Adds tests/PushConstantRewrite, a host test that compiles representative
ray-generation shaders with glslang, runs the real WorkaroundNvidiaAS::Patch
over them, and asserts with spirv-val (the same invocation vkCreateShaderModule
uses) that the result is valid and contains exactly one push-constant block —
covering both the merge path (shaders that already declare a push constant,
including mat4/vec3/uint, a lone uint, and an array layout) and the synthesize
path, plus a no-op case (push constant but no AS read). It also checks the
published TLAS push offset for each layout.
The workaround namespace is exported so the test can drive Patch directly; both
go away with the rest of the workaround. project.cpp wires the test as an
executable that recompiles the module and requires glslang + spirv-val.
Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
The NVIDIA descriptor-heap AS-read workaround (#15) rewrote heap
acceleration-structure reads into a load of the TLAS device address from
a push-constant block. It always *synthesized a new* push-constant block,
so any ray-tracing shader that already declared one ended up with two —
which SPIR-V forbids ("at most one push constant block statically used per
entry point"), and vkCreateShaderModule's spirv-val check rejected:
Entry point id '4' uses more than one PushConstant interface.
WorkaroundNvidiaAS::Patch now detects an existing PushConstant variable and,
when present, appends a single ulong member (the TLAS address) to that
block instead of adding a second one, reading the address through the
shader's own push-constant variable. The append offset is the end of the
user's block, computed from the members' explicit Offset/ArrayStride/
MatrixStride decorations (correct under both scalar and std140 layout) and
rounded up to 8. Shaders with no push constant of their own keep getting a
freshly synthesized single-member block at offset 0, exactly as before.
That offset is published via Device::workaroundTlasPushOffset and RTPass
feeds it to vkCmdPushDataEXT so the address lands where the rewritten load
reads it (0 for the synthesized case, preserving prior behaviour).
Verified on the affected driver (NVIDIA 610.43.02, RTX 4090): VulkanTriangle
ray-traces correctly and validation-clean both with and without a
user-declared raygen push constant.
Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
