1 //===- Utility.cpp ------ Collection of generic offloading utilities ------===//
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/Offloading/Utility.h"
10 #include "llvm/IR/Constants.h"
11 #include "llvm/IR/GlobalValue.h"
12 #include "llvm/IR/GlobalVariable.h"
13 #include "llvm/IR/Value.h"
14 #include "llvm/Transforms/Utils/ModuleUtils.h"
15
16 using namespace llvm;
17 using namespace llvm::offloading;
18
getEntryTy(Module & M)19 StructType *offloading::getEntryTy(Module &M) {
20 LLVMContext &C = M.getContext();
21 StructType *EntryTy =
22 StructType::getTypeByName(C, "struct.__tgt_offload_entry");
23 if (!EntryTy)
24 EntryTy = StructType::create(
25 "struct.__tgt_offload_entry", PointerType::getUnqual(C),
26 PointerType::getUnqual(C), M.getDataLayout().getIntPtrType(C),
27 Type::getInt32Ty(C), Type::getInt32Ty(C));
28 return EntryTy;
29 }
30
31 // TODO: Rework this interface to be more generic.
32 std::pair<Constant *, GlobalVariable *>
getOffloadingEntryInitializer(Module & M,Constant * Addr,StringRef Name,uint64_t Size,int32_t Flags,int32_t Data)33 offloading::getOffloadingEntryInitializer(Module &M, Constant *Addr,
34 StringRef Name, uint64_t Size,
35 int32_t Flags, int32_t Data) {
36 llvm::Triple Triple(M.getTargetTriple());
37 Type *Int8PtrTy = PointerType::getUnqual(M.getContext());
38 Type *Int32Ty = Type::getInt32Ty(M.getContext());
39 Type *SizeTy = M.getDataLayout().getIntPtrType(M.getContext());
40
41 Constant *AddrName = ConstantDataArray::getString(M.getContext(), Name);
42
43 StringRef Prefix =
44 Triple.isNVPTX() ? "$offloading$entry_name" : ".offloading.entry_name";
45
46 // Create the constant string used to look up the symbol in the device.
47 auto *Str =
48 new GlobalVariable(M, AddrName->getType(), /*isConstant=*/true,
49 GlobalValue::InternalLinkage, AddrName, Prefix);
50 Str->setUnnamedAddr(GlobalValue::UnnamedAddr::Global);
51
52 // Construct the offloading entry.
53 Constant *EntryData[] = {
54 ConstantExpr::getPointerBitCastOrAddrSpaceCast(Addr, Int8PtrTy),
55 ConstantExpr::getPointerBitCastOrAddrSpaceCast(Str, Int8PtrTy),
56 ConstantInt::get(SizeTy, Size),
57 ConstantInt::get(Int32Ty, Flags),
58 ConstantInt::get(Int32Ty, Data),
59 };
60 Constant *EntryInitializer = ConstantStruct::get(getEntryTy(M), EntryData);
61 return {EntryInitializer, Str};
62 }
63
emitOffloadingEntry(Module & M,Constant * Addr,StringRef Name,uint64_t Size,int32_t Flags,int32_t Data,StringRef SectionName)64 void offloading::emitOffloadingEntry(Module &M, Constant *Addr, StringRef Name,
65 uint64_t Size, int32_t Flags, int32_t Data,
66 StringRef SectionName) {
67 llvm::Triple Triple(M.getTargetTriple());
68
69 auto [EntryInitializer, NameGV] =
70 getOffloadingEntryInitializer(M, Addr, Name, Size, Flags, Data);
71
72 StringRef Prefix =
73 Triple.isNVPTX() ? "$offloading$entry$" : ".offloading.entry.";
74 auto *Entry = new GlobalVariable(
75 M, getEntryTy(M),
76 /*isConstant=*/true, GlobalValue::WeakAnyLinkage, EntryInitializer,
77 Prefix + Name, nullptr, GlobalValue::NotThreadLocal,
78 M.getDataLayout().getDefaultGlobalsAddressSpace());
79
80 // The entry has to be created in the section the linker expects it to be.
81 if (Triple.isOSBinFormatCOFF())
82 Entry->setSection((SectionName + "$OE").str());
83 else
84 Entry->setSection(SectionName);
85 Entry->setAlignment(Align(1));
86 }
87
88 std::pair<GlobalVariable *, GlobalVariable *>
getOffloadEntryArray(Module & M,StringRef SectionName)89 offloading::getOffloadEntryArray(Module &M, StringRef SectionName) {
90 llvm::Triple Triple(M.getTargetTriple());
91
92 auto *ZeroInitilaizer =
93 ConstantAggregateZero::get(ArrayType::get(getEntryTy(M), 0u));
94 auto *EntryInit = Triple.isOSBinFormatCOFF() ? ZeroInitilaizer : nullptr;
95 auto *EntryType = ArrayType::get(getEntryTy(M), 0);
96 auto Linkage = Triple.isOSBinFormatCOFF() ? GlobalValue::WeakODRLinkage
97 : GlobalValue::ExternalLinkage;
98
99 auto *EntriesB =
100 new GlobalVariable(M, EntryType, /*isConstant=*/true, Linkage, EntryInit,
101 "__start_" + SectionName);
102 EntriesB->setVisibility(GlobalValue::HiddenVisibility);
103 auto *EntriesE =
104 new GlobalVariable(M, EntryType, /*isConstant=*/true, Linkage, EntryInit,
105 "__stop_" + SectionName);
106 EntriesE->setVisibility(GlobalValue::HiddenVisibility);
107
108 if (Triple.isOSBinFormatELF()) {
109 // We assume that external begin/end symbols that we have created above will
110 // be defined by the linker. This is done whenever a section name with a
111 // valid C-identifier is present. We define a dummy variable here to force
112 // the linker to always provide these symbols.
113 auto *DummyEntry = new GlobalVariable(
114 M, ZeroInitilaizer->getType(), true, GlobalVariable::InternalLinkage,
115 ZeroInitilaizer, "__dummy." + SectionName);
116 DummyEntry->setSection(SectionName);
117 appendToCompilerUsed(M, DummyEntry);
118 } else {
119 // The COFF linker will merge sections containing a '$' together into a
120 // single section. The order of entries in this section will be sorted
121 // alphabetically by the characters following the '$' in the name. Set the
122 // sections here to ensure that the beginning and end symbols are sorted.
123 EntriesB->setSection((SectionName + "$OA").str());
124 EntriesE->setSection((SectionName + "$OZ").str());
125 }
126
127 return std::make_pair(EntriesB, EntriesE);
128 }
129