Merge pull request #210 from Tcode-Motion/optimize-cfg-lookup-16169091484459046166

⚡ O(1) CFG successor lookup in IR verifier

Author: github-actions[bot]

.jules/bolt.md

@@ -41,3 +41,6 @@
 ## 2026-09-24 - Zero-allocation hex decoding
 **Learning:** Using `hex::decode` from the `hex` crate provides a significant performance boost over manually iterating through strings and calling `u8::from_str_radix`, even though `hex::decode` allocates a new `Vec<u8>`. It avoids the heavy intermediate allocations and processing overhead of manual string slice iterations.
 **Action:** Always prefer `hex::decode` and `hex::encode` when working with hexadecimal encoding/decoding instead of manual iterative string parsing to significantly boost performance.
+## 2024-05-18 - Optimized CFG Successor Lookup
+**Learning:** During control flow graph validation in `compiler/optimizer/src/verifier.rs`, using `func.blocks.iter().find(|b| b.id == succ)` for every successor of every block created an O(V * E) time complexity bottleneck. By pre-computing a `HashMap` of `BlockId` to `&BasicBlock` in a single pass, the verification complexity was reduced to O(V + E).
+**Action:** When validating graph structures or resolving many cross-references within a known collection, construct a lookup map in advance instead of performing repeated O(N) linear scans.

compiler/optimizer/src/verifier.rs

@@ -1,4 +1,4 @@
-use std::collections::HashSet;
+use std::collections::{HashMap, HashSet};
 use techscript_ir::block::BasicBlock;
 use techscript_ir::function::Function;
 use techscript_ir::module::Module;
@@ -27,7 +27,14 @@ impl IRVerifier {
     }
 
     fn verify_function(&self, func: &Function) -> Result<(), String> {
-        let block_ids: HashSet<_> = func.blocks.iter().map(|b| b.id).collect();
+        let mut block_ids: HashSet<_> = HashSet::with_capacity(func.blocks.len());
+        // ⚡ Bolt Performance Optimization:
+        // Use HashMap for O(1) block lookups instead of O(N) linear scans during CFG verification.
+        let mut block_map = HashMap::with_capacity(func.blocks.len());
+        for b in &func.blocks {
+            block_ids.insert(b.id);
+            block_map.insert(b.id, b);
+        }
 
         for block in &func.blocks {
             self.verify_block(block, &block_ids)?;
@@ -36,8 +43,7 @@ impl IRVerifier {
         // Verify CFG link mapping consistency
         for block in &func.blocks {
             for &succ in &block.successors {
-                let succ_block = func.blocks.iter().find(|b| b.id == succ);
-                if let Some(sb) = succ_block {
+                if let Some(&sb) = block_map.get(&succ) {
                     if !sb.predecessors.contains(&block.id) {
                         return Err(format!(
                             "CFG inconsistency: Block '{}' lists '{}' as successor, but '{}' does not list '{}' as predecessor",