mesa-panvk-bifrost r7: fix XFB store channel-extract for packed varyings (iter19) #96
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Reference: marfrit/marfrit-packages#96
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Summary
0007-panvk-bifrost-xfb-component-base-fix.patchtomesa-panvk-bifrost(iter19)vkCreateGraphicsPipelinefor any XFB-bound vertex output declared with non-zerolayout (component=N)dEQP-VK.transform_feedback.simple.holes_verton Mali-G52 r1 MC1 (PAN_ARCH 7)Test plan
pacman -Syu mesa-panvk-bifroston consumer (ohm) reports r7Note:
max_output_components_{64,128,256}were never reached on the r5 sweep (watchdog killed transform_feedback after holes_vert crashed). Post-r7 they now run and surface their own pre-existing coredumps — confirmed on shipped r6 too. Not regressions from this patch. iter20+ territory.Cross-refs:
~/src/panvk-bifrost/iter19/phase{0,1,2,3}_holes_vert*.mdon the working tree.🤖 Generated with Claude Code
Co-Authored-By: Claude Opus 4.7 noreply@anthropic.com
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>