LLVM  9.0.0svn
Mem2Reg.cpp
Go to the documentation of this file.
1 //===- Mem2Reg.cpp - The -mem2reg pass, a wrapper around the Utils lib ----===//
2 //
3 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
4 // See https://llvm.org/LICENSE.txt for license information.
5 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
6 //
7 //===----------------------------------------------------------------------===//
8 //
9 // This pass is a simple pass wrapper around the PromoteMemToReg function call
10 // exposed by the Utils library.
11 //
12 //===----------------------------------------------------------------------===//
13 
15 #include "llvm/ADT/Statistic.h"
17 #include "llvm/IR/BasicBlock.h"
18 #include "llvm/IR/Dominators.h"
19 #include "llvm/IR/Function.h"
20 #include "llvm/IR/Instructions.h"
21 #include "llvm/IR/PassManager.h"
22 #include "llvm/Pass.h"
23 #include "llvm/Support/Casting.h"
24 #include "llvm/Transforms/Utils.h"
26 #include <vector>
27 
28 using namespace llvm;
29 
30 #define DEBUG_TYPE "mem2reg"
31 
32 STATISTIC(NumPromoted, "Number of alloca's promoted");
33 
35  AssumptionCache &AC) {
36  std::vector<AllocaInst *> Allocas;
37  BasicBlock &BB = F.getEntryBlock(); // Get the entry node for the function
38  bool Changed = false;
39 
40  while (true) {
41  Allocas.clear();
42 
43  // Find allocas that are safe to promote, by looking at all instructions in
44  // the entry node
45  for (BasicBlock::iterator I = BB.begin(), E = --BB.end(); I != E; ++I)
46  if (AllocaInst *AI = dyn_cast<AllocaInst>(I)) // Is it an alloca?
47  if (isAllocaPromotable(AI))
48  Allocas.push_back(AI);
49 
50  if (Allocas.empty())
51  break;
52 
53  PromoteMemToReg(Allocas, DT, &AC);
54  NumPromoted += Allocas.size();
55  Changed = true;
56  }
57  return Changed;
58 }
59 
61  auto &DT = AM.getResult<DominatorTreeAnalysis>(F);
62  auto &AC = AM.getResult<AssumptionAnalysis>(F);
63  if (!promoteMemoryToRegister(F, DT, AC))
64  return PreservedAnalyses::all();
65 
68  return PA;
69 }
70 
71 namespace {
72 
73 struct PromoteLegacyPass : public FunctionPass {
74  // Pass identification, replacement for typeid
75  static char ID;
76 
77  PromoteLegacyPass() : FunctionPass(ID) {
79  }
80 
81  // runOnFunction - To run this pass, first we calculate the alloca
82  // instructions that are safe for promotion, then we promote each one.
83  bool runOnFunction(Function &F) override {
84  if (skipFunction(F))
85  return false;
86 
87  DominatorTree &DT = getAnalysis<DominatorTreeWrapperPass>().getDomTree();
88  AssumptionCache &AC =
89  getAnalysis<AssumptionCacheTracker>().getAssumptionCache(F);
90  return promoteMemoryToRegister(F, DT, AC);
91  }
92 
93  void getAnalysisUsage(AnalysisUsage &AU) const override {
96  AU.setPreservesCFG();
97  }
98 };
99 
100 } // end anonymous namespace
101 
102 char PromoteLegacyPass::ID = 0;
103 
104 INITIALIZE_PASS_BEGIN(PromoteLegacyPass, "mem2reg", "Promote Memory to "
105  "Register",
106  false, false)
109 INITIALIZE_PASS_END(PromoteLegacyPass, "mem2reg", "Promote Memory to Register",
110  false, false)
111 
112 // createPromoteMemoryToRegister - Provide an entry point to create this pass.
114  return new PromoteLegacyPass();
115 }
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:769
This class represents lattice values for constants.
Definition: AllocatorList.h:23
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 @llvm.assume calls within a function.
STATISTIC(NumFunctions, "Total number of functions")
Analysis pass which computes a DominatorTree.
Definition: Dominators.h:230
F(f)
PreservedAnalyses run(Function &F, FunctionAnalysisManager &AM)
Definition: Mem2Reg.cpp:60
bool isAllocaPromotable(const AllocaInst *AI)
Return true if this alloca is legal for promotion.
iterator begin()
Instruction iterator methods.
Definition: BasicBlock.h:268
AnalysisUsage & addRequired()
#define INITIALIZE_PASS_DEPENDENCY(depName)
Definition: PassSupport.h:50
Concrete subclass of DominatorTreeBase that is used to compute a normal dominator tree...
Definition: Dominators.h:144
const BasicBlock & getEntryBlock() const
Definition: Function.h:639
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:57
static GCRegistry::Add< CoreCLRGC > E("coreclr", "CoreCLR-compatible GC")
FunctionPass * createPromoteMemoryToRegisterPass()
Definition: Mem2Reg.cpp:113
Represent the analysis usage information of a pass.
FunctionPass class - This class is used to implement most global optimizations.
Definition: Pass.h:284
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:270
static bool promoteMemoryToRegister(Function &F, DominatorTree &DT, AssumptionCache &AC)
Definition: Mem2Reg.cpp:34
INITIALIZE_PASS_BEGIN(PromoteLegacyPass, "mem2reg", "Promote Memory to " "Register", false, false) INITIALIZE_PASS_END(PromoteLegacyPass
Promote Memory to Register
Definition: Mem2Reg.cpp:109
void setPreservesCFG()
This function should be called by the pass, iff they do not:
Definition: Pass.cpp:301
mem2reg
Definition: Mem2Reg.cpp:109
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:259
This header defines various interfaces for pass management in LLVM.
an instruction to allocate memory on the stack
Definition: Instructions.h:59