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Add RT acceleration structure abstraction with size queries and resource allocation
Introduce the foundational types for ray tracing acceleration structures: abstract `AccelerationStructure` base class, geometry/instance descriptors, BLAS/TLAS build-request structs with size queries, and AS resource allocation across DX12, Vulkan, and Metal backends. Recording the actual build commands lands in a follow-up commit on top of the ComputeEncoder abstraction. Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>
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9 files changed

Lines changed: 988 additions & 41 deletions

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‎include/API/AccelerationStructure.h‎

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//===- AccelerationStructure.h - RT Acceleration Structure Types ----------===//
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//
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// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
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// See https://llvm.org/LICENSE.txt for license information.
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// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
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//
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//===----------------------------------------------------------------------===//
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#ifndef OFFLOADTEST_API_ACCELERATIONSTRUCTURE_H
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#define OFFLOADTEST_API_ACCELERATIONSTRUCTURE_H
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#include "API/API.h"
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#include "API/Buffer.h"
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#include "API/Resources.h"
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#include "llvm/ADT/ArrayRef.h"
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#include "llvm/ADT/SmallVector.h"
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#include "llvm/Support/Error.h"
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#include <cstdint>
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namespace offloadtest {
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enum AccelerationStructureBuildFlags : uint32_t {
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BuildFlagNone = 0,
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AllowUpdate = 1 << 0,
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PreferFastTrace = 1 << 1,
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PreferFastBuild = 1 << 2,
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};
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inline AccelerationStructureBuildFlags
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operator|(AccelerationStructureBuildFlags A,
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AccelerationStructureBuildFlags B) {
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return static_cast<AccelerationStructureBuildFlags>(static_cast<uint32_t>(A) |
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static_cast<uint32_t>(B));
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}
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inline AccelerationStructureBuildFlags
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operator&(AccelerationStructureBuildFlags A,
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AccelerationStructureBuildFlags B) {
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return static_cast<AccelerationStructureBuildFlags>(static_cast<uint32_t>(A) &
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static_cast<uint32_t>(B));
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}
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struct AccelerationStructureSizes {
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uint64_t ResultDataMaxSizeInBytes = 0;
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uint64_t ScratchDataSizeInBytes = 0;
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uint64_t UpdateScratchDataSizeInBytes = 0;
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};
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struct TriangleGeometryDesc {
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Buffer *VertexBuffer = nullptr;
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uint64_t VertexBufferOffset = 0;
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uint32_t VertexCount = 0;
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uint32_t VertexStride = 0;
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Format VertexFormat = Format::RGB32Float;
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Buffer *IndexBuffer = nullptr;
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uint64_t IndexBufferOffset = 0;
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uint32_t IndexCount = 0;
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IndexFormat IdxFormat = IndexFormat::Uint32;
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bool Opaque = true;
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};
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struct AABBGeometryDesc {
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Buffer *AABBBuffer = nullptr;
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uint64_t AABBBufferOffset = 0;
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uint32_t AABBCount = 0;
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uint32_t AABBStride = 24;
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bool Opaque = true;
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};
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class AccelerationStructure;
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struct AccelerationStructureInstance {
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float Transform[3][4] = {{1, 0, 0, 0}, {0, 1, 0, 0}, {0, 0, 1, 0}};
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uint32_t InstanceID = 0;
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uint8_t InstanceMask = 0xFF;
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AccelerationStructure *BLAS = nullptr;
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};
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struct BLASBuildRequest {
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llvm::SmallVector<TriangleGeometryDesc> Triangles;
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llvm::SmallVector<AABBGeometryDesc> AABBs;
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AccelerationStructureBuildFlags Flags = BuildFlagNone;
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AccelerationStructureSizes Sizes;
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};
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struct TLASBuildRequest {
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llvm::SmallVector<AccelerationStructureInstance> Instances;
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AccelerationStructureBuildFlags Flags = BuildFlagNone;
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AccelerationStructureSizes Sizes;
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};
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inline llvm::Error validateTriangleGeometryDesc(const TriangleGeometryDesc &D) {
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if (!D.VertexBuffer)
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return llvm::createStringError(
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std::errc::invalid_argument,
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"TriangleGeometryDesc: VertexBuffer is null.");
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if (!isPositionCompatible(D.VertexFormat))
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return llvm::createStringError(
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std::errc::invalid_argument,
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"TriangleGeometryDesc: VertexFormat '%s' is not position-compatible.",
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getFormatName(D.VertexFormat).data());
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if (D.VertexStride < getFormatSizeInBytes(D.VertexFormat))
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return llvm::createStringError(
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std::errc::invalid_argument,
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"TriangleGeometryDesc: VertexStride (%u) must be >= format size (%u).",
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D.VertexStride, getFormatSizeInBytes(D.VertexFormat));
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if (D.VertexCount == 0)
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return llvm::createStringError(std::errc::invalid_argument,
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"TriangleGeometryDesc: VertexCount is 0.");
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if (D.IndexBuffer && D.IndexCount == 0)
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return llvm::createStringError(
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std::errc::invalid_argument,
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"TriangleGeometryDesc: IndexBuffer is set but IndexCount is 0.");
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if (!D.IndexBuffer && D.IndexCount != 0)
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return llvm::createStringError(
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std::errc::invalid_argument,
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"TriangleGeometryDesc: IndexCount is set but IndexBuffer is null.");
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if (D.IndexBuffer && D.IndexCount % 3 != 0)
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return llvm::createStringError(
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std::errc::invalid_argument,
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"TriangleGeometryDesc: IndexCount (%u) must be a multiple of 3.",
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D.IndexCount);
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if (!D.IndexBuffer && D.VertexCount % 3 != 0)
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return llvm::createStringError(
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std::errc::invalid_argument,
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"TriangleGeometryDesc: VertexCount (%u) must be a multiple of 3 when "
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"no index buffer is provided.",
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D.VertexCount);
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return llvm::Error::success();
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}
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inline llvm::Error validateAABBGeometryDesc(const AABBGeometryDesc &D) {
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if (!D.AABBBuffer)
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return llvm::createStringError(std::errc::invalid_argument,
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"AABBGeometryDesc: AABBBuffer is null.");
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if (D.AABBCount == 0)
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return llvm::createStringError(std::errc::invalid_argument,
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"AABBGeometryDesc: AABBCount is 0.");
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if (D.AABBStride < 24)
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return llvm::createStringError(
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std::errc::invalid_argument,
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"AABBGeometryDesc: AABBStride (%u) must be >= 24.", D.AABBStride);
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return llvm::Error::success();
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}
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inline llvm::Error validateBLASBuildRequest(const BLASBuildRequest &Req) {
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if (Req.Triangles.empty() && Req.AABBs.empty())
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return llvm::createStringError(
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std::errc::invalid_argument,
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"BLASBuildRequest: Must have at least one geometry descriptor.");
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// Vulkan and Metal forbid mixing triangle and AABB geometry in a single BLAS;
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// D3D12 technically permits it but is uncommon. Reject for portability.
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if (!Req.Triangles.empty() && !Req.AABBs.empty())
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return llvm::createStringError(
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std::errc::invalid_argument,
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"BLASBuildRequest: Cannot mix triangle and AABB geometry in a "
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"single BLAS.");
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for (const auto &T : Req.Triangles)
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if (auto Err = validateTriangleGeometryDesc(T))
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return Err;
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for (const auto &A : Req.AABBs)
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if (auto Err = validateAABBGeometryDesc(A))
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return Err;
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return llvm::Error::success();
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}
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inline llvm::Error validateTLASBuildRequest(const TLASBuildRequest &Req) {
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if (Req.Instances.empty())
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return llvm::createStringError(
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std::errc::invalid_argument,
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"TLASBuildRequest: Must have at least one instance.");
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for (size_t I = 0; I < Req.Instances.size(); ++I)
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if (!Req.Instances[I].BLAS)
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return llvm::createStringError(
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std::errc::invalid_argument,
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"TLASBuildRequest: Instance %zu has a null BLAS pointer.", I);
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return llvm::Error::success();
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}
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class AccelerationStructure {
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GPUAPI API;
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public:
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virtual ~AccelerationStructure();
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AccelerationStructure(const AccelerationStructure &) = delete;
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AccelerationStructure &operator=(const AccelerationStructure &) = delete;
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GPUAPI getAPI() const { return API; }
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protected:
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explicit AccelerationStructure(GPUAPI API) : API(API) {}
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};
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} // namespace offloadtest
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#endif // OFFLOADTEST_API_ACCELERATIONSTRUCTURE_H

