ExtractFunction.cpp revision 7c0e022c5c4be4b11e199a53f73bbdd84e34aa80 
1//===- ExtractFunction.cpp - Extract a function from Program --------------===//
2//
3//                     The LLVM Compiler Infrastructure
4//
5// This file was developed by the LLVM research group and is distributed under
6// the University of Illinois Open Source License. See LICENSE.TXT for details.
7//
8//===----------------------------------------------------------------------===//
9//
10//
11// This file implements a method that extracts a function from program, cleans
12// it up, and returns it as a new module.
13//
14//===----------------------------------------------------------------------===//
15
16#include "BugDriver.h"
17#include "llvm/Constant.h"
18#include "llvm/Module.h"
19#include "llvm/PassManager.h"
20#include "llvm/Pass.h"
21#include "llvm/Type.h"
22#include "llvm/Analysis/Verifier.h"
23#include "llvm/Transforms/IPO.h"
24#include "llvm/Transforms/Scalar.h"
25#include "llvm/Transforms/Utils/Cloning.h"
26#include "Support/CommandLine.h"
27
28bool DisableSimplifyCFG = false;
29
30namespace {
31  cl::opt<bool>
32  NoADCE("disable-adce",
33         cl::desc("Do not use the -adce pass to reduce testcases"));
34  cl::opt<bool>
35  NoDCE ("disable-dce",
36         cl::desc("Do not use the -dce pass to reduce testcases"));
37  cl::opt<bool, true>
38  NoSCFG("disable-simplifycfg", cl::location(DisableSimplifyCFG),
39         cl::desc("Do not use the -simplifycfg pass to reduce testcases"));
40  cl::opt<bool>
41  NoFinalCleanup("disable-final-cleanup",
42                 cl::desc("Disable the final cleanup phase of narrowing"));
43}
44
45/// deleteInstructionFromProgram - This method clones the current Program and
46/// deletes the specified instruction from the cloned module.  It then runs a
47/// series of cleanup passes (ADCE and SimplifyCFG) to eliminate any code which
48/// depends on the value.  The modified module is then returned.
49///
50Module *BugDriver::deleteInstructionFromProgram(Instruction *I,
51                                                unsigned Simplification) const {
52  Module *Result = CloneModule(Program);
53
54  BasicBlock *PBB = I->getParent();
55  Function *PF = PBB->getParent();
56
57  Module::iterator RFI = Result->begin(); // Get iterator to corresponding fn
58  std::advance(RFI, std::distance(Program->begin(), Module::iterator(PF)));
59
60  Function::iterator RBI = RFI->begin();  // Get iterator to corresponding BB
61  std::advance(RBI, std::distance(PF->begin(), Function::iterator(PBB)));
62
63  BasicBlock::iterator RI = RBI->begin(); // Get iterator to corresponding inst
64  std::advance(RI, std::distance(PBB->begin(), BasicBlock::iterator(I)));
65  I = RI;                                 // Got the corresponding instruction!
66
67  // If this instruction produces a value, replace any users with null values
68  if (I->getType() != Type::VoidTy)
69    I->replaceAllUsesWith(Constant::getNullValue(I->getType()));
70
71  // Remove the instruction from the program.
72  I->getParent()->getInstList().erase(I);
73
74  // Spiff up the output a little bit.
75  PassManager Passes;
76  if (Simplification > 2 && !NoADCE)
77    Passes.add(createAggressiveDCEPass());          // Remove dead code...
78  //Passes.add(createInstructionCombiningPass());
79  if (Simplification > 1 && !NoDCE)
80    Passes.add(createDeadCodeEliminationPass());
81  if (Simplification && !DisableSimplifyCFG)
82    Passes.add(createCFGSimplificationPass());      // Delete dead control flow
83
84  Passes.add(createVerifierPass());
85  Passes.run(*Result);
86  return Result;
87}
88
89/// performFinalCleanups - This method clones the current Program and performs
90/// a series of cleanups intended to get rid of extra cruft on the module
91/// before handing it to the user...
92///
93Module *BugDriver::performFinalCleanups(Module *InM) const {
94  Module *M = InM ? InM : CloneModule(Program);
95
96  // Allow disabling these passes if they crash bugpoint.
97  //
98  // FIXME: This should eventually run these passes in a pass list to prevent
99  // them from being able to crash bugpoint at all!
100  //
101  if (NoFinalCleanup) return M;
102
103  // Make all functions external, so GlobalDCE doesn't delete them...
104  for (Module::iterator I = M->begin(), E = M->end(); I != E; ++I)
105    I->setLinkage(GlobalValue::ExternalLinkage);
106
107  PassManager CleanupPasses;
108  CleanupPasses.add(createFunctionResolvingPass());
109  CleanupPasses.add(createGlobalDCEPass());
110  CleanupPasses.add(createDeadTypeEliminationPass());
111  CleanupPasses.add(createDeadArgEliminationPass(InM == 0));
112  CleanupPasses.add(createVerifierPass());
113  CleanupPasses.run(*M);
114  return M;
115}
116