MobileGL/docs/Disaggregated/notes/p5e/reports/sb-v1.md

sb — set_shader_buffers: the binding-point tables cross the wire (P5e wave 2)

Branch p5e/sb, head b004e5dc, base f6cfcbd3 (wave 1). 25 files, +1708/-92, two commits: 1ebe6abe (wire + applier + route + client emitter + gates + tests) and b004e5dc (the four Espryt consumers).

Gate

step	result
build	rc=0
unit	2216/2216 (2206 at base; +10 new names, each with a pull-build skip twin)
isplit	111/111
gens	all 7 rc=0; check_doc_citations rc=0 with 3 pre-existing warnings in CONTRACT-P5.md
one SSBO/atomic	DirectGLES.Split.(AtomicCounter|ProgramPipeline) 5/5; DirectGLES.(SsboArrayLength|SsboArrayDynamicIndex|StorageBufferRegrow) 6/6
one XFB	Split\..*Xfb 11/11
A/B bit 13 cleared	MOBILEGL_PIPE_PUSH=0x1fff on integration-split: 111/111 — today's picture reproduced
strict	3/111 pass, identical to the base (red by design, CONTRACT-P5C §6)

Strict marker table, before and after — IDENTICAL, nine rows, same counts: GetFramebufferBindingSlot@Clear 45 · GetTextureUnitObject@Clear 22 · GetBoundVertexArray@DrawArrays 14 · GetImageTextureBinding@BindImageTexture 13 · GetTextureObject@CopyImageSubData 6 · GetProgramForDispatch@DispatchCompute 3 · ValidateProgramName@ShaderStorageBlockBinding 2 · GetTextureUnitObject@GenerateMipmap 2 · GetTextureUnitObject@ReadPixels 1. No GetBufferBindingPoint@* marker exists at this head, before or after. Every split scenario that binds an indexed buffer aborts on an EARLIER row — pg's GetProgramForDispatch or the allowlisted ValidateProgramName — so my family never gets to abort first. That is the baseline document's own "lower bound" property, and it is why red-once (a) had to be executed in a different, equivalent form (below). The A/B at 0x1fff on the unit lane has two failures, DirectGLESTextureSync.{UnitMemoRefusesToDriveATwinFromAnotherTexture, AnAttachmentOnlyTexturesParametersReachTheDriverWithNoSamplerView} (SanityTest.cpp:3112) — NOT this package's: they fail identically with the P5e tracker shutter reverted, and they are texture-unit-memo cases. The arm the gate asks for (integration-split) is green.

What changed, per file

Wire / apply — MGPipeTypes.h (MGPShaderBuffers::WritableMask → Uint32[3], POD 32→40, kMGPipeShaderBufferWritableMaskWords, MGPipeShaderBufferMaskHas/Set); PipeApply.h (ShaderBufferWritableMask[3][3]); PipeApply.cpp (MGPipeApplySetShaderBuffers bodied, ClearShaderBufferWindows, both resets); PipeRoute.{h,cpp} + Client/WireTables.cpp (op 38, both arms); Wire/PipeWireCodec.cpp (the decode arm applies; Class/Count bounded in the layout arm); CapsCodec.cpp (one static_assert).

Client — new MG_Impl/Pipe/ShaderBufferEmit.h; BufferState.h (NoteBindPointChanged / GetBindPointGeneration, push-only); GLState/Core.{h,cpp} (the two forwarders, and the DSA SetNamedTransformFeedbackBinding bump); GL_Buffer.cpp (the bumps in BindBufferBase_State / BindBufferRange_State); Tracker.h (bits 15/16/17 rewritten); PipeFill.cpp (wired constant, P5eFamilyIsLive, the two adapters, the validate order, the reset list); MG_Backend/Init.cpp (consumer bit 13, ID-106).

Backend — DirectGLES.cpp: ResolveBufferBindingSubsystemArm / BindingPointsComeFromRecords / SyncBufferBindingPointsByRecord (all file-local), the two call sites, MarkShaderStorageBuffersGpuWritten's deletion under a transport, SyncAtomicCounterBuffers' record arm, the UBO loop's point half.

Gates / tests — gen_pipe_dirty_surface.py (Touch prefix, control 6 re-pointed); DirtySurface.def (two rows + the undecided mark); MG_Test/Pipe/CMakeLists.txt; new ShaderBufferEmitTest.cpp (8 cases); TrackerTest.cpp (2); PipeCatalogueTest.cpp, PipeWireCodecTest.cpp, RemoteClientTest.cpp (the pins that invert).

