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//===- CBuffer.cpp - HLSL constant buffer handling ------------------------===//
//
// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
// See https://llvm.org/LICENSE.txt for license information.
// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
//
//===----------------------------------------------------------------------===//
#include "llvm/Frontend/HLSL/CBuffer.h"
#include "llvm/Frontend/HLSL/HLSLResource.h"
#include "llvm/IR/DerivedTypes.h"
#include "llvm/IR/Metadata.h"
#include "llvm/IR/Module.h"
using namespace llvm;
using namespace llvm::hlsl;
static SmallVector<size_t>
getMemberOffsets(const DataLayout &DL, GlobalVariable *Handle,
llvm::function_ref<bool(Type *)> IsPadding) {
SmallVector<size_t> Offsets;
auto *HandleTy = cast<TargetExtType>(Handle->getValueType());
assert((HandleTy->getName().ends_with(".CBuffer") ||
HandleTy->getName() == "spirv.VulkanBuffer") &&
"Not a cbuffer type");
assert(HandleTy->getNumTypeParameters() == 1 && "Expected layout type");
auto *LayoutTy = cast<StructType>(HandleTy->getTypeParameter(0));
const StructLayout *SL = DL.getStructLayout(LayoutTy);
for (int I = 0, E = LayoutTy->getNumElements(); I < E; ++I)
if (!IsPadding(LayoutTy->getElementType(I)))
Offsets.push_back(SL->getElementOffset(I));
return Offsets;
}
std::optional<CBufferMetadata>
CBufferMetadata::get(Module &M, llvm::function_ref<bool(Type *)> IsPadding) {
NamedMDNode *CBufMD = M.getNamedMetadata("hlsl.cbs");
if (!CBufMD)
return std::nullopt;
std::optional<CBufferMetadata> Result({CBufMD});
for (const MDNode *MD : CBufMD->operands()) {
assert(MD->getNumOperands() && "Invalid cbuffer metadata");
// For an unused cbuffer, the handle may have been optimized out
Metadata *OpMD = MD->getOperand(0);
if (!OpMD)
continue;
auto *Handle =
cast<GlobalVariable>(cast<ValueAsMetadata>(OpMD)->getValue());
CBufferMapping &Mapping = Result->Mappings.emplace_back(Handle);
SmallVector<size_t> MemberOffsets =
getMemberOffsets(M.getDataLayout(), Handle, IsPadding);
for (int I = 1, E = MD->getNumOperands(); I < E; ++I) {
Metadata *OpMD = MD->getOperand(I);
// Some members may be null if they've been optimized out.
if (!OpMD)
continue;
auto *V = cast<GlobalVariable>(cast<ValueAsMetadata>(OpMD)->getValue());
Mapping.Members.emplace_back(V, MemberOffsets[I - 1]);
}
}
return Result;
}
void CBufferMetadata::eraseFromModule() {
// Remove the cbs named metadata
MD->eraseFromParent();
}
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