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/Analysis/AssumptionCache.h"
18 #include "llvm/IR/Dominators.h"
19 #include "llvm/IR/Function.h"
20 #include "llvm/IR/Instructions.h"
21 #include "llvm/Transforms/Utils/PromoteMemToReg.h"
22 #include "llvm/Transforms/Utils/UnifyFunctionExitNodes.h"
23 using namespace llvm;
24
25 #define DEBUG_TYPE "mem2reg"
26
27 STATISTIC(NumPromoted, "Number of alloca's promoted");
28
29 namespace {
30 struct PromotePass : public FunctionPass {
31 static char ID; // Pass identification, replacement for typeid
PromotePass__anon46344f6b0111::PromotePass32 PromotePass() : FunctionPass(ID) {
33 initializePromotePassPass(*PassRegistry::getPassRegistry());
34 }
35
36 // runOnFunction - To run this pass, first we calculate the alloca
37 // instructions that are safe for promotion, then we promote each one.
38 //
39 bool runOnFunction(Function &F) override;
40
getAnalysisUsage__anon46344f6b0111::PromotePass41 void getAnalysisUsage(AnalysisUsage &AU) const override {
42 AU.addRequired<AssumptionCacheTracker>();
43 AU.addRequired<DominatorTreeWrapperPass>();
44 AU.setPreservesCFG();
45 // This is a cluster of orthogonal Transforms
46 AU.addPreserved<UnifyFunctionExitNodes>();
47 AU.addPreservedID(LowerSwitchID);
48 AU.addPreservedID(LowerInvokePassID);
49 }
50 };
51 } // end of anonymous namespace
52
53 char PromotePass::ID = 0;
54 INITIALIZE_PASS_BEGIN(PromotePass, "mem2reg", "Promote Memory to Register",
55 false, false)
INITIALIZE_PASS_DEPENDENCY(AssumptionCacheTracker)56 INITIALIZE_PASS_DEPENDENCY(AssumptionCacheTracker)
57 INITIALIZE_PASS_DEPENDENCY(DominatorTreeWrapperPass)
58 INITIALIZE_PASS_END(PromotePass, "