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- VulkanRenderer::CurrentXfbCounterSlot keyed m_xfbCounterSlotByObject on
GetBoundTransformFeedbackName(). glGenTransformFeedbacks hands a deleted name
straight back (IndexGenerator is LIFO) and nothing ever removed a map entry, so
a transform feedback object created on a recycled name was served the DEAD
object's counter group - and with it that group's m_xfbCountersValid and
m_xfbLastSeenGeneration entries, which are the resume/fresh decision for
vkCmdBeginTransformFeedbackEXT. This is D21 in plan B v2 4.7.3, the one entry
in that table whose today-key "guards nothing", and 10.4-5 asks for it to land
on dev on its own - hence this separate commit, kept in files no other commit
on this branch touches so the cherry-pick applies unaided.
- Frontend: TransformFeedbackObjectState gains a never-reused `lifetimeId`
through a default member initialiser, so every route into existence
(operator[] materialisation, `= {}` in GenTransformFeedbackNames and
CreateTransformFeedbackObject) mints a fresh one and a recycled name cannot
carry the dead object's id back. The allocator is the same shape as
BufferObject::AllocateLifetimeId (atomic, starts at 1 so a zeroed backend slot
is never a live object).
- The bound object's id is mirrored in m_boundTransformFeedbackLifetimeId,
refreshed by RestoreBoundTransformFeedbackState - which every bind, and the
revert that deleting the bound object performs, goes through - and seeded for
the default object by the GLContext constructor. GetBoundTransformFeedback
LifetimeId is therefore a const load. Reading it through operator[] instead
would have been an INSERT on the per-draw path, and UnorderedMap is
ska::flat_hash_map, whose rehash invalidates every reference into the
container, not just its iterators.
- Backend: the UnorderedMap is replaced by a fixed 16-entry owner table, which
fixes the second half of the same defect - the map was keyed on a value that
recycles yet was never pruned, so it grew for the life of the context. With
lifetime ids as keys a map would have grown without bound instead, so the
bounded table is required, not cosmetic.
- Slot exhaustion: past sixteen owners a group has to be taken over, and the
victim is chosen among owners with NO OPEN SPAN, which
GLContext::HasOpenTransformFeedbackSpan answers; an identity no live object
carries any more answers false, and that is what lets a dead owner's group
come back. Least-recently-used ALONE would have been exactly the wrong rule:
GL only permits another object to capture while this one is PAUSED, so the
paused span these groups exist to protect is by construction the least
recently used entry, and an LRU takeover would reset the one resume offset
that still matters. LRU is now only the tie-break among reclaimable groups.
Sixteen genuinely open spans at once is reported (MGLOG_E_ONCE) rather than
resolved silently, because whatever is taken then restarts at offset 0.
- Not done, and why: the natural place to hand a group back is
glEndTransformFeedback, but registering DirectVulkan's EndTransformFeedback
table entry would flip the test FixupGsStripCaptureOrder makes of that same
pointer (GL_Drawing.cpp:1255) to decide whether the backend already captured
in GL's vertex order, silently disabling the geometry-stage strip fixup for
DirectVulkan. Giving that discriminator a name of its own is a separate
change; until then the no-open-span rule is what keeps the table honest.
- CurrentXfbCounterSlot asserts the identity is never 0. Zero is the free-slot
sentinel, so an identity of 0 would match every free slot as "mine" without
ever claiming one - this bug reintroduced, with no symptom at the call site.
- TransformFeedbackLifetimeIdTest, in its own translation unit, pins the
frontend halves: an object created on a recycled name must not report the dead
object's id, the default object has an identity before anything binds it, and
a PAUSED span still reads as open while another object is bound and capturing
- which is the whole correctness argument for the eviction rule. The name
reuse is not simulated: the test asks the real generator and skips (loudly) if
it never recycled. Still untested: the >16-owners path itself, which needs a
backend scenario with seventeen capturing objects and there is none.
- Negative controls, each applied then reverted: making a non-bound object's
span read as closed reddens APausedSpanStaysOpenWhileAnotherObjectCaptures;
making a vanished identity read as open reddens the same case on its delete
assertion; dropping the constructor's seeding reddens
AnObjectAtARecycledNameCarriesAFreshLifetimeId.
- Tested: cmake --build build-linux -j 24 (clean, 166 targets); ctest -L unit
-j 12 -> 1386/1386 passed; ctest -L integration-gpu -> 866/866 passed
serially, and 866/866 on one of two -j 8 runs. The other -j 8 run failed
DirectGLES.PointSizeDemotionScenario.TheDemotionIsActuallyArmedWhenTheEnviron
mentPinsItOn, a member of the pre-existing parallel-ctest flake family: it
passes in isolation here, and the unmodified parent tree
(~/w7/p0-noop-wins-base) reproduces the same family under -j 8.