//===- NameAnonGlobals.cpp - ThinLTO Support: Name Unnamed Globals --------===//
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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 file implements naming anonymous globals to make sure they can be
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// referred to by ThinLTO.
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//
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//===----------------------------------------------------------------------===//
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#include "llvm/Transforms/Utils/NameAnonGlobals.h"
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#include "llvm/ADT/SmallString.h"
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#include "llvm/IR/Module.h"
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#include "llvm/Support/MD5.h"
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#include "llvm/Transforms/Utils/ModuleUtils.h"
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using namespace llvm;
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namespace {
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// Compute a "unique" hash for the module based on the name of the public
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// globals.
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class ModuleHasher {
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Module &TheModule;
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std::string TheHash;
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public:
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ModuleHasher(Module &M) : TheModule(M) {}
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/// Return the lazily computed hash.
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std::string &get() {
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if (!TheHash.empty())
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// Cache hit :)
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return TheHash;
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MD5 Hasher;
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for (auto &F : TheModule) {
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if (F.isDeclaration() || F.hasLocalLinkage() || !F.hasName())
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continue;
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auto Name = F.getName();
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Hasher.update(Name);
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}
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for (auto &GV : TheModule.globals()) {
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if (GV.isDeclaration() || GV.hasLocalLinkage() || !GV.hasName())
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continue;
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auto Name = GV.getName();
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Hasher.update(Name);
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}
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// Now return the result.
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MD5::MD5Result Hash;
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Hasher.final(Hash);
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SmallString<32> Result;
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MD5::stringifyResult(Hash, Result);
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TheHash = Result.str();
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return TheHash;
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}
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};
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} // end anonymous namespace
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// Rename all the anon globals in the module
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bool llvm::nameUnamedGlobals(Module &M) {
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bool Changed = false;
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ModuleHasher ModuleHash(M);
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int count = 0;
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auto RenameIfNeed = [&](GlobalValue &GV) {
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if (GV.hasName())
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return;
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GV.setName(Twine("anon.") + ModuleHash.get() + "." + Twine(count++));
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Changed = true;
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};
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for (auto &GO : M.global_objects())
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RenameIfNeed(GO);
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for (auto &GA : M.aliases())
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RenameIfNeed(GA);
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return Changed;
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}
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namespace {
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// Legacy pass that provides a name to every anon globals.
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class NameAnonGlobalLegacyPass : public ModulePass {
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public:
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/// Pass identification, replacement for typeid
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static char ID;
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/// Specify pass name for debug output
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StringRef getPassName() const override { return "Name Anon Globals"; }
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explicit NameAnonGlobalLegacyPass() : ModulePass(ID) {}
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bool runOnModule(Module &M) override { return nameUnamedGlobals(M); }
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};
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char NameAnonGlobalLegacyPass::ID = 0;
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} // anonymous namespace
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PreservedAnalyses NameAnonGlobalPass::run(Module &M,
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ModuleAnalysisManager &AM) {
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if (!nameUnamedGlobals(M))
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return PreservedAnalyses::all();
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return PreservedAnalyses::none();
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}
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INITIALIZE_PASS_BEGIN(NameAnonGlobalLegacyPass, "name-anon-globals",
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"Provide a name to nameless globals", false, false)
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INITIALIZE_PASS_END(NameAnonGlobalLegacyPass, "name-anon-globals",
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"Provide a name to nameless globals", false, false)
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namespace llvm {
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ModulePass *createNameAnonGlobalPass() {
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return new NameAnonGlobalLegacyPass();
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}
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}
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