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
15 #include "llvm/Transforms/Scalar.h"
16 #include "llvm/ADT/Statistic.h"
17 #include "llvm/IR/Dominators.h"
18 #include "llvm/IR/Function.h"
19 #include "llvm/IR/Instructions.h"
20 #include "llvm/Transforms/Utils/PromoteMemToReg.h"
21 #include "llvm/Transforms/Utils/UnifyFunctionExitNodes.h"
22 using namespace llvm;
23
24 #define DEBUG_TYPE "mem2reg"
25
26 STATISTIC(NumPromoted, "Number of alloca's promoted");
27
28 namespace {
29 struct PromotePass : public FunctionPass {
30 static char ID; // Pass identification, replacement for typeid
PromotePass__anon65057a630111::PromotePass31 PromotePass() : FunctionPass(ID) {
32 initializePromotePassPass(*PassRegistry::getPassRegistry());
33 }
34
35 // runOnFunction - To run this pass, first we calculate the alloca
36 // instructions that are safe for promotion, then we promote each one.
37 //
38 bool runOnFunction(Function &F) override;
39
getAnalysisUsage__anon65057a630111::PromotePass40 void getAnalysisUsage(AnalysisUsage &AU) const override {
41 AU.addRequired<DominatorTreeWrapperPass>();
42 AU.setPreservesCFG();
43 // This is a cluster of orthogonal Transforms
44 AU.addPreserved<UnifyFunctionExitNodes>();
45 AU.addPreservedID(LowerSwitchID);
46 AU.addPreservedID(LowerInvokePassID);
47 }
48 };
49 } // end of anonymous namespace
50
51 char PromotePass::ID = 0;
52 INITIALIZE_PASS_BEGIN(PromotePass, "mem2reg", "Promote Memory to Register",
53 false, false)
INITIALIZE_PASS_DEPENDENCY(DominatorTreeWrapperPass)54 INITIALIZE_PASS_DEPENDENCY(DominatorTreeWrapperPass)
55 INITIALIZE_PASS_END(PromotePass, "mem2reg", "Promote Memory to Register",
56 false, false)
57
58 bool PromotePass::runOnFunction(Function &F) {
59 std::vector<AllocaInst*> Allocas;
60
61 BasicBlock &BB = F.getEntryBlock(); // Get the entry node for the function
62
63 bool Changed = false;
64
65 DominatorTree &DT = getAnalysis<DominatorTreeWrapperPass>().getDomTree();
66
67 while (1) {
68 Allocas.clear();
69
70 // Find allocas that are safe to promote, by looking at all instructions in
71 // the entry node
72 for (BasicBlock::iterator I = BB.begin(), E = --BB.end(); I != E; ++I)
73 if (AllocaInst *AI = dyn_cast<AllocaInst>(I)) // Is it an alloca?
74 if (isAllocaPromotable(AI))
75 Allocas.push_back(AI);
76
77 if (Allocas.empty()) break;
78
79 PromoteMemToReg(Allocas, DT);
80 NumPromoted += Allocas.size();
81 Changed = true;
82 }
83
84 return Changed;
85 }
86
87 // createPromoteMemoryToRegister - Provide an entry point to create this pass.
88 //
createPromoteMemoryToRegisterPass()89 FunctionPass *llvm::createPromoteMemoryToRegisterPass() {
90 return new PromotePass();
91 }
92