W22 cluster: fix 3 cond_branch Edge::set_to bypass sites in builder_emit_c.c

SonicField · SonicField · commit 678e9905a871 · 2026-04-23T12:29:49.000-07:00
GDB investigation 2026-04-23 19:11Z + librarian 19:13:55Z pointed at feedback_edge_management.md: terminator factories MUST use the C++ bridge (Edge::set_to manages BasicBlock::in_edges_) — direct .to writes leave target blocks unaware of their predecessors and corrupt CFG-DFS. Three production-path callers in builder_emit_c.c were using the BAD pure-C cond_branch factory (hir_c_create_cond_branch) instead of the required _cpp variant: Line 4207 — hir_builder_emit_send_c (SEND bytecode) Used in await/yield-from execution path. The done_block after SEND's cond branch was orphaned in CFG, causing hir_remove_unreachable_blocks_c to either crash on NULL terminator (gen_chain test) or to walk into garbage successors via stale .to pointers (await_caller test). Line 4458 — emitMatchClass (attrs_tuple type-check branch) Surfaced through earlier test runs. Line 4522 — emitMatchMappingSequence (and_result branch) Surfaced through earlier test runs. The non-_cpp factory has an explicit "DO NOT USE for production" warning at hir_instr_c.h:1170-1172 + 1184-1185. These three sites slipped past audit during W27 emit-method conversion. Verification at HEAD post-fix: /tmp/test_await_autocompile.py: PASS — await_caller is_jit_compiled= True, coro_returns_value is_jit_compiled=True (was: SIGSEGV at iter 1000 in JIT compilation of asyncio internals) test_phoenix_jit_autocompile.test_gen_chain: PASS (was: SIGSEGV in hir_remove_unreachable_blocks_c NULL terminator) /tmp/repro_min3.py yield-from: PASS (no regression) Full test_phoenix_jit_{comparisons,controlflow,autocompile}: 368 tests PASS (no regressions; was 244 PASS pre-fix, +124 from autocompile suite passing test_gen_chain) W22 surface + 3 of 4 follow-on bugs (yield-from, controlflow, comparisons, await deopt v27, await runtime, gen_chain) all FIXED via 3-commit cluster (66850a4 → f47bcc9 → 11db74f88c → THIS commit). Refs: feedback_edge_management.md (Edge::set_to bridge requirement); prior identical incident at 06e2ecb/7d0aff1e42 fixed by 61c319c per librarian 19:13:55Z.
diff --git a/Python/jit/hir/builder_emit_c.c b/Python/jit/hir/builder_emit_c.c
@@ -4204,7 +4204,13 @@ void hir_builder_emit_send_c(
 
     void *done_block = hir_builder_get_block_at_off(builder, jump_target_off);
     void *continue_block = hir_builder_get_block_at_off(builder, next_instr_off);
-    phx_tc_emit(tc, hir_c_create_cond_branch(is_done, done_block, continue_block));
+    /* hir_c_create_cond_branch_cpp: uses Edge::set_to which manages the
+     * target BasicBlock's in_edges_ set. The pure-C hir_c_create_cond_branch
+     * bypasses Edge::set_to (writes edge.to directly), leaving target
+     * blocks unaware of their predecessor — which corrupts CFG-DFS in
+     * hir_remove_unreachable_blocks_c (W22 cluster gen_chain/await
+     * crash, gdb 19:11Z + librarian 19:13:55Z + feedback_edge_management.md). */
+    phx_tc_emit(tc, hir_c_create_cond_branch_cpp(is_done, done_block, continue_block));
 }
 
 /* W27c #5: emitSequenceSet (SEQUENCE_SET, Static Python). Mirrors C++
@@ -4455,7 +4461,8 @@ void hir_builder_emit_match_class_c(
     void *false_block = hir_cfg_alloc_block(func);
     void *done = hir_cfg_alloc_block(func);
 
-    phx_tc_emit(tc, hir_c_create_cond_branch(attrs_tuple, true_block, false_block));
+    /* _cpp variant required: Edge::set_to manages BasicBlock in_edges_. */
+    phx_tc_emit(tc, hir_c_create_cond_branch_cpp(attrs_tuple, true_block, false_block));
 
     tc->block = true_block;
     phx_tc_emit(tc, hir_c_create_refine_type_reg(
@@ -4519,7 +4526,8 @@ void hir_builder_emit_match_mapping_sequence_c(
 
     void *true_block = hir_cfg_alloc_block(func);
     void *false_block = hir_cfg_alloc_block(func);
-    phx_tc_emit(tc, hir_c_create_cond_branch(and_result, true_block, false_block));
+    /* _cpp variant required: Edge::set_to manages BasicBlock in_edges_. */
+    phx_tc_emit(tc, hir_c_create_cond_branch_cpp(and_result, true_block, false_block));
 
     void *result = hir_builder_temps_alloc_stack(builder);
     void *done = hir_cfg_alloc_block(func);
