kAsyncShaderCompileDefault flips to true, which also advertises
GL_KHR_parallel_shader_compile by default on both backends. Unset
MOBILEGL_ASYNC_SHADER_COMPILE now resolves to ON; =0 remains the complete kill
switch (reverts the threading and withdraws the extension together).
The gate behind the flip (headless Mesa - llvmpipe for Espryt, lavapipe for
Magma - at c6299f75): GL30/31/32/33/40 mustpass plus the
KHR-GL46.parallel_shader_compile group, both backends, async=1 with the
extension advertised. 58,344 case-runs, 8 failures - and every one of the 8
also fails standalone at async=0, in the full async=0 suite arms with an
identical per-case failure set, and under the pre-P1-stage-6 library. Zero
async-attributable deltas; the 8 are Mesa-upgrade drift (4 unique signatures:
Espryt GL40 transform_feedback.draw_xfb{,_feedbackk}_test, Magma
texture_size_promotion.functional + packed_pixels rgb9_e5_format_red on
GL32/33/40), recorded for separate follow-up.
Validation under the flipped default (no env var): 553/553 unit at the default
AND with the kill switch; parallel_shader_compile 3/3 on both backends proving
the default advertises; 44+44 integration scenarios; 71/72 CI trace-replay
fixtures (the one failure is the pre-existing create-indirect lavapipe crash,
identical under the pre-fix library). The lifecycle test's contract updates
with the default: AsyncIsOnByDefaultAndTheOverrideDecidesEitherWay.
Not covered by this gate and deliberately left open: SSO/DSA suites (GL41+,
separate follow-up per review), and real-driver confirmation on NVIDIA/Mali -
the Mali-G77 on-device sweep runs separately as a report-only pass.
glCompileShader with MOBILEGL_ASYNC_SHADER_COMPILE=1 snapshots its inputs on
the GL thread (source SharedPtr, CompileEnv, cache handle) and runs the whole
pure pipeline - preprocess, validators, extractors, glslang parse - as a
ShaderCompileTask on the worker pool, returning immediately. Every read of
compile-produced state joins through the single Compiled() gate; links stay
synchronous this stage and join their attached shaders at the top of the
body. Flag off, the path is the same code run inline.
Mechanics: the job node owns all its inputs (no back-pointer, no lifetime
tie to the shader object), so re-sourcing or deleting a pending shader is
cancel-and-drop, never a wait; glslang worker hygiene is a TLS-allocator
scope guard plus GL-thread builtin prewarm (gated on the flag, latch reset
on Destroy so re-initialization re-warms); worker-side diagnostics defer
through the job and replay on the GL thread at the join, enforced by
IsPoolThread asserts in RecordError and an empty-deferred-errors tripwire.
A body that throws publishes a COMPLETE failed compile (status false, real
info log) rather than an abandoned node, and never memoizes away the retry;
a failed enqueue (OOM) cancels the node instead of stranding the joiner -
including inside the dispatch loop, where the in-flight slot is repaid.
The pool StopAndDrains from an atexit sentinel too: workers still inside
glslang parse while exit() ran static destructors was a real 2-in-5 SIGSEGV,
reproduced and fixed (15/15 clean after).
Backend-internal shader objects (default FS, DirectVulkan blit/mipmap) are
cache-less and always compile inline - compile-and-read-in-one-breath needs
no round trip.
Gates: unit suite 488/488 with the flag off AND on (x5); AsyncCompileTest
(12 e2e cases: pending re-source/delete/recompile, byte-identical failure
logs across modes, 48-compile cache stress) x10 repeats clean both modes;
full NVIDIA DirectGLES retrace identical result sets flag off/on (zero new
deltas); compile-phase timing flat as designed (links still serial - the
parallel win arrives with stage 4's async link + stage 5's
KHR_parallel_shader_compile).
Standalone Asio (submodule, asio-1-38-2 @ 8806a680, ASIO_STANDALONE +
ASIO_NO_DEPRECATED, header-only - no linked artifact) and the job machinery
the async shader pipeline will run on: JobNode (state machine with deferred
errors, continuations firing exactly once, dependency counters, cancel
semantics split into request vs outcome) and ShaderCompilePool
(asio::thread_pool behind a pimpl so no header leaks asio; big-core count
via cpufreq at >=85% of peak clamped to [1,4]; lazily constructed, so with
the flag off no worker thread ever exists; StopAndDrain leads DestroyImpl).
MOBILEGL_ASYNC_SHADER_COMPILE / _THREADS config knobs, default OFF. Nothing
in the GL pipeline references the pool yet - grep-verified; the full
DirectGLES retrace and compile benches are byte- and time-identical. 25
threaded unit tests, clean across 20x gtest_repeat.
Swung0x48