Self-host M4: bootstrap_loop gen-2 native emit — parseAndCompile returned null

Milestone

M4 — gen-2 native emit on bootstrap_loop_smoke (parent #1498 / #1492)

Problem

With native M4 flags, gen-1 link succeeds but gen-2 compile uses Zend fallback:

bootstrap-loop-gen1-link: gen-2 emit_path=zend (bin/compile.php) — native emit failed at phase=parseAndCompile
bootstrap-loop-gen1-link: OK emit_path=zend partial ... (gen-1 native compile blocked)

Same emit-TU spine failure as M3 runtime probe; blocks honest M4 loop before gen-1 can execute compiled bin/compile.php.

Scope

Area	Path
Loop scaffold	`test/selfhost/bootstrap_loop_smoke/`
Gen-1 link	`script/bootstrap-loop-gen1-link.sh`
Gen-2 emit entry	loop smoke emit helper + `lib/JIT/BootstrapCompileSmokeM3Emit.php`
JIT	`lib/JIT.php` emit-TU path

Repro

./script/docker-exec.sh -- bash -lc '
  source script/php-env.sh
  BOOTSTRAP_M4_LINK_COMPILE_DRIVER=1 \
  BOOTSTRAP_M4_RUNTIME_COMPILE=1 \
  ./script/bootstrap-loop-gen1-link.sh
'
# gen-2: parseAndCompile returned null → emit_path=zend partial

Strict (refuses Zend):

BOOTSTRAP_M4_GEN2_STRICT=1 BOOTSTRAP_M4_LINK_COMPILE_DRIVER=1 \
  BOOTSTRAP_M4_RUNTIME_COMPILE=1 \
  ./script/bootstrap-loop-gen1-link.sh

Done when

BOOTSTRAP_M4_LINK_COMPILE_DRIVER=1 ./script/bootstrap-loop-gen1-link.sh reports native gen-2 emit (not emit_path=zend partial)
make bootstrap-loop-probe exits 0 without --dry-run (after M3 strict green)
Paced by M3 emit-TU fixes (Self-host M3: runtime_m3_emit execute — parseAndCompile returned null (smallest emit TU) #2559 runtime TU, Self-host M3: PHPTypes/CFG static init in emit-TU LLVM global ctor (link segfault) #2540 HelloWorld execute)

Labels

self-host, bootstrap, IMPORTANT

Epic #1492 · #2551 (gen-1 execute) · #2075 · #2541

Superseded scope note (2026-05-26): With BOOTSTRAP_M4_RUNTIME_COMPILE=1, gen-2 parseAndCompile is no longer null — emit_path=native and compiler smoke stdout. Keep open only for default-off dry-run path; primary work moved to #2599 (runtime init) + #2598 (presenter env). Consider closing after #2599 lands.

Harness verification (2026-05-26 backlog-architect)

Repro on master via ./script/docker-exec.sh (php-compiler:22.04-dev):

make bootstrap-loop-probe          # exit 0 — M3 strict + M4 gen-2 native slice
make bootstrap-loop-gen1-link      # emit_path=native; gen-2 stdout: compiler smoke
BOOTSTRAP_M4_GEN2_STRICT=1 make bootstrap-loop-gen1-link  # native, no Zend fallback
./script/north-star4-verify.sh --strict  # OK

Closing as fixed on master — remaining gaps tracked in #2611 (script defaults without Makefile env) and #2600 (gen-1 compiles bin/compile.php spine, not loop smoke slice only).

Parent #1492 updated.

Verified green on master 2026-05-26; follow #2611 / #2600 for remaining M4/M5 scope.

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Self-host M4: bootstrap_loop gen-2 native emit — parseAndCompile returned null #2560

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Harness verification (2026-05-26 backlog-architect)

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Self-host M4: bootstrap_loop gen-2 native emit — parseAndCompile returned null #2560

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PurHur commented on May 26, 2026

PurHur commented on May 26, 2026

Harness verification (2026-05-26 backlog-architect)

PurHur commented on May 26, 2026

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