Adds 0007-panvk-bifrost-xfb-component-base-fix.patch — eliminates a
reliable SIGSEGV in vkCreateGraphicsPipeline whenever an XFB-bound
vertex output is declared with non-zero `layout (component=N)`.
Surfaced by dEQP-VK.transform_feedback.simple.holes_vert (Mali-G52 r1
MC1, PAN_ARCH 7). Backtrace lands 11 frames into libvulkan_panfrost.so
called from vkt::TransformFeedback::TransformFeedbackHolesInstance::
iterate.
Root cause: iter17's lower_xfb_output_iter17 (and upstream
pan_nir_lower_xfb, which has the identical `// TODO`) computes the
source-channel mask as `mask << channel_idx`, where channel_idx is
the varying-location component (0..3) but src only contains channels
starting at nir_intrinsic_component(intr). For a scalar declared
component=2, the lowering computed `mask << 2` against a 1-component
src — out-of-range; the malformed nir_def segfaulted in downstream
NIR constant-folding (nir_constant_expressions.c::evaluate_*).
Fix translates channel_idx to source-channel space by subtracting
nir_intrinsic_component(intr) before shifting the mask, and replaces
the elided release-mode asserts with explicit release-mode guards
(closes the same elision class as the original bug).
Verified on PineTab2 (Mali-G52 r1 MC1, PAN_ARCH 7) against vulkan-cts
1.3.10.0:
- holes_vert / holes_extra_draw_vert no longer SIGSEGV (now Fail
on color-check; that is a separate iter20 finding).
- basic_*: 36/36 Pass. depth_clip_*: 1 Pass + 4 NotSupported.
lines_or_triangles*: 16 NotSupported. 0 Fail across the set.
Caveat (not regressions): max_output_components_64/_128/_256 were
never reached on the r5 sweep — watchdog killed transform_feedback
after the holes_vert crash. With this fix in place, they now run
and surface their own pre-existing coredumps, confirmed on shipped
r6 baseline too. iter20+ territory.
Phase 5 (2nd-model) review: APPROVE WITH CHANGES (non-blocking).
Changes applied: release-mode defensive guards on both preconditions
plus a dispatcher-side comment clarifying the i*2+j semantics.
Cross-refs:
- ~/src/panvk-bifrost/iter19/phase{0,1,2,3}_holes_vert*.md
Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>
marfrit