‎include/API/Device.h‎

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#include "Config.h"
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#include "API/API.h"
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#include "API/AccelerationStructure.h"
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#include "API/Buffer.h"
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#include "API/Capabilities.h"
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#include "API/CommandBuffer.h"
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virtual llvm::Expected<std::unique_ptr<CommandBuffer>>
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createCommandBuffer() = 0;
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virtual llvm::Expected<BLASBuildRequest> createBLASBuildRequest(
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llvm::ArrayRef<TriangleGeometryDesc> Triangles,
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llvm::ArrayRef<AABBGeometryDesc> AABBs,
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AccelerationStructureBuildFlags Flags = BuildFlagNone) = 0;
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virtual llvm::Expected<TLASBuildRequest> createTLASBuildRequest(
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llvm::ArrayRef<AccelerationStructureInstance> Instances,
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AccelerationStructureBuildFlags Flags = BuildFlagNone) = 0;
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virtual llvm::Expected<std::unique_ptr<AccelerationStructure>>
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createAccelerationStructure(const BLASBuildRequest &Request) = 0;
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virtual llvm::Expected<std::unique_ptr<AccelerationStructure>>
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createAccelerationStructure(const TLASBuildRequest &Request) = 0;
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virtual ~Device() = 0;
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llvm::StringRef getDescription() const { return Description; }

‎lib/API/DX/DXResources.h‎

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return Flags;
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}
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inline DXGI_FORMAT getDXGIIndexFormat(IndexFormat Fmt) {
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switch (Fmt) {
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case IndexFormat::Uint16:
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return DXGI_FORMAT_R16_UINT;
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case IndexFormat::Uint32:
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return DXGI_FORMAT_R32_UINT;
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}
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llvm_unreachable("All IndexFormat cases handled");
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}
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} // namespace offloadtest
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#endif // OFFLOADTEST_API_DXRESOURCES_H

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