[sanxchep]

What

PositionExportLayout removes the guest's PA_CL_VS_OUT_CNTL position export bits only when decoding proves they are unused. When optional inspection reaches an unimplemented opcode in a padded program tail, it keeps those bits. Other decoder errors still propagate, and shader compilation is unchanged.

Add a regression case for the undecodable tail alongside the existing position export checks. Found during My First Gran Turismo (PPSA24156) bring-up. This change does not make the game playable.

Tested

• Rebuilt agc_driver_vertex_clip_cull_draw_tests on a branch based on current main.
• ctest --test-dir build --output-on-failure -R '^agc_driver_vertex_clip_cull_draw': 2/2 passed, including the no-key variant.
• python3 tools/check_conventions.py --base origin/main: passed.
• Ubuntu 24.04.5 LTS, x86_64, Linux 7.0.0-38-generic; MSI Katana 17 B13VGK, Intel Core i9-13900H, 32 GB RAM.
• NVIDIA GeForce RTX 4070 Laptop GPU (8188 MiB, driver 595.84) ran the Vulkan tests. Intel Iris Xe Graphics is present but was not tested.
• The isolated branch was not run against the full title; PPSA24156 still needs separate graphics fixes.

Checklist

• Based on current main; no other open PR implements the same functions
• One topic per PR; follow-ups go in a new PR
• No comments in code except technical debt
• Unimplemented paths throw; this fallback only retains guest metadata when optional export inspection cannot decode the tail
• No notes, investigation .md files or images added to the repository
• New third-party code is a submodule built from source (none added)
• Generic behaviour, not specific to one title
• Depends on: none
• Unblocks: none; PPSA24156 still needs other fixes
• GPUs tested: NVIDIA GeForce RTX 4070 Laptop GPU, driver 595.84, Ubuntu 24.04.5 LTS; Intel Iris Xe not tested
• AI-assisted: yes

[github-actions]

Some comparisons could not be completed because a pull request conflicts with the base branch. Review these shared files manually before concluding that there is no overlap.

Pull request	Shared files not compared
PR 5115	core/libs/prx/libSceAgcDriver/Execution/src/Driver/Shaders/ShaderRegistry.cpp
PR 5431	core/libs/prx/libSceAgcDriver/Execution/src/Driver/Shaders/ShaderRegistry.cpp
PR 6188	core/libs/prx/libSceAgcDriver/Execution/src/Driver/Shaders/ShaderRegistry.cpp
PR 6612	core/libs/prx/libSceAgcDriver/Execution/src/Driver/Shaders/ShaderRegistry.cpp
PR 6867	core/libs/prx/libSceAgcDriver/Execution/src/Driver/Shaders/ShaderRegistry.cpp
PR 6946	core/libs/prx/libSceAgcDriver/Execution/src/Driver/Shaders/ShaderRegistry.cpp
PR 6947	core/libs/prx/libSceAgcDriver/Execution/src/Driver/Shaders/ShaderRegistry.cpp
PR 6977	core/libs/prx/libSceAgcDriver/Execution/src/Driver/Shaders/ShaderRegistry.cpp
PR 7642	core/libs/prx/libSceAgcDriver/Execution/src/Driver/Shaders/ShaderRegistry.cpp
PR 7644	core/libs/prx/libSceAgcDriver/Execution/src/Driver/Shaders/ShaderRegistry.cpp