hakorune/docs/development/current/main/phases/phase-133

Phase 133: loop(true) break-once Multiple Post-Loop Assignments

Status: ✅ Implemented & Verified Date: 2025-12-18 Scope: P0 (Minimal)

Overview

Phase 133-P0 extends Phase 132-P4's loop(true) break-once pattern to accept multiple post-loop assignments before the final return statement. This enables more complex post-loop computation while maintaining the PHI-free Normalized shadow architecture.

Pattern

x = 0              // pre-loop init
loop(true) {       // condition is Bool literal true
    x = 1          // body assignment
    break          // break at end
}
x = x + 2          // first post-loop assignment
x = x + 3          // second post-loop assignment (NEW in P133)
return x           // return updated value (1 + 2 + 3 = 6)

Implementation Changes

1. Pattern Detection (loop_true_break_once.rs)

Extended from Phase 132:

• Phase 132: post_nodes == [Assign, Return] (exactly 1 assign)
• Phase 133: post_nodes == [Assign+, Return] (1+ assigns)

// Phase 133-P0: Detect multi-assign + return pattern (generalize Phase 132-P4)
let has_post_computation = if post_nodes.is_empty() {
    false
} else if post_nodes.len() >= 2 {
    // Check if all nodes except the last are Assign statements
    let all_assigns = post_nodes[..post_nodes.len() - 1]
        .iter()
        .all(|n| matches!(n, StepNode::Stmt { kind: StepStmtKind::Assign { .. }, .. }));

    // Check if the last node is a Return statement
    let ends_with_return = matches!(
        post_nodes.last(),
        Some(StepNode::Stmt { kind: StepStmtKind::Return { .. }, .. })
    );

    all_assigns && ends_with_return
} else {
    false
};

2. Post-Loop Lowering (loop_true_break_once.rs)

Iterative Assignment Processing:

// Phase 133-P0: Lower multiple post-loop assignments
// Split post_nodes into assigns and return (last element is return)
let assign_nodes = &post_nodes[..post_nodes.len() - 1];
let return_node = post_nodes.last().unwrap();

// Lower all assignment statements
for node in assign_nodes {
    let StepNode::Stmt { kind: StepStmtKind::Assign { target, value_ast }, .. } = node else {
        return Ok(None);
    };
    if LegacyLowerer::lower_assign_stmt(
        target,
        value_ast,
        &mut post_k_func.body,
        &mut next_value_id,
        &mut env_post_k,
    )
    .is_err()
    {
        return Ok(None);
    }
}

3. SSOT Maintenance

ExitMeta Contract:

• Unchanged: ExitMeta still uses env_post_k's final values as SSOT
• Iterative Updates: Each assignment updates env_post_k map
• Final State: Last assignment's result becomes the exit value

JoinIR Structure (Unchanged from Phase 132)

5-Function Module:

1. main(env) → TailCall(loop_step, env)
2. loop_step(env) → TailCall(loop_body, env)
3. loop_body(env) → → TailCall(k_exit, env)
4. k_exit(env) → TailCall(post_k, env)
5. post_k(env) → * → Ret(env[x]) ← NEW: Multiple assigns

Contract:

• PHI-free: All state passing via env arguments + continuations
• DirectValue mode: ExitMeta uses post_k's final env values

Scope Limitations (Phase 130 Baseline)

Allowed Assignments:

• ✅ x = <int literal> (e.g., x = 0)
• ✅ x = y (variable copy)
• ✅ x = x + <int literal> (increment)

Not Allowed:

• ❌ x = call(...) (function calls)
• ❌ x = a + b (general binary ops)
• ❌ if, loop, print in post-loop

Test Coverage

Fixture

• apps/tests/phase133_loop_true_break_once_post_multi_add_min.hako
• Expected exit code: 6 (1 + 2 + 3)

Smoke Tests

1. VM: tools/smokes/v2/profiles/integration/apps/phase133_loop_true_break_once_post_multi_add_vm.sh
2. LLVM EXE: tools/smokes/v2/profiles/integration/apps/phase133_loop_true_break_once_post_multi_add_llvm_exe.sh

Regression Tests

• ✅ Phase 132 (exit code 3)
• ✅ Phase 131 (exit code 1)
• ✅ Phase 97 (numeric output 2, -1, 3)

Verification Results

# Unit tests
cargo test --lib
# Result: 1176 passed; 0 failed

# Phase 133 smokes
bash tools/smokes/v2/profiles/integration/apps/phase133_loop_true_break_once_post_multi_add_vm.sh
# Result: PASS (exit code 6)

bash tools/smokes/v2/profiles/integration/apps/phase133_loop_true_break_once_post_multi_add_llvm_exe.sh
# Result: PASS (exit code 6)

# Regression smokes
bash tools/smokes/v2/profiles/integration/apps/phase132_loop_true_break_once_post_add_llvm_exe.sh
# Result: PASS (exit code 3)

bash tools/smokes/v2/profiles/integration/apps/phase131_loop_true_break_once_llvm_exe.sh
# Result: PASS (exit code 1)

bash tools/smokes/v2/profiles/integration/apps/phase97_next_non_ws_llvm_exe.sh
# Result: PASS (numeric output)

Design Principles

1. Minimal Change

• Extends Phase 132's detection logic from len() == 2 to len() >= 2
• Replaces single assignment lowering with iterative loop
• Zero changes to JoinIR structure, ExitMeta, or merge logic

2. SSOT Preservation

• env_post_k remains the single source of truth for exit values
• Each assignment updates env_post_k map in order
• ExitMeta collection happens after all assignments

3. Reuse

• Uses LegacyLowerer::lower_assign_stmt for each assignment
• Leverages Phase 130's proven assignment handling
• No new lowering code required

4. Fail-Fast

• Contract violations trigger freeze_with_hint in strict mode
• Missing env fields → explicit error with hint
• Invalid assignment → fallback to legacy (Ok(None))

Dev Toggle

Required: NYASH_JOINIR_DEV=1 and HAKO_JOINIR_STRICT=1

This is a dev-only Normalized shadow feature. With toggle OFF, the pattern falls back to legacy lowering with zero impact on production code.

Files Modified

1. src/mir/control_tree/normalized_shadow/loop_true_break_once.rs (3 edits)

   • Extended pattern detection
   • Iterative assignment lowering
   • Updated debug logging

2. apps/tests/phase133_loop_true_break_once_post_multi_add_min.hako (new)

3. tools/smokes/v2/profiles/integration/apps/phase133_loop_true_break_once_post_multi_add_vm.sh (new)

4. tools/smokes/v2/profiles/integration/apps/phase133_loop_true_break_once_post_multi_add_llvm_exe.sh (new)

Acceptance Criteria

• ✅ cargo test --lib PASS (1176 tests)
• ✅ Phase 133 VM smoke: PASS (exit code 6)
• ✅ Phase 133 LLVM EXE smoke: PASS (exit code 6)
• ✅ Phase 132 regression: PASS (exit code 3)
• ✅ Phase 131 regression: PASS (exit code 1)
• ✅ Phase 97 regression: PASS (numeric output)
• ✅ Dev toggle OFF: Zero impact on production

Summary

Phase 133-P0 successfully generalizes Phase 132-P4's single post-loop assignment to support multiple post-loop assignments, enabling more complex post-loop computation patterns. The implementation maintains all architectural invariants (PHI-free, DirectValue mode, SSOT) while adding only ~30 lines of code.

Key Achievement: Transformed fixed-length pattern detection (len() == 2) to flexible pattern detection (len() >= 2) with zero impact on existing contracts.