forked from OSchip/llvm-project
86 lines
2.7 KiB
C++
86 lines
2.7 KiB
C++
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//===- SplitModule.cpp - Split a module into partitions -------------------===//
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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 defines the function llvm::SplitModule, which splits a module
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// into multiple linkable partitions. It can be used to implement parallel code
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// generation for link-time optimization.
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//
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//===----------------------------------------------------------------------===//
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#include "llvm/Transforms/Utils/SplitModule.h"
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#include "llvm/ADT/Hashing.h"
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#include "llvm/IR/Function.h"
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#include "llvm/IR/GlobalAlias.h"
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#include "llvm/IR/GlobalObject.h"
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#include "llvm/IR/GlobalValue.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/Support/raw_ostream.h"
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#include "llvm/Transforms/Utils/Cloning.h"
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using namespace llvm;
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static void externalize(GlobalValue *GV) {
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if (GV->hasLocalLinkage()) {
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GV->setLinkage(GlobalValue::ExternalLinkage);
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GV->setVisibility(GlobalValue::HiddenVisibility);
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}
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// Unnamed entities must be named consistently between modules. setName will
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// give a distinct name to each such entity.
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if (!GV->hasName())
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GV->setName("__llvmsplit_unnamed");
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}
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// Returns whether GV should be in partition (0-based) I of N.
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static bool isInPartition(const GlobalValue *GV, unsigned I, unsigned N) {
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if (auto GA = dyn_cast<GlobalAlias>(GV))
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if (const GlobalObject *Base = GA->getBaseObject())
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GV = Base;
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StringRef Name;
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if (const Comdat *C = GV->getComdat())
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Name = C->getName();
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else
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Name = GV->getName();
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// Partition by MD5 hash. We only need a few bits for evenness as the number
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// of partitions will generally be in the 1-2 figure range; the low 16 bits
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// are enough.
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MD5 H;
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MD5::MD5Result R;
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H.update(Name);
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H.final(R);
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return (R[0] | (R[1] << 8)) % N == I;
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}
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void llvm::SplitModule(
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std::unique_ptr<Module> M, unsigned N,
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std::function<void(std::unique_ptr<Module> MPart)> ModuleCallback) {
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for (Function &F : *M)
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externalize(&F);
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for (GlobalVariable &GV : M->globals())
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externalize(&GV);
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for (GlobalAlias &GA : M->aliases())
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externalize(&GA);
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// FIXME: We should be able to reuse M as the last partition instead of
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// cloning it.
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for (unsigned I = 0; I != N; ++I) {
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ValueToValueMapTy VMap;
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std::unique_ptr<Module> MPart(
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CloneModule(M.get(), VMap, [=](const GlobalValue *GV) {
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return isInPartition(GV, I, N);
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}));
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if (I != 0)
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MPart->setModuleInlineAsm("");
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ModuleCallback(std::move(MPart));
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}
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}
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