Files
hakorune/src/tests
nyash-codex 5b7818f5c9 feat(joinir): Phase 33-7 IfMerge lowering for multiple-variable PHI
Implements IfMerge instruction lowering to support multiple variables
merging from if/else branches (Phase 33-7: return pattern only).

## Changes

- Add src/mir/join_ir/lowering/if_merge.rs (232 lines)
  - IfMergeLowerer with pattern matching for common variables
  - extract_written_vars() / find_written_value() helpers
  - Phase 33-7 constraint: return pattern only (k_next=None)

- Update src/mir/join_ir/lowering/mod.rs
  - Unified entry point: try_lower_if_to_joinir()
  - Priority: IfMerge → Select → if_phi fallback
  - Add IfMergeTest.* to whitelist

- Add unit tests in src/tests/mir_joinir_if_select.rs
  - test_if_merge_simple_pattern (2 variables)
  - test_if_merge_multiple_pattern (3 variables)
  - All 7/7 tests PASS 

- Add reference test cases
  - apps/tests/joinir_if_merge_simple.hako (2-var pattern)
  - apps/tests/joinir_if_merge_multiple.hako (3-var pattern)

## Test Results

 Simple pattern (2 vars): merges=2, k_next=None
 Multiple pattern (3 vars): merges=3, k_next=None
 test result: ok. 7 passed; 0 failed

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude <noreply@anthropic.com>
2025-11-27 08:18:09 +09:00
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