
-fn is_commutative(op: &BinOp) -> bool {
-    matches!(
-        op,
-        BinOp::I32Add
-            | BinOp::I32Mul
-            | BinOp::I32And
-            | BinOp::I32Or
-            | BinOp::I32Xor
-            | BinOp::I32Eq
-            | BinOp::I32Ne
-            | BinOp::I64Add
-            | BinOp::I64Mul
-            | BinOp::I64And
-            | BinOp::I64Or
-            | BinOp::I64Xor
-            | BinOp::I64Eq
-            | BinOp::I64Ne
-            | BinOp::F32Add
-            | BinOp::F32Mul
-            | BinOp::F32Eq
-            | BinOp::F32Ne
-            | BinOp::F64Add
-            | BinOp::F64Mul
-            | BinOp::F64Eq
-            | BinOp::F64Ne
-    )
-}
-
 /// Build a `ValueKey` for a `BinOp`, normalizing operand order for commutative ops.
 fn binop_key(op: BinOp, lhs: VarId, rhs: VarId) -> ValueKey {
     let (lhs, rhs) = if is_commutative(&op) && lhs.0 > rhs.0 {
@@ -97,8 +66,11 @@ pub fn eliminate(func: &mut IrFunction) {
         let mut value_map: HashMap<ValueKey, VarId> = HashMap::new();
 
         for instr in &mut block.instructions {
-            // In strict SSA form each variable is defined exactly once, so there
-            // is no need to invalidate cached CSE entries on redefinition.
+            // This pass runs on lowered (post-phi) IR. While the function is no
+            // longer globally in SSA form, within any single block each BinOp,
+            // UnOp, and Const dest is still defined at most once: phi lowering
+            // only inserts Assigns into predecessor blocks, never into the block
+            // being processed. So value_map entries are never stale.
             match instr {
                 IrInstr::Const { dest, value } => {
                     let key = ValueKey::Const(ConstKey::from(*value));

crates/herkos-core/src/optimizer/utils.rs

@@ -466,6 +466,37 @@ pub fn is_side_effect_free(instr: &IrInstr) -> bool {
     }
 }
 
+// ── Commutative op detection ─────────────────────────────────────────────────
+
+/// Returns true for operations where `op(a, b) == op(b, a)`.
+pub fn is_commutative(op: &BinOp) -> bool {
+    matches!(
+        op,
+        BinOp::I32Add
+            | BinOp::I32Mul
+            | BinOp::I32And
+            | BinOp::I32Or
+            | BinOp::I32Xor
+            | BinOp::I32Eq
+            | BinOp::I32Ne
+            | BinOp::I64Add
+            | BinOp::I64Mul
+            | BinOp::I64And
+            | BinOp::I64Or
+            | BinOp::I64Xor
+            | BinOp::I64Eq
+            | BinOp::I64Ne
+            | BinOp::F32Add
+            | BinOp::F32Mul
+            | BinOp::F32Eq
+            | BinOp::F32Ne
+            | BinOp::F64Add
+            | BinOp::F64Mul
+            | BinOp::F64Eq
+            | BinOp::F64Ne
+    )
+}
+
 // ── Rewrite terminator block targets ─────────────────────────────────────────
 
 /// Rewrite all block-ID references in a terminator from `old` to `new`.

scripts/compare_metrics.py

@@ -238,14 +238,16 @@ def display_html(groups: Dict[str, List[Dict]], output_path: str = "metrics_repo
 
         timestamps = [parse_timestamp(e["timestamp"]).isoformat() for e in entries]
         values = [e["value"] for e in entries]
+        indices = list(range(len(entries)))
 
         fig.add_trace(
             go.Scatter(
-                x=timestamps,
+                x=indices,
                 y=values,
                 mode="lines+markers",
                 name=name,
-                hovertemplate=f"<b>{name}</b><br>Timestamp: %{{x}}<br>Value: %{{y:.2f}}<extra></extra>",
+                customdata=timestamps,
+                hovertemplate=f"<b>{name}</b><br>Timestamp: %{{customdata}}<br>Value: %{{y:.2f}}<extra></extra>",
             ),
             row=row,
             col=col,