lib/Transforms/IPO/ExtractGV.cpp

   1 //===-- ExtractGV.cpp - Global Value extraction pass ----------------------===//
   2 //
   3 //                     The LLVM Compiler Infrastructure
   4 //
   5 // This file is distributed under the University of Illinois Open Source
   6 // License. See LICENSE.TXT for details.
   7 //
   8 //===----------------------------------------------------------------------===//
   9 //
  10 // This pass extracts global values
  11 //
  12 //===----------------------------------------------------------------------===//
  13
  14 #include "llvm/Instructions.h"
  15 #include "llvm/LLVMContext.h"
  16 #include "llvm/Module.h"
  17 #include "llvm/Pass.h"
  18 #include "llvm/Constants.h"
  19 #include "llvm/Transforms/IPO.h"
  20 #include "llvm/ADT/SetVector.h"
  21 #include <algorithm>
  22 using namespace llvm;
  23
  24 namespace {
  25   /// @brief A pass to extract specific functions and their dependencies.
  26   class GVExtractorPass : public ModulePass {
  27     SetVector<GlobalValue *> Named;
  28     bool deleteStuff;
  29   public:
  30     static char ID; // Pass identification, replacement for typeid
  31
  32     /// FunctionExtractorPass - If deleteFn is true, this pass deletes as the
  33     /// specified function. Otherwise, it deletes as much of the module as
  34     /// possible, except for the function specified.
  35     ///
  36     explicit GVExtractorPass(std::vector<GlobalValue*>& GVs, bool deleteS = true)
  37       : ModulePass(ID), Named(GVs.begin(), GVs.end()), deleteStuff(deleteS) {}
  38
  39     bool runOnModule(Module &M) {
  40       // Visit the global inline asm.
  41       if (!deleteStuff)
  42         M.setModuleInlineAsm("");
  43
  44       // For simplicity, just give all GlobalValues ExternalLinkage. A trickier
  45       // implementation could figure out which GlobalValues are actually
  46       // referenced by the Named set, and which GlobalValues in the rest of
  47       // the module are referenced by the NamedSet, and get away with leaving
  48       // more internal and private things internal and private. But for now,
  49       // be conservative and simple.
  50
  51       // Visit the GlobalVariables.
  52       for (Module::global_iterator I = M.global_begin(), E = M.global_end();
  53            I != E; ++I) {
  54         if (deleteStuff == (bool)Named.count(I) && !I->isDeclaration()) {
  55           I->setInitializer(0);
  56         } else {
  57           if (I->hasAvailableExternallyLinkage())
  58             continue;
  59           if (I->getName() == "llvm.global_ctors")
  60             continue;
  61         }
  62
  63         if (I->hasLocalLinkage())
  64           I->setVisibility(GlobalValue::HiddenVisibility);
  65         I->setLinkage(GlobalValue::ExternalLinkage);
  66       }
  67
  68       // Visit the Functions.
  69       for (Module::iterator I = M.begin(), E = M.end(); I != E; ++I) {
  70         if (deleteStuff == (bool)Named.count(I) && !I->isDeclaration()) {
  71           I->deleteBody();
  72         } else {
  73           if (I->hasAvailableExternallyLinkage())
  74             continue;
  75         }
  76
  77         if (I->hasLocalLinkage())
  78           I->setVisibility(GlobalValue::HiddenVisibility);
  79         I->setLinkage(GlobalValue::ExternalLinkage);
  80       }
  81
  82       return true;
  83     }
  84   };
  85
  86   char GVExtractorPass::ID = 0;
  87 }
  88
  89 ModulePass *llvm::createGVExtractionPass(std::vector<GlobalValue*>& GVs,
  90                                          bool deleteFn) {
  91   return new GVExtractorPass(GVs, deleteFn);
  92 }