diff options
-rw-r--r-- | llvm/include/llvm/InitializePasses.h | 1 | ||||
-rw-r--r-- | llvm/include/llvm/Transforms/IPO.h | 6 | ||||
-rw-r--r-- | llvm/include/llvm/Transforms/IPO/PassManagerBuilder.h | 1 | ||||
-rw-r--r-- | llvm/lib/Transforms/IPO/CMakeLists.txt | 1 | ||||
-rw-r--r-- | llvm/lib/Transforms/IPO/ElimAvailExtern.cpp | 96 | ||||
-rw-r--r-- | llvm/lib/Transforms/IPO/PassManagerBuilder.cpp | 12 |
6 files changed, 117 insertions, 0 deletions
diff --git a/llvm/include/llvm/InitializePasses.h b/llvm/include/llvm/InitializePasses.h index 4f95c886800..f6b497dc78c 100644 --- a/llvm/include/llvm/InitializePasses.h +++ b/llvm/include/llvm/InitializePasses.h @@ -130,6 +130,7 @@ void initializeSanitizerCoverageModulePass(PassRegistry&); void initializeDataFlowSanitizerPass(PassRegistry&); void initializeScalarizerPass(PassRegistry&); void initializeEarlyCSELegacyPassPass(PassRegistry &); +void initializeEliminateAvailableExternallyPass(PassRegistry&); void initializeExpandISelPseudosPass(PassRegistry&); void initializeFunctionAttrsPass(PassRegistry&); void initializeGCMachineCodeAnalysisPass(PassRegistry&); diff --git a/llvm/include/llvm/Transforms/IPO.h b/llvm/include/llvm/Transforms/IPO.h index fbd999cbc94..2ea47301bb4 100644 --- a/llvm/include/llvm/Transforms/IPO.h +++ b/llvm/include/llvm/Transforms/IPO.h @@ -71,6 +71,12 @@ ModulePass *createGlobalOptimizerPass(); ModulePass *createGlobalDCEPass(); //===----------------------------------------------------------------------===// +/// This transform is designed to eliminate available external globals +/// (functions or global variables) +/// +ModulePass *createEliminateAvailableExternallyPass(); + +//===----------------------------------------------------------------------===// /// createGVExtractionPass - If deleteFn is true, this pass deletes /// the specified global values. Otherwise, it deletes as much of the module as /// possible, except for the global values specified. diff --git a/llvm/include/llvm/Transforms/IPO/PassManagerBuilder.h b/llvm/include/llvm/Transforms/IPO/PassManagerBuilder.h index 5d574ae0bf0..1334dd0da23 100644 --- a/llvm/include/llvm/Transforms/IPO/PassManagerBuilder.h +++ b/llvm/include/llvm/Transforms/IPO/PassManagerBuilder.h @@ -121,6 +121,7 @@ public: bool VerifyInput; bool VerifyOutput; bool MergeFunctions; + bool PrepareForLTO; private: /// ExtensionList - This is list of all of the extensions that are registered. diff --git a/llvm/lib/Transforms/IPO/CMakeLists.txt b/llvm/lib/Transforms/IPO/CMakeLists.txt index 3df17b920a9..336dac45e13 100644 --- a/llvm/lib/Transforms/IPO/CMakeLists.txt +++ b/llvm/lib/Transforms/IPO/CMakeLists.txt @@ -3,6 +3,7 @@ add_llvm_library(LLVMipo BarrierNoopPass.cpp ConstantMerge.cpp DeadArgumentElimination.cpp + ElimAvailExtern.cpp ExtractGV.cpp FunctionAttrs.cpp GlobalDCE.cpp diff --git a/llvm/lib/Transforms/IPO/ElimAvailExtern.cpp b/llvm/lib/Transforms/IPO/ElimAvailExtern.cpp new file mode 100644 index 00000000000..e70ab871b88 --- /dev/null +++ b/llvm/lib/Transforms/IPO/ElimAvailExtern.cpp @@ -0,0 +1,96 @@ +//===-- ElimAvailExtern.cpp - DCE unreachable internal functions ----------------===// +// +// The LLVM Compiler Infrastructure +// +// This file is distributed under the University of Illinois Open Source +// License. See LICENSE.TXT for details. +// +//===----------------------------------------------------------------------===// +// +// This transform is designed to eliminate available external global +// definitions from the program, turning them into declarations. +// +//===----------------------------------------------------------------------===// + +#include "llvm/Transforms/IPO.h" +#include "llvm/ADT/Statistic.h" +#include "llvm/IR/Constants.h" +#include "llvm/IR/Instructions.h" +#include "llvm/IR/Module.h" +#include "llvm/Transforms/Utils/CtorUtils.h" +#include "llvm/Transforms/Utils/GlobalStatus.h" +#include "llvm/Pass.h" +using namespace llvm; + +#define DEBUG_TYPE "elim-avail-extern" + +STATISTIC(NumAliases , "Number of global aliases removed"); +STATISTIC(NumFunctions, "Number of functions removed"); +STATISTIC(NumVariables, "Number of global variables removed"); + +namespace { + struct EliminateAvailableExternally : public ModulePass { + static char ID; // Pass identification, replacement for typeid + EliminateAvailableExternally() : ModulePass(ID) { + initializeEliminateAvailableExternallyPass( + *PassRegistry::getPassRegistry()); + } + + // run - Do the EliminateAvailableExternally pass on the specified module, + // optionally updating the specified callgraph to reflect the changes. + // + bool runOnModule(Module &M) override; + }; +} + +char EliminateAvailableExternally::ID = 0; +INITIALIZE_PASS(EliminateAvailableExternally, "elim-avail-extern", + "Eliminate Available Externally Globals", false, false) + +ModulePass *llvm::createEliminateAvailableExternallyPass() { + return new EliminateAvailableExternally(); +} + +bool EliminateAvailableExternally::runOnModule(Module &M) { + bool Changed = false; + + // Drop initializers of available externally global variables. + for (Module::global_iterator I = M.global_begin(), E = M.global_end(); + I != E; ++I) { + if (!I->hasAvailableExternallyLinkage()) + continue; + if (I->hasInitializer()) { + Constant *Init = I->getInitializer(); + I->setInitializer(nullptr); + if (isSafeToDestroyConstant(Init)) + Init->destroyConstant(); + } + I->removeDeadConstantUsers(); + I->setLinkage(GlobalValue::ExternalLinkage); + NumVariables++; + } + + // Drop the bodies of available externally functions. + for (Module::iterator I = M.begin(), E = M.end(); I != E; ++I) { + if (!I->hasAvailableExternallyLinkage()) + continue; + if (!I->isDeclaration()) + // This will set the linkage to external + I->deleteBody(); + I->removeDeadConstantUsers(); + NumFunctions++; + } + + // Drop targets of available externally aliases. + for (Module::alias_iterator I = M.alias_begin(), E = M.alias_end(); I != E; + ++I) { + if (!I->hasAvailableExternallyLinkage()) + continue; + I->setAliasee(nullptr); + I->removeDeadConstantUsers(); + I->setLinkage(GlobalValue::ExternalLinkage); + NumAliases++; + } + + return Changed; +} diff --git a/llvm/lib/Transforms/IPO/PassManagerBuilder.cpp b/llvm/lib/Transforms/IPO/PassManagerBuilder.cpp index 963f1bb13aa..a067a4b4525 100644 --- a/llvm/lib/Transforms/IPO/PassManagerBuilder.cpp +++ b/llvm/lib/Transforms/IPO/PassManagerBuilder.cpp @@ -105,6 +105,7 @@ PassManagerBuilder::PassManagerBuilder() { VerifyInput = false; VerifyOutput = false; MergeFunctions = false; + PrepareForLTO = false; } PassManagerBuilder::~PassManagerBuilder() { @@ -401,6 +402,17 @@ void PassManagerBuilder::populateModulePassManager( // GlobalOpt already deletes dead functions and globals, at -O2 try a // late pass of GlobalDCE. It is capable of deleting dead cycles. if (OptLevel > 1) { + if (!PrepareForLTO) { + // Remove avail extern fns and globals definitions if we aren't + // compiling an object file for later LTO. For LTO we want to preserve + // these so they are eligible for inlining at link-time. Note if they + // are unreferenced they will be removed by GlobalDCE below, so + // this only impacts referenced available externally globals. + // Eventually they will be suppressed during codegen, but eliminating + // here enables more opportunity for GlobalDCE as it may make + // globals referenced by available external functions dead. + MPM.add(createEliminateAvailableExternallyPass()); + } MPM.add(createGlobalDCEPass()); // Remove dead fns and globals. MPM.add(createConstantMergePass()); // Merge dup global constants } |