d4f90976da
Unify condition lowering logic across Pattern 2/4 with trait-based API. New infrastructure: - condition_lowering_box.rs: ConditionLoweringBox trait + ConditionContext (293 lines) - ExprLowerer implements ConditionLoweringBox trait (+51 lines) Pattern migrations: - Pattern 2 (loop_with_break_minimal.rs): Use trait API - Pattern 4 (loop_with_continue_minimal.rs): Use trait API Benefits: - Unified condition lowering interface - Extensible for future lowering strategies - Clean API boundary between patterns and lowering logic - Zero code duplication Test results: 911/911 PASS (+2 new tests) 🤖 Generated with [Claude Code](https://claude.com/claude-code) Co-Authored-By: Claude Sonnet 4.5 <noreply@anthropic.com>
101 lines
3.3 KiB
Markdown
101 lines
3.3 KiB
Markdown
# Phase 213: Pattern 3 If-Sum AST-based Lowerer
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## Overview
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Phase 213 implements an AST-based JoinIR lowerer for "simple if-sum" patterns in Pattern 3 (Loop with If-Else PHI).
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## Design Decision: Approach B
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**Dual-mode architecture**:
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1. **if-sum mode**: AST-based lowering for simple patterns (e.g., `phase212_if_sum_min.hako`)
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2. **legacy mode**: Hardcoded PoC lowering for existing tests (e.g., `loop_if_phi.hako`)
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This approach:
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- Minimizes risk by keeping legacy code path intact
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- Only generalizes for detected if-sum patterns
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- Enables incremental migration
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## Implementation
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### Files Modified/Created
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1. **`loop_update_summary.rs`**
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- Added `is_simple_if_sum_pattern()` method
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- Detects: 1 CounterLike + 1-2 AccumulationLike carriers
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2. **`pattern_pipeline.rs`**
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- Added `is_if_sum_pattern()` to PatternPipelineContext
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- Added `extract_if_statement()` helper
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3. **`pattern3_with_if_phi.rs`**
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- Dual-mode dispatch: `ctx.is_if_sum_pattern()` → branch
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- `lower_pattern3_if_sum()`: calls AST-based lowerer
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- `lower_pattern3_legacy()`: existing hardcoded logic
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4. **`loop_with_if_phi_if_sum.rs`** (NEW)
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- AST-based if-sum lowerer (~420 lines)
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- Extracts from AST:
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- Loop condition (`i < len`)
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- If condition (`i > 0`)
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- Then update (`sum = sum + 1`)
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- Counter update (`i = i + 1`)
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- Generates JoinIR with dynamic values
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### Pattern Detection
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```rust
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pub fn is_simple_if_sum_pattern(&self) -> bool {
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if self.counter_count() != 1 { return false; }
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if self.accumulation_count() < 1 { return false; }
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if self.accumulation_count() > 2 { return false; }
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true
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}
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```
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### AST Extraction
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The lowerer extracts pattern components from AST:
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- `extract_loop_condition()`: `i < 3` → (var="i", op=Lt, limit=3)
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- `extract_if_condition()`: `i > 0` → (var="i", op=Gt, value=0)
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- `extract_then_update()`: `sum = sum + 1` → (var="sum", addend=1)
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- `extract_counter_update()`: `i = i + 1` → (var="i", step=1)
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## Testing Results
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### AST Extraction: Working ✅
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```
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[joinir/pattern3/if-sum] Loop condition: i Lt 3
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[joinir/pattern3/if-sum] If condition: i Gt 0
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[joinir/pattern3/if-sum] Then update: sum += 1
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[joinir/pattern3/if-sum] Counter update: i += 1
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```
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### Known Issue: Pattern 3 Pipeline
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**Both if-sum mode and legacy mode return RC=0 instead of expected values.**
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This is a pre-existing issue in the JoinIR → MIR conversion pipeline (Phase 33-21/177):
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- Loop back branch targets `bb5` instead of loop header `bb4`
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- PHI nodes not properly updated on loop back
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**This issue is NOT specific to Phase 213** - the legacy `loop_if_phi.hako` has the same problem.
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## Future Work
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1. **Phase 214+**: Fix Pattern 3 JoinIR → MIR pipeline
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- Investigate loop back branch target
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- Ensure PHI updates are correctly wired
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2. **Phase 213-B** (optional): Support variable limits
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- Currently only integer literals supported
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- `i < len` where `len` is a variable → Phase 214+
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## File Locations
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- Lowerer: `src/mir/join_ir/lowering/loop_with_if_phi_if_sum.rs`
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- Dispatcher: `src/mir/builder/control_flow/joinir/patterns/pattern3_with_if_phi.rs`
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- Pattern detection: `src/mir/join_ir/lowering/loop_update_summary.rs`
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- Pipeline context: `src/mir/builder/control_flow/joinir/patterns/pattern_pipeline.rs`
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Status: Active
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Scope: If-sum 実装（JoinIR v2）
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