52204a29ab
Summary: This patch provides the initial support to allow handling the new driver's offloading entries. Normally, the ELF target can emit varibles at C-identifier named sections and the linker will provide a pointer to the section. For COFF target, instead the linker merges sections containing a `$` in alphabetical order. We thus can emit these variables at sections and then emit two variables that are guaranteed to be sorted before and after the others to traverse it. Previous patches consolidated the handling of offloading entries so that this patch more easily can handle mapping them to the appropriate section. Ideally, the only remaining step to allow the new driver to run on Windows targets is to accurately map the following `ld.lld` arguments to their `llvm-link` equivalents. These are used inside the linker-wrapper, so we should simply need to remap the arguments to the same functionality if possible. ``` -o, -output -l, --library -L, --library-path -v, --version -rpath -whole-archive, -no-whole-archive ``` I have not tested this at runtime as I do not have access to a windows machine. This patch was adapted from some initial efforts in https://reviews.llvm.org/D137470.
111 lines
4.8 KiB
C++
111 lines
4.8 KiB
C++
//===- Utility.cpp ------ Collection of geneirc offloading utilities ------===//
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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/Offloading/Utility.h"
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#include "llvm/IR/Constants.h"
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#include "llvm/IR/GlobalValue.h"
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#include "llvm/IR/GlobalVariable.h"
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#include "llvm/IR/Value.h"
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using namespace llvm;
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using namespace llvm::offloading;
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StructType *offloading::getEntryTy(Module &M) {
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LLVMContext &C = M.getContext();
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StructType *EntryTy =
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StructType::getTypeByName(C, "struct.__tgt_offload_entry");
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if (!EntryTy)
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EntryTy = StructType::create(
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"struct.__tgt_offload_entry", PointerType::getUnqual(C),
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PointerType::getUnqual(C), M.getDataLayout().getIntPtrType(C),
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Type::getInt32Ty(C), Type::getInt32Ty(C));
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return EntryTy;
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}
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// TODO: Rework this interface to be more generic.
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void offloading::emitOffloadingEntry(Module &M, Constant *Addr, StringRef Name,
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uint64_t Size, int32_t Flags,
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StringRef SectionName) {
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llvm::Triple Triple(M.getTargetTriple());
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Type *Int8PtrTy = PointerType::getUnqual(M.getContext());
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Type *Int32Ty = Type::getInt32Ty(M.getContext());
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Type *SizeTy = M.getDataLayout().getIntPtrType(M.getContext());
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Constant *AddrName = ConstantDataArray::getString(M.getContext(), Name);
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// Create the constant string used to look up the symbol in the device.
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auto *Str = new GlobalVariable(M, AddrName->getType(), /*isConstant=*/true,
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GlobalValue::InternalLinkage, AddrName,
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".omp_offloading.entry_name");
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Str->setUnnamedAddr(GlobalValue::UnnamedAddr::Global);
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// Construct the offloading entry.
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Constant *EntryData[] = {
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ConstantExpr::getPointerBitCastOrAddrSpaceCast(Addr, Int8PtrTy),
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ConstantExpr::getPointerBitCastOrAddrSpaceCast(Str, Int8PtrTy),
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ConstantInt::get(SizeTy, Size),
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ConstantInt::get(Int32Ty, Flags),
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ConstantInt::get(Int32Ty, 0),
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};
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Constant *EntryInitializer = ConstantStruct::get(getEntryTy(M), EntryData);
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auto *Entry = new GlobalVariable(
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M, getEntryTy(M),
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/*isConstant=*/true, GlobalValue::WeakAnyLinkage, EntryInitializer,
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".omp_offloading.entry." + Name, nullptr, GlobalValue::NotThreadLocal,
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M.getDataLayout().getDefaultGlobalsAddressSpace());
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// The entry has to be created in the section the linker expects it to be.
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if (Triple.isOSBinFormatCOFF())
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Entry->setSection((SectionName + "$OE").str());
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else
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Entry->setSection(SectionName);
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Entry->setAlignment(Align(1));
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}
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std::pair<GlobalVariable *, GlobalVariable *>
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offloading::getOffloadEntryArray(Module &M, StringRef SectionName) {
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llvm::Triple Triple(M.getTargetTriple());
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auto *ZeroInitilaizer =
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ConstantAggregateZero::get(ArrayType::get(getEntryTy(M), 0u));
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auto *EntryInit = Triple.isOSBinFormatCOFF() ? ZeroInitilaizer : nullptr;
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auto *EntryType = ArrayType::get(getEntryTy(M), 0);
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auto *EntriesB = new GlobalVariable(M, EntryType, /*isConstant=*/true,
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GlobalValue::ExternalLinkage, EntryInit,
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"__start_" + SectionName);
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EntriesB->setVisibility(GlobalValue::HiddenVisibility);
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auto *EntriesE = new GlobalVariable(M, EntryType, /*isConstant=*/true,
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GlobalValue::ExternalLinkage, EntryInit,
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"__stop_" + SectionName);
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EntriesE->setVisibility(GlobalValue::HiddenVisibility);
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if (Triple.isOSBinFormatELF()) {
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// We assume that external begin/end symbols that we have created above will
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// be defined by the linker. This is done whenever a section name with a
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// valid C-identifier is present. We define a dummy variable here to force
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// the linker to always provide these symbols.
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auto *DummyEntry = new GlobalVariable(
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M, ZeroInitilaizer->getType(), true, GlobalVariable::ExternalLinkage,
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ZeroInitilaizer, "__dummy." + SectionName);
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DummyEntry->setSection(SectionName);
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DummyEntry->setVisibility(GlobalValue::HiddenVisibility);
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} else {
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// The COFF linker will merge sections containing a '$' together into a
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// single section. The order of entries in this section will be sorted
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// alphabetically by the characters following the '$' in the name. Set the
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// sections here to ensure that the beginning and end symbols are sorted.
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EntriesB->setSection((SectionName + "$OA").str());
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EntriesE->setSection((SectionName + "$OZ").str());
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}
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return std::make_pair(EntriesB, EntriesE);
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}
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