00ad9ecc1c
This patch introduces a new pass, SPIRVCBufferAccess, which is responsible for translating accesses to HLSL constant buffer (cbuffer) global variables into accesses to the proper SPIR-V resource. The pass operates by: 1. Identifying all cbuffers via the `!hlsl.cbs` metadata. 2. Replacing all uses of cbuffer member global variables with `llvm.spv.resource.getpointer` intrinsics. 3. Cleaning up the original global variables and metadata. This approach allows subsequent passes, like SPIRVEmitIntrinsics, to correctly fold GEPs into a single OpAccessChain instruction. The patch also includes a comprehensive set of lit tests to cover various scenarios: - Basic cbuffer access direct load and GEPs. - Unused and partially unused cbuffers. This implements the SPIR-V version of https://github.com/llvm/wg-hlsl/blob/main/proposals/0016-constant-buffers.md#lowering-to-buffer-load-intrinsics.
74 lines
2.5 KiB
C++
74 lines
2.5 KiB
C++
//===- CBuffer.cpp - HLSL constant buffer handling ------------------------===//
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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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#include "llvm/Frontend/HLSL/CBuffer.h"
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#include "llvm/Frontend/HLSL/HLSLResource.h"
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#include "llvm/IR/DerivedTypes.h"
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#include "llvm/IR/Metadata.h"
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#include "llvm/IR/Module.h"
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using namespace llvm;
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using namespace llvm::hlsl;
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static size_t getMemberOffset(GlobalVariable *Handle, size_t Index) {
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auto *HandleTy = cast<TargetExtType>(Handle->getValueType());
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assert((HandleTy->getName().ends_with(".CBuffer") ||
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HandleTy->getName() == "spirv.VulkanBuffer") &&
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"Not a cbuffer type");
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assert(HandleTy->getNumTypeParameters() == 1 && "Expected layout type");
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auto *LayoutTy = cast<TargetExtType>(HandleTy->getTypeParameter(0));
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assert(LayoutTy->getName().ends_with(".Layout") && "Not a layout type");
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// Skip the "size" parameter.
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size_t ParamIndex = Index + 1;
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assert(LayoutTy->getNumIntParameters() > ParamIndex &&
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"Not enough parameters");
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return LayoutTy->getIntParameter(ParamIndex);
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}
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std::optional<CBufferMetadata> CBufferMetadata::get(Module &M) {
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NamedMDNode *CBufMD = M.getNamedMetadata("hlsl.cbs");
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if (!CBufMD)
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return std::nullopt;
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std::optional<CBufferMetadata> Result({CBufMD});
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for (const MDNode *MD : CBufMD->operands()) {
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assert(MD->getNumOperands() && "Invalid cbuffer metadata");
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auto *Handle = cast<GlobalVariable>(
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cast<ValueAsMetadata>(MD->getOperand(0))->getValue());
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CBufferMapping &Mapping = Result->Mappings.emplace_back(Handle);
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for (int I = 1, E = MD->getNumOperands(); I < E; ++I) {
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Metadata *OpMD = MD->getOperand(I);
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// Some members may be null if they've been optimized out.
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if (!OpMD)
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continue;
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auto *V = cast<GlobalVariable>(cast<ValueAsMetadata>(OpMD)->getValue());
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Mapping.Members.emplace_back(V, getMemberOffset(Handle, I - 1));
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}
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}
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return Result;
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}
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void CBufferMetadata::eraseFromModule() {
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// Remove the cbs named metadata
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MD->eraseFromParent();
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}
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APInt hlsl::translateCBufArrayOffset(const DataLayout &DL, APInt Offset,
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ArrayType *Ty) {
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int64_t TypeSize = DL.getTypeSizeInBits(Ty->getElementType()) / 8;
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int64_t RoundUp = alignTo(TypeSize, Align(CBufferRowSizeInBytes));
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return Offset.udiv(TypeSize) * RoundUp;
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}
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