338d1aecf1
Implement dual-mode architecture for Pattern 3 (Loop with If-Else PHI): - Add is_simple_if_sum_pattern() detection helper - Detects 1 CounterLike + 1-2 AccumulationLike carrier patterns - Unit tests for various carrier compositions - Add dual-mode dispatch in Pattern3 lowerer - ctx.is_if_sum_pattern() branches to AST-based vs legacy PoC - Legacy mode preserved for backward compatibility - Create loop_with_if_phi_if_sum.rs (~420 lines) - AST extraction: loop condition, if condition, updates - JoinIR generation: main, loop_step, k_exit structure - Helper functions: extract_loop_condition, extract_if_condition, etc. - Extend PatternPipelineContext for Pattern 3 - is_if_sum_pattern() detection using LoopUpdateSummary - extract_if_statement() helper for body analysis Note: E2E RC=2 not yet achieved due to pre-existing Pattern 3 pipeline issue (loop back branch targets wrong block). This affects both if-sum and legacy modes. Fix planned for Phase 214. 🤖 Generated with [Claude Code](https://claude.com/claude-code) Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>
99 lines
3.2 KiB
Markdown
99 lines
3.2 KiB
Markdown
# Phase 213: Pattern 3 If-Sum AST-based Lowerer
|
|
|
|
## Overview
|
|
|
|
Phase 213 implements an AST-based JoinIR lowerer for "simple if-sum" patterns in Pattern 3 (Loop with If-Else PHI).
|
|
|
|
## Design Decision: Approach B
|
|
|
|
**Dual-mode architecture**:
|
|
1. **if-sum mode**: AST-based lowering for simple patterns (e.g., `phase212_if_sum_min.hako`)
|
|
2. **legacy mode**: Hardcoded PoC lowering for existing tests (e.g., `loop_if_phi.hako`)
|
|
|
|
This approach:
|
|
- Minimizes risk by keeping legacy code path intact
|
|
- Only generalizes for detected if-sum patterns
|
|
- Enables incremental migration
|
|
|
|
## Implementation
|
|
|
|
### Files Modified/Created
|
|
|
|
1. **`loop_update_summary.rs`**
|
|
- Added `is_simple_if_sum_pattern()` method
|
|
- Detects: 1 CounterLike + 1-2 AccumulationLike carriers
|
|
|
|
2. **`pattern_pipeline.rs`**
|
|
- Added `is_if_sum_pattern()` to PatternPipelineContext
|
|
- Added `extract_if_statement()` helper
|
|
|
|
3. **`pattern3_with_if_phi.rs`**
|
|
- Dual-mode dispatch: `ctx.is_if_sum_pattern()` → branch
|
|
- `lower_pattern3_if_sum()`: calls AST-based lowerer
|
|
- `lower_pattern3_legacy()`: existing hardcoded logic
|
|
|
|
4. **`loop_with_if_phi_if_sum.rs`** (NEW)
|
|
- AST-based if-sum lowerer (~420 lines)
|
|
- Extracts from AST:
|
|
- Loop condition (`i < len`)
|
|
- If condition (`i > 0`)
|
|
- Then update (`sum = sum + 1`)
|
|
- Counter update (`i = i + 1`)
|
|
- Generates JoinIR with dynamic values
|
|
|
|
### Pattern Detection
|
|
|
|
```rust
|
|
pub fn is_simple_if_sum_pattern(&self) -> bool {
|
|
if self.counter_count() != 1 { return false; }
|
|
if self.accumulation_count() < 1 { return false; }
|
|
if self.accumulation_count() > 2 { return false; }
|
|
true
|
|
}
|
|
```
|
|
|
|
### AST Extraction
|
|
|
|
The lowerer extracts pattern components from AST:
|
|
- `extract_loop_condition()`: `i < 3` → (var="i", op=Lt, limit=3)
|
|
- `extract_if_condition()`: `i > 0` → (var="i", op=Gt, value=0)
|
|
- `extract_then_update()`: `sum = sum + 1` → (var="sum", addend=1)
|
|
- `extract_counter_update()`: `i = i + 1` → (var="i", step=1)
|
|
|
|
## Testing Results
|
|
|
|
### AST Extraction: Working ✅
|
|
```
|
|
[joinir/pattern3/if-sum] Loop condition: i Lt 3
|
|
[joinir/pattern3/if-sum] If condition: i Gt 0
|
|
[joinir/pattern3/if-sum] Then update: sum += 1
|
|
[joinir/pattern3/if-sum] Counter update: i += 1
|
|
```
|
|
|
|
### Known Issue: Pattern 3 Pipeline
|
|
|
|
**Both if-sum mode and legacy mode return RC=0 instead of expected values.**
|
|
|
|
This is a pre-existing issue in the JoinIR → MIR conversion pipeline (Phase 33-21/177):
|
|
- Loop back branch targets `bb5` instead of loop header `bb4`
|
|
- PHI nodes not properly updated on loop back
|
|
|
|
**This issue is NOT specific to Phase 213** - the legacy `loop_if_phi.hako` has the same problem.
|
|
|
|
## Future Work
|
|
|
|
1. **Phase 214+**: Fix Pattern 3 JoinIR → MIR pipeline
|
|
- Investigate loop back branch target
|
|
- Ensure PHI updates are correctly wired
|
|
|
|
2. **Phase 213-B** (optional): Support variable limits
|
|
- Currently only integer literals supported
|
|
- `i < len` where `len` is a variable → Phase 214+
|
|
|
|
## File Locations
|
|
|
|
- Lowerer: `src/mir/join_ir/lowering/loop_with_if_phi_if_sum.rs`
|
|
- Dispatcher: `src/mir/builder/control_flow/joinir/patterns/pattern3_with_if_phi.rs`
|
|
- Pattern detection: `src/mir/join_ir/lowering/loop_update_summary.rs`
|
|
- Pipeline context: `src/mir/builder/control_flow/joinir/patterns/pattern_pipeline.rs`
|