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4ef7eafa3f
The language reference says that: "If a symbol appears in the @llvm.used list, then the compiler, assembler, and linker are required to treat the symbol as if there is a reference to the symbol that it cannot see" Since even the linker cannot see the reference, we must assume that the reference can be using the symbol table. For example, a user can add __attribute__((used)) to a debug helper function like dump and use it from a debugger. git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@187103 91177308-0d34-0410-b5e6-96231b3b80d8
83 lines
2.9 KiB
C++
83 lines
2.9 KiB
C++
//===-- ModuleUtils.cpp - Functions to manipulate Modules -----------------===//
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//
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// The LLVM Compiler Infrastructure
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//
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// This file is distributed under the University of Illinois Open Source
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// License. See LICENSE.TXT for details.
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//
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//===----------------------------------------------------------------------===//
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//
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// This family of functions perform manipulations on Modules.
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//
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//===----------------------------------------------------------------------===//
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#include "llvm/Transforms/Utils/ModuleUtils.h"
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#include "llvm/ADT/SmallPtrSet.h"
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#include "llvm/IR/DerivedTypes.h"
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#include "llvm/IR/Function.h"
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#include "llvm/IR/IRBuilder.h"
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#include "llvm/IR/Module.h"
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using namespace llvm;
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static void appendToGlobalArray(const char *Array,
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Module &M, Function *F, int Priority) {
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IRBuilder<> IRB(M.getContext());
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FunctionType *FnTy = FunctionType::get(IRB.getVoidTy(), false);
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StructType *Ty = StructType::get(
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IRB.getInt32Ty(), PointerType::getUnqual(FnTy), NULL);
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Constant *RuntimeCtorInit = ConstantStruct::get(
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Ty, IRB.getInt32(Priority), F, NULL);
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// Get the current set of static global constructors and add the new ctor
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// to the list.
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SmallVector<Constant *, 16> CurrentCtors;
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if (GlobalVariable * GVCtor = M.getNamedGlobal(Array)) {
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if (Constant *Init = GVCtor->getInitializer()) {
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unsigned n = Init->getNumOperands();
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CurrentCtors.reserve(n + 1);
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for (unsigned i = 0; i != n; ++i)
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CurrentCtors.push_back(cast<Constant>(Init->getOperand(i)));
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}
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GVCtor->eraseFromParent();
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}
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CurrentCtors.push_back(RuntimeCtorInit);
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// Create a new initializer.
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ArrayType *AT = ArrayType::get(RuntimeCtorInit->getType(),
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CurrentCtors.size());
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Constant *NewInit = ConstantArray::get(AT, CurrentCtors);
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// Create the new global variable and replace all uses of
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// the old global variable with the new one.
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(void)new GlobalVariable(M, NewInit->getType(), false,
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GlobalValue::AppendingLinkage, NewInit, Array);
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}
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void llvm::appendToGlobalCtors(Module &M, Function *F, int Priority) {
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appendToGlobalArray("llvm.global_ctors", M, F, Priority);
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}
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void llvm::appendToGlobalDtors(Module &M, Function *F, int Priority) {
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appendToGlobalArray("llvm.global_dtors", M, F, Priority);
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}
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GlobalVariable *
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llvm::collectUsedGlobalVariables(Module &M, SmallPtrSet<GlobalValue *, 8> &Set,
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bool CompilerUsed) {
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const char *Name = CompilerUsed ? "llvm.compiler.used" : "llvm.used";
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GlobalVariable *GV = M.getGlobalVariable(Name);
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if (!GV || !GV->hasInitializer())
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return GV;
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const ConstantArray *Init = cast<ConstantArray>(GV->getInitializer());
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for (unsigned I = 0, E = Init->getNumOperands(); I != E; ++I) {
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Value *Op = Init->getOperand(I);
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GlobalValue *G = cast<GlobalValue>(Op->stripPointerCastsNoFollowAliases());
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Set.insert(G);
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}
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return GV;
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}
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