iter12 hit a wall: Brave's ANGLE-Vulkan path requires GLES3, which
requires VK_EXT_transform_feedback, which PanVk-Bifrost did not
implement. This iter implements that extension, unlocking the full
ANGLE-Vulkan-on-Bifrost stack.
The implementation follows Panfrost-Gallium's well-validated XFB lowering
(nir_io_add_intrinsic_xfb_info + pan_nir_lower_xfb) wired into the PanVk
shader pipeline after nir_lower_io. Adds 4 XFB buffer address sysvals
plus per-draw num_vertices to the graphics sysval struct. Buffer state
is tracked on the cmd buffer; per-draw sysval upload populates either
the bound buffer's GPU address or PAN_SHADER_OOB_ADDRESS (memory-sink)
so XFB-capable pipelines used outside Begin/End survive without GPU
fault — the Panfrost-Gallium idiom from gallium/drivers/panfrost/
pan_cmdstream.c:1350.
Verified on PineTab2 (Mali-G52 r1 MC1, RK3566):
- /tmp/panvk-iter13/probe_xfb: 3 vertices captured byte-exact
- /tmp/panvk-iter13/probe_xfb_nodraw: XFB pipeline used without Bind/
Begin/End survives — DEVICE_LOST regression closed
- Brave 148 with --use-angle=vulkan: WebGL 2.0 (OpenGL ES 3.0) creates
cleanly, renderer reports
"ANGLE (ARM, Vulkan 1.2.335 (Mali-G52 r1 MC1), panvk)"
- chrome://gpu graphics feature status: Canvas/Compositing/OpenGL/
Rasterization/WebGL/WebGL2/WebGPU/Video Decode all hardware accelerated
Phase docs:
- ~/src/panvk-bifrost/phase4_iter13_close.md (build green)
- ~/src/panvk-bifrost/phase5_iter13_close.md (review fixes applied)
- ~/src/panvk-bifrost/phase6_iter13_close.md (Brave integration green)
pkgver bumped 26.0.6.r2 -> 26.0.6.r3; iter13 patch applied via
unified-diff (the 328-line change scope is past sed-of-individual-
lines territory). Sanity checks in prepare() verify the patch landed.
Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
