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`unaligned-atomic-buffer-range@P7`, `unaligned-storage-buffer-range@P7` and
`unaligned-texel-buffer-range@P7` become named declines (rule I (a)). The two
offset-overflow guards next to them keep their named Fatal under their own words:
those are arithmetic that cannot happen, not shapes an application can bind.
The atomic-counter one is the only member of this cluster an application can
actually reach, and it is a real live gap, not a hypothetical. GL 4.6 core 6.1.1
gives GL_ATOMIC_COUNTER_BUFFER no queryable offset alignment, so
ValidateBufferRangeOffsetAndSize only enforces offset % 4 on it - while glslang
lowers every atomic_uint onto a synthesized storage block whose descriptor offset
must be a multiple of minStorageBufferOffsetAlignment (16 on lavapipe, 64 on
Adreno). `glBindBufferRange(GL_ATOMIC_COUNTER_BUFFER, 0, buf, 4, 4)` is a legal
GL bind that this backend cannot express, and it used to take the session with
it. The plain SSBO and texel halves are unreachable by comparison:
GL_SHADER_STORAGE_BUFFER_OFFSET_ALIGNMENT and GL_TEXTURE_BUFFER_OFFSET_ALIGNMENT
are published from the same Vulkan limits, so the frontend already answers
GL_INVALID_VALUE.
DECLINED RATHER THAN COPIED, and this is the package's one real design choice.
Copying the window into an aligned transient slice reads correctly and then
silently DROPS every shader write. This site cannot tell a writable storage block
from a read-only one - there is no readonly bit in the storage-block reflection,
an atomic counter is written by definition, and MarkWireBufferGpuWritten right
below already assumes any binding here may be written. A correct copy needs a
post-dispatch copy-back from the transient slice to the unaligned source, ordered
with a barrier, and the place to record that is the draw/dispatch tail in
VulkanRenderer.cpp / WireDraw.inc - wave-2 packages B and C, not this file.
Returning stale counters with no error is worse than losing the dispatch with a
named line in the role log. notes/p7/magma-a.md carries the recipe for whoever
holds those files.
The texel half keeps the draw where it safely can: a read-only buffer texture
falls back to the same placeholder view an unbound one gets (zeros, which is what
a missing view gives in monolith), while a writable imageBuffer declines - the
placeholder is shared by every unbound binding, so absorbing real stores into it
would alias other bindings as well as lose the writes. Copying is not available
there either: the transient arena carries no {UNIFORM,STORAGE}_TEXEL_BUFFER
usage, so no VkBufferView can be made over it, and widening a shared per-frame
allocation to buy an unreachable path is the wrong trade.
red-once (R-16), a reachable case this time, all three Magma two-process arms:
DirectVulkan.{Split,Spawn,Tcp}.Buffers.F1WireScenario.UnalignedAtomicCounterRangeDeclinesAndTheSessionLives
before Subprocess aborted - Fatal{UnmigratedVerb, "Magma:unaligned-atomic-buffer-range@P7"}
after 3/3 Passed, and the role log carries
"block 'gl_AtomicCounterBlock_0' is bound at offset 4, which is not a
multiple of this device's minStorageBufferOffsetAlignment (16);
atomic-counter ranges cannot be expressed as a descriptor ... DECLINED
(unaligned-atomic-buffer-range)"
The case pins the decline's whole observable: the bind raises no GL error, the
dispatch does not run, every byte of the counter buffer is unchanged, and the
context still serves ordinary work afterwards. A future copy-back turns one
EXPECT into seed[1] + 1 and leaves the rest standing.
Lanes: integration-magma-split 75/75, -spawn 54/54, -tcp 56/56,
integration-magma-buffers 21/21.