ID-104: Uint32 WritableMask[3], not Uint64 + Uint32. 96 ≥ 84 either way, but ONE word type means one shift width, so the set and the test are a single expression each rather than a low half and a high half that have to agree — and the applier's per-class copy goes through the same two helpers as the payload's. POD 32 → 40, pinned in PipeCatalogueTest.

kimi-audit rows 111–124

row	site	verdict
111	SyncBufferBindingPoints point + GetBoundObject	RETIRED → SyncBufferBindingPointsByRecord
112	same: ensure probe, GetRange, obj->GetSize	RETIRED → EnsureBufferResourceForHandle(nullptr, Res), the record's extent, resource->storageSize
113	MarkShaderStorageBuffersGpuWritten	RETIRED BY DELETION under a transport; the client owns the set
114	SyncTransformFeedbackBindingPoints	LEFT BARRIERED (XFB, §5.7)
115	SyncAtomicCounterBuffers (count, point, ensure, range, mark)	RETIRED; its MarkBufferGpuWritten deleted
116	SyncBoundBuffer GetBufferBindingSlot	NOT MINE — the generic slot, FieldOwnership.def:78 (P8/P9/P13); untouched
117	UBO loop point + GetBoundObject + GetRange	RETIRED → BoundShaderBuffers[Uniform][binding]
118	UBO loop GetBufferResource / IsBufferDrawClean / EnsureBufferResource	RETIRED → the three by-handle twins
119–124	StartPendingTransformFeedback, ReadbackCapturedRanges, ScatterCapturedRecords	LEFT BARRIERED (XFB, §5.7)

Not found as written: nothing. MGPipeFrontendKeyedRegistryScope at Managers.cpp:2938 (HandleOfBuffer) is NOT retired by this package — the draw path no longer reaches it for binding points, but EnsureBufferResource / IsBufferDrawClean still do for the monolith arm and for other families.

Red-once, executed, reverted, quoted verbatim

(b) the shutter — reverted bits 15/16/17 to the pre-P5e content aggregate, rebuilt, ran:

../MobileGL/MG_Test/Pipe/TrackerTest.cpp:615: Failure
Expected: (m_tracker.LastDirty() & MGPipeDirtyBit(MGPipeDirty::NewConstBuffers)) != (0u), actual: 0 vs 0
NEW_CONST_BUFFERS did not fire when a uniform binding point moved onto another buffer - the emitted window would still name the first one
../MobileGL/MG_Test/Pipe/TrackerTest.cpp:624: Failure
Expected: (m_tracker.LastDirty() & MGPipeDirtyBit(MGPipeDirty::NewConstBuffers)) != (0u), actual: 0 vs 0
NEW_CONST_BUFFERS did not fire for an unbind
../MobileGL/MG_Test/Pipe/TrackerTest.cpp:652: Failure
Expected equality of these values:
  m_tracker.LastDirty() & family
    Which is: 229376
  0u
    Which is: 0
a write to a buffer bound to no binding point republished the binding-point sets

Both directions in one revert: the old shutter UNDER-fires on a rebind and an unbind and OVER-fires on an unrelated glBufferSubData (229376 = bits 15|16|17). Restored → 2/2 pass.

(a) the record arm. The brief's form is not executable at this head (see the strict table above, and §"rulings"). Executed the equivalent that IS available: keep the server's record arm and withhold the CLIENT's emission (kMGPipeWiredBufferBindingSubsystem back to 0), so the server's window is empty and nothing else can fill it:

0% tests passed, 5 tests failed out of 5
  3464..3466 DirectGLES.Split.AtomicCounterScenario.* (Subprocess aborted)
  3467..3468 DirectGLES.Split.ProgramPipelineScenario.* (Subprocess aborted)
[08:18:24] [Linux MobileGLIntegra/FATAL]: MGPipe: Fatal{UnimplementedWritebackWait} - a ClientSession is
active and buffer 1 still has an outstanding GPU write after its readback was emitted.

Restored → 5/5 pass. Also ran the mirror (BindingPointsComeFromRecords() → false, the frontend walk under a live wire): green picture, marker table unchanged — the finding in §2 of "rulings".

(c) the sticky forward. rsp is a process-wide residual-pull tally on the apply thread's stats line, not a per-field one, so the measurable form is the delta on DirectGLES.Split.AtomicCounterScenario (MOBILEGL_PIPE_STATS=1 MOBILEGL_PIPE_STATS_PERIOD=1):

=== AFTER (record arm live) ===   rsp values: 2 x rsp=196, 1 x rsp=588   (max 588)
=== BEFORE (frontend walk)  ===   rsp values: 2 x rsp=199, 1 x rsp=597   (max 597)

9 and 3 pulls per case removed — GetBufferBindingPointCount plus the per-point GetBufferBindingPoint reads of the counter walk. It does not reach 0 because other families still pull on the same thread.

(d) no double marking. The backend marks are deleted; the client's are the only producer. Withheld MarkShaderStorageBindings + MarkAtomicCounterBindings on the client:

0% tests passed, 3 tests failed out of 3
../MobileGL/MG_IntegrationTest/Scenarios/AtomicCounterScenario.cpp:186: Failure
Expected equality of these values:   Which is: 5   Which is: 13
../MobileGL/MG_IntegrationTest/Scenarios/AtomicCounterScenario.cpp:189: Failure
Expected equality of these values:   Which is: 100   Which is: 116

Restored → 3/3 pass, and SplitBufferTest's existing ProducerMarkCount(ShaderStorageBinding) == 1 / AtomicCounterBinding == 1 pins stay green (24/24). A revert of the backend DELETION cannot go red by construction — it is a duplicate — so this is the honest form of (d).

