1//===- CBuffer.cpp - HLSL constant buffer handling ------------------------===//
2//
3// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
4// See https://llvm.org/LICENSE.txt for license information.
5// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
6//
7//===----------------------------------------------------------------------===//
8
9#include "llvm/Frontend/HLSL/CBuffer.h"
10#include "llvm/Frontend/HLSL/HLSLResource.h"
11#include "llvm/IR/DerivedTypes.h"
12#include "llvm/IR/Metadata.h"
13#include "llvm/IR/Module.h"
14
15using namespace llvm;
16using namespace llvm::hlsl;
17
18static SmallVector<size_t>
19getMemberOffsets(const DataLayout &DL, GlobalVariable *Handle,
20 llvm::function_ref<bool(Type *)> IsPadding) {
21 SmallVector<size_t> Offsets;
22
23 auto *HandleTy = cast<TargetExtType>(Val: Handle->getValueType());
24 assert((HandleTy->getName().ends_with(".CBuffer") ||
25 HandleTy->getName() == "spirv.VulkanBuffer") &&
26 "Not a cbuffer type");
27 assert(HandleTy->getNumTypeParameters() == 1 && "Expected layout type");
28 auto *LayoutTy = cast<StructType>(Val: HandleTy->getTypeParameter(i: 0));
29
30 const StructLayout *SL = DL.getStructLayout(Ty: LayoutTy);
31 for (int I = 0, E = LayoutTy->getNumElements(); I < E; ++I)
32 if (!IsPadding(LayoutTy->getElementType(N: I)))
33 Offsets.push_back(Elt: SL->getElementOffset(Idx: I));
34
35 return Offsets;
36}
37
38std::optional<CBufferMetadata>
39CBufferMetadata::get(Module &M, llvm::function_ref<bool(Type *)> IsPadding) {
40 NamedMDNode *CBufMD = M.getNamedMetadata(Name: "hlsl.cbs");
41 if (!CBufMD)
42 return std::nullopt;
43
44 std::optional<CBufferMetadata> Result({CBufMD});
45
46 for (const MDNode *MD : CBufMD->operands()) {
47 assert(MD->getNumOperands() && "Invalid cbuffer metadata");
48
49 // For an unused cbuffer, the handle may have been optimized out
50 Metadata *OpMD = MD->getOperand(I: 0);
51 if (!OpMD)
52 continue;
53
54 auto *Handle =
55 cast<GlobalVariable>(Val: cast<ValueAsMetadata>(Val: OpMD)->getValue());
56 CBufferMapping &Mapping = Result->Mappings.emplace_back(Args&: Handle);
57
58 SmallVector<size_t> MemberOffsets =
59 getMemberOffsets(DL: M.getDataLayout(), Handle, IsPadding);
60
61 for (int I = 1, E = MD->getNumOperands(); I < E; ++I) {
62 Metadata *OpMD = MD->getOperand(I);
63 // Some members may be null if they've been optimized out.
64 if (!OpMD)
65 continue;
66 auto *V = cast<GlobalVariable>(Val: cast<ValueAsMetadata>(Val: OpMD)->getValue());
67 Mapping.Members.emplace_back(Args&: V, Args&: MemberOffsets[I - 1]);
68 }
69 }
70
71 return Result;
72}
73
74void CBufferMetadata::eraseFromModule() {
75 // Remove the cbs named metadata
76 MD->eraseFromParent();
77}
78