811dfebf98
Remove legacy hardcoded 'sum' carrier validation that was blocking array_filter patterns with different accumulator names (e.g., 'out'). Before: Pattern3 required carrier named 'sum' to exist After: Pattern3 uses carrier_info generically (any carrier name works) Test results: - phase49_joinir_array_filter_smoke: PASS ✅ - phase49_joinir_array_filter_fallback: PASS ✅ - phase49_joinir_array_filter_ab_comparison: PASS ✅ - Full suite: 909/909 PASS, 0 FAIL Also: Archive old roadmap documentation (67k lines moved to docs/archive/) 🤖 Generated with [Claude Code](https://claude.com/claude-code) Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>
109 lines
2.6 KiB
Markdown
109 lines
2.6 KiB
Markdown
# Phase 195: Pattern 4 (Loop with Continue) Implementation Plan
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Status: Historical
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**Status**: Deferred (not yet implemented)
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## Overview
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Pattern 4 handles loops with `continue` statements that skip to the next iteration. This is the most complex loop pattern due to additional control flow requirements.
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## Why Deferred?
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1. **Continue semantics require additional PHI and control flow analysis**
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- Continue creates an additional edge to the loop header
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- Requires phi nodes for both continue and normal paths
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- More complex than break (which exits the loop)
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2. **Pattern 3 covers most practical cases**
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- Pattern 1: Simple while loops
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- Pattern 2: Loops with break
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- Pattern 3: Loops with if + PHI (most common complex pattern)
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- Pattern 4: Loops with continue (less common in practice)
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3. **Lower priority than break/if patterns**
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- Break patterns (Pattern 2) are more common
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- If + PHI patterns (Pattern 3) handle complex control flow
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- Continue can often be refactored using if statements
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## Example Use Case
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```nyash
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local i = 0
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local sum = 0
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loop(i < 10) {
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i = i + 1
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if (i % 2 == 0) {
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continue // Skip even numbers
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}
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sum = sum + i
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}
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// sum = 25 (1+3+5+7+9)
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```
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## Implementation Requirements
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When implemented, Pattern 4 lowering will need to:
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1. **Detect continue statements** in the loop body
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2. **Generate PHI nodes** for continue target (loop header)
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3. **Handle carrier variables** (i, sum) across continue boundaries
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4. **Generate exit PHI nodes** for final values after loop
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## Control Flow Diagram
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```
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header
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v
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body
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/----+----\
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/ \
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v v
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continue normal
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\-----+-------/
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v
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latch
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/---+---\
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/ \
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v v
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loop exit
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```
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## Workaround
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Until Pattern 4 is implemented, use Pattern 3 (if + PHI) instead:
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```nyash
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local i = 0
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local sum = 0
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loop(i < 10) {
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i = i + 1
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if (not (i % 2 == 0)) { // Invert condition
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sum = sum + i
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}
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}
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```
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## Migration Path
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1. **Pattern 1**: Simple while loops (no break/continue)
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2. **Pattern 2**: Loops with break
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3. **Pattern 3**: Loops with if + PHI
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4. **Pattern 4**: (FUTURE) Loops with continue statements
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## Related Files
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- `src/mir/builder/control_flow/joinir/patterns/pattern4_with_continue.rs` - Stub implementation
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- `src/mir/join_ir/lowering/loop_with_continue_minimal.rs` - Lowering logic (TODO)
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## Timeline
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- Phase 195+: Implementation planned but deferred
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- Priority: Lower than Pattern 1-3
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- Complexity: High (additional control flow edges)
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