No pre-rasterization stage writes Layer: vertex layer exports are
ignored, so the first layer is used and the render target index field
of the packed ancillary word is 0. The lowering read the Layer builtin
for it instead. AMD's Windows driver drops the color writes of a
fragment shader that consumes an unwritten Layer, which made
agc_driver_relative_ancillary fail on AMD hardware (#4800); lavapipe
returns 0 there.
Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
main reads target.vertexSubgroups at request version 18 since #4470, so
reading the pixel primitive class at 18 as well read a version 18
request written by main one byte short. The class is now written and
read at version 19. agc_shader_memory loads a version 18 request as
main writes it, and it fails with "truncated data" when the class is
read at 18.
The composed word no longer reads the Layer builtin for bits 16-28.
Draws render to a single layer and guest layer exports are ignored, so
no stage writes Layer, and AMD's Windows driver drops the writes of a
fragment shader that reads it unwritten (#4800). The field is the
constant 0 and pixel_ancillary checks that the composed program has no
Layer read. The debt entry names the bits that have no source and are
assumed zero (2-7, 12-15, 29-31), and says that a change which makes
draws export a layer must restore the read.
A packed ancillary word that still reaches an export, or any other read
the masked-select pass cannot drop, no longer stops the recompile. After
that pass every remaining use gets the composed word: the primitive class
at bits 0-1, SampleId at bits 8-11 and Layer at bits 16-28, with every
other bit zero. Those lanes do export the ancillary VGPR on the console,
so the word has to be right, not just present.
The primitive class (0 point, 1 line, 2 triangle, 3 rectangle) comes from
the draw. RasterPrimitiveOf maps rect lists to 3, line lists on the vertex
path to 1 and everything else the driver accepts to 2, because its
geometry and tessellation paths only output triangles. It reaches the
shader as pipeline specialization constant 8233, the way dual-source
blending does: a request field that is folded into the specialized
module and is part of the result memo, the draw key and the serialized
request (version 17).
Only shaders that read the class pay for it. ShaderInfo records the read
(disk cache format 28), and only those shaders put the class in their
module key, so a shader that reads just the sample or layer field keeps
one module for every primitive class. The draw sets the class only when
the pixel shader loads the ancillary VGPR, so other draws keep the draw
cache entries they have today.
The VRS rates (bits 2-5) and the eye id (bit 7) are 0 because the driver
supports neither VRS nor multiview. SampleId is 0 because the driver
rejects MSAA and per-sample shading, and Layer is 0 while it ignores
vertex layer exports. TechnicalDebt.md records the layout sources and
these assumptions.
Tests:
- pixel_ancillary builds an export to target 0 whose two channels select
between a packed value and a phi carrying the word. It checks the word
for each primitive class, sample and layer, checks that the three
shapes the masked-select pass keeps now compile with the composed word,
and that a program whose select the pass drops reads no class.
- agc_driver_pixel_ancillary_word exports the word from a draw and reads
back 2, 3 and 1 for triangle, rectangle and line. A shader that reads
only the sample field shares one module across the classes, and the
whole-word shader gets one per class. It also checks RasterPrimitiveOf.
- agc_shader_memory covers the version 17 round trip, and
agc_shader_disk_cache the new flag.
Both ancillary tests fail with the old refusal when the composition is
disabled.
Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Vulkan starts only quads holding a non-helper lane, so the bit is set in every
lane it runs. Stray's pixel shader 0x2012f90000 keeps the packed ancillary
word where that bit is clear, and failed with an unsupported live use.
(cherry picked from commit 2068089b3d75fae55d0994a0916a22bffd7ee2a4)
A descriptor dword built by S_BREV_B32, V_BFREV_B32 or S_BREV_B64 from a
constant stayed a runtime value, so the resource could not be resolved
and the shader failed to prepare. The constant folder now reverses the
bits of an immediate the way the hardware does (D[31-i] = S0[i]), like
the existing BitCount32 fold. ConstantBitTest covers the fold.
Co-Authored-By: Claude Haiku 5.5 <noreply@anthropic.com>
A select of exec and zero gives a mask that is the same for every lane. Reading
it back went through a lane number, which Metal does not have in a vertex
shader, so MoltenVK rejected the shader. The select now stores the lane bit and
marks the pair as a mask, a constant mask word reads as a constant, and the
constant folder removes the bit test on an all-zero or all-one word.
agc_scalar_select_mask runs the translated IR over a wave and pins the lane
values for scc set and clear, a source that differs per lane, the two wave64
halves differing, a destination that is also a source, and constant and
literal sources.
Co-Authored-By: Claude Sonnet 5.5 <noreply@anthropic.com>
A use of the packed ancillary VGPR other than a constant field extract (the word passed through a
select before its sample number is extracted) reads the word rebuilt from the sample number (bit 8)
and the render target index (bit 16). Extracts of other bits straight from the word stay refused, and
the refusal now names the uses.
Co-Authored-By: Claude Opus 5.5 (1M context) <noreply@anthropic.com>
Any other live use of the packed register keeps throwing, as on main, instead of
reading SampleId << 8 | Layer << 16 with the other bits zero. The field range
check no longer underflows for an extract that starts past a field's end.
Adds the pixel_ancillary recompiler test.
Co-Authored-By: Claude Opus 5.5 (1M context) <noreply@anthropic.com>
Bit-field extracts of the packed ancillary VGPR become gl_SampleID and gl_Layer reads. A pixel
shader reading gl_Layer needs the Geometry capability instead of ShaderLayer and SPIR-V 1.5, and
the Geometry capability is available whenever the geometryShader feature is. 32-bit
SPI_SHADER_Z_FORMATs and 32_ABGR are accepted with the depth and sample-mask export enables.
Co-Authored-By: Claude Opus 5.5 (1M context) <noreply@anthropic.com>
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