LLVM  6.0.0svn
Mem2Reg.cpp
Go to the documentation of this file.
1 //===- Mem2Reg.cpp - The -mem2reg pass, a wrapper around the Utils lib ----===//
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 is a simple pass wrapper around the PromoteMemToReg function call
11 // exposed by the Utils library.
12 //
13 //===----------------------------------------------------------------------===//
14 
16 #include "llvm/ADT/Statistic.h"
18 #include "llvm/IR/BasicBlock.h"
19 #include "llvm/IR/Dominators.h"
20 #include "llvm/IR/Function.h"
21 #include "llvm/IR/Instructions.h"
22 #include "llvm/IR/PassManager.h"
23 #include "llvm/Pass.h"
24 #include "llvm/Support/Casting.h"
25 #include "llvm/Transforms/Scalar.h"
27 #include <vector>
28 
29 using namespace llvm;
30 
31 #define DEBUG_TYPE "mem2reg"
32 
33 STATISTIC(NumPromoted, "Number of alloca's promoted");
34 
36  AssumptionCache &AC) {
37  std::vector<AllocaInst *> Allocas;
38  BasicBlock &BB = F.getEntryBlock(); // Get the entry node for the function
39  bool Changed = false;
40 
41  while (true) {
42  Allocas.clear();
43 
44  // Find allocas that are safe to promote, by looking at all instructions in
45  // the entry node
46  for (BasicBlock::iterator I = BB.begin(), E = --BB.end(); I != E; ++I)
47  if (AllocaInst *AI = dyn_cast<AllocaInst>(I)) // Is it an alloca?
48  if (isAllocaPromotable(AI))
49  Allocas.push_back(AI);
50 
51  if (Allocas.empty())
52  break;
53 
54  PromoteMemToReg(Allocas, DT, &AC);
55  NumPromoted += Allocas.size();
56  Changed = true;
57  }
58  return Changed;
59 }
60 
62  auto &DT = AM.getResult<DominatorTreeAnalysis>(F);
63  auto &AC = AM.getResult<AssumptionAnalysis>(F);
64  if (!promoteMemoryToRegister(F, DT, AC))
65  return PreservedAnalyses::all();
66 
69  return PA;
70 }
71 
72 namespace {
73 
74 struct PromoteLegacyPass : public FunctionPass {
75  // Pass identification, replacement for typeid
76  static char ID;
77 
78  PromoteLegacyPass() : FunctionPass(ID) {
80  }
81 
82  // runOnFunction - To run this pass, first we calculate the alloca
83  // instructions that are safe for promotion, then we promote each one.
84  bool runOnFunction(Function &F) override {
85  if (skipFunction(F))
86  return false;
87 
88  DominatorTree &DT = getAnalysis<DominatorTreeWrapperPass>().getDomTree();
89  AssumptionCache &AC =
90  getAnalysis<AssumptionCacheTracker>().getAssumptionCache(F);
91  return promoteMemoryToRegister(F, DT, AC);
92  }
93 
94  void getAnalysisUsage(AnalysisUsage &AU) const override {
97  AU.setPreservesCFG();
98  }
99 };
100 
101 } // end anonymous namespace
102 
103 char PromoteLegacyPass::ID = 0;
104 
105 INITIALIZE_PASS_BEGIN(PromoteLegacyPass, "mem2reg", "Promote Memory to "
106  "Register",
107  false, false)
110 INITIALIZE_PASS_END(PromoteLegacyPass, "mem2reg", "Promote Memory to Register",
111  false, false)
112 
113 // createPromoteMemoryToRegister - Provide an entry point to create this pass.
115  return new PromoteLegacyPass();
116 }
static PassRegistry * getPassRegistry()
getPassRegistry - Access the global registry object, which is automatically initialized at applicatio...
PassT::Result & getResult(IRUnitT &IR, ExtraArgTs... ExtraArgs)
Get the result of an analysis pass for a given IR unit.
Definition: PassManager.h:687
Compute iterated dominance frontiers using a linear time algorithm.
Definition: AllocatorList.h:24
This class provides various memory handling functions that manipulate MemoryBlock instances...
Definition: Memory.h:46
An immutable pass that tracks lazily created AssumptionCache objects.
A cache of .assume calls within a function.
STATISTIC(NumFunctions, "Total number of functions")
Analysis pass which computes a DominatorTree.
Definition: Dominators.h:238
F(f)
PreservedAnalyses run(Function &F, FunctionAnalysisManager &AM)
Definition: Mem2Reg.cpp:61
bool isAllocaPromotable(const AllocaInst *AI)
Return true if this alloca is legal for promotion.
iterator begin()
Instruction iterator methods.
Definition: BasicBlock.h:252
AnalysisUsage & addRequired()
#define INITIALIZE_PASS_DEPENDENCY(depName)
Definition: PassSupport.h:51
Concrete subclass of DominatorTreeBase that is used to compute a normal dominator tree...
Definition: Dominators.h:140
const BasicBlock & getEntryBlock() const
Definition: Function.h:572
static bool runOnFunction(Function &F, bool PostInlining)
A set of analyses that are preserved following a run of a transformation pass.
Definition: PassManager.h:153
LLVM Basic Block Representation.
Definition: BasicBlock.h:59
static GCRegistry::Add< CoreCLRGC > E("coreclr", "CoreCLR-compatible GC")
FunctionPass * createPromoteMemoryToRegisterPass()
Definition: Mem2Reg.cpp:114
Represent the analysis usage information of a pass.
FunctionPass class - This class is used to implement most global optimizations.
Definition: Pass.h:285
static PreservedAnalyses all()
Construct a special preserved set that preserves all passes.
Definition: PassManager.h:159
INITIALIZE_PASS_END(RegBankSelect, DEBUG_TYPE, "Assign register bank of generic virtual registers", false, false) RegBankSelect
A function analysis which provides an AssumptionCache.
Iterator for intrusive lists based on ilist_node.
iterator end()
Definition: BasicBlock.h:254
static bool promoteMemoryToRegister(Function &F, DominatorTree &DT, AssumptionCache &AC)
Definition: Mem2Reg.cpp:35
INITIALIZE_PASS_BEGIN(PromoteLegacyPass, "mem2reg", "Promote Memory to " "Register", false, false) INITIALIZE_PASS_END(PromoteLegacyPass
Promote Memory to Register
Definition: Mem2Reg.cpp:110
void setPreservesCFG()
This function should be called by the pass, iff they do not:
Definition: Pass.cpp:285
mem2reg
Definition: Mem2Reg.cpp:110
void initializePromoteLegacyPassPass(PassRegistry &)
Represents analyses that only rely on functions&#39; control flow.
Definition: PassManager.h:114
void preserveSet()
Mark an analysis set as preserved.
Definition: PassManager.h:189
#define I(x, y, z)
Definition: MD5.cpp:58
void PromoteMemToReg(ArrayRef< AllocaInst *> Allocas, DominatorTree &DT, AssumptionCache *AC=nullptr)
Promote the specified list of alloca instructions into scalar registers, inserting PHI nodes as appro...
A container for analyses that lazily runs them and caches their results.
Legacy analysis pass which computes a DominatorTree.
Definition: Dominators.h:267
This header defines various interfaces for pass management in LLVM.
an instruction to allocate memory on the stack
Definition: Instructions.h:60