(e) the catalogue inverts. PipeCatalogue.{UninstalledTablesAreAllNull, ExactlyTheRoutedRowsAreInstalledAndTheRestAreStillNull} now assert SetShaderBuffers != nullptr; installed rows 34 → 35, the escape total 38 → 39, PipeRouting...EveryRoutedRowMoved 34 → 35.

G1 / G2 / G14

Every new client symbol is under MOBILEGL_PIPE_PUSH (BufferState's two members and the two GLContext forwarders included, so the pull build's objects do not resize) and every new server arm under MOBILEGL_BUILD_DISAGGREGATED, with the frontend arm kept token for token for Transport=monolith (ruling 1). The only shared-code deltas are MGPShaderBuffers' size (a push-only payload) and two static_asserts. 10 new ctest names, all with pull-build skip twins.

Seams I assumed

• pg owns currentProgram->GetUniformBlockBinding(i) (DirectGLES.cpp, the line above my arm). I index BoundShaderBuffers[Uniform][binding] with its result and did not touch it; if pg moves the binding source to MGPipeShaderCsoRecord::BlockBindings, binding keeps its meaning and my arm is unaffected.
• fb owns the third GPU-write mark, MarkWritableImageBufferTexturesGpuWritten (DirectGLES.cpp, kimi row S3). I deleted my two under a transport and left it; the brief calls the pair "one edit split across two files".
• ra flips kMGPipeP5eClientWaitRuleLanded. SetShaderBuffers is kWaitNone in c0e's static column, so it goes fire-and-forget on that day with no change here.
• tx2 / fb own the rows that abort ahead of mine in the strict lane.

Rulings I need

1. GetBufferBindingPointCount's forward → FATAL under split (§5.6, §8.8) CONFLICTS WITH §6. MG_Backend/DirectVulkan/Renderer/UniformManager.cpp:1200 and :2030 are live Magma readers, FieldOwnership's class is unconditional, and §6 keeps Magma's P5C semantics — so the flip would abort a split Magma server. I left both rows BARRIER_PULLED and removed Espryt's only caller instead (the measured rsp drop above). A backend-keyed class would be a new mechanism and an integrator ruling.
2. Red-once (a)'s scenarios do not exist in the split lane. SsboArrayDynamicIndexScenario, StorageBufferRegrowScenario and SsboArrayLengthScenario carry only integration-gpu; there is no DirectGLES.Split. twin. In the split scenarios that DO bind indexed buffers the strict lane aborts on pg's row first, so Fatal{UnmigratedPipeInput, "GetBufferBindingPoint@DrawVbo"} is unreachable until tx2/fb/pg land. Re-run this red on the integrated tree (BRIEF §3.5) — it should be reachable there.
3. The sink named in the brief does not exist. MG_Remote/Server/PipeApplier.cpp's ServerVerbSink has methods for the five class-B VERBS only; a kCtxState row's sink is the decode arm in MG_Remote/Wire/PipeWireCodec.cpp. I extended scope to two arms of that file (the decode case and the layout bound). pg will touch the neighbouring SetProgramBindings case — separate case labels, so the merge is textual only.
4. PipeFill.cpp needed a conjunct outside the named ranges. P4aFamilyHasItsConsumer asks R-8 for the RESOURCE bit and answers true for any non-P4a family, so ID-106's consumer bit 13 would have had no reader. I added P5eFamilyIsLive (bit 13's own R-8 question + bit 13 requires bit 7) beside it and one conjunct in FamilyIsLive and in wants().
5. CONTRACT-P5E.md §5.6 still says the WritableMask question is "an integrator ruling sb must ask for rather than pick". ID-104 answered it; the landed contract text wants that paragraph replaced at landing. I did not edit c0e's file.
6. Fatal{ProtocolCorruption, "SetShaderBuffers.Class"} is spelled in the file's existing shape (Fatal{ProtocolCorruption} SetShaderBuffers.Class - …, as ApplyUnitWindow spells its own), not with the contract's comma-and-quotes. Say if the contract's literal form is wanted.

What I did not do

• The program-derived set_shader_buffers window (BRIEF §5, trailing): the window is the touched high-water mark, per ruling 10. A program binding block 0 at GL point 83 still pays an 84-entry record on its first emission after a bind.
• set_stream_output_targets stays unemitted and XFB stays lockstep (§5.7). Dirty bit 17 is computed, shutters correctly on the new generation, and names the subsystem.
• FieldOwnership.def:80-81 stays BARRIER_PULLED with phase "P5e (Espryt unbarriered), P7 (Magma)": Magma still reads GetBufferBindingPoint, so the four consumers are not all gone.
• No PipeStats::CallClass row for binding-point emissions — that would grow the counter arrays and the stats line for every build. The emitter keeps its own per-class tally (EmissionCount(cls)), which is what the unit suite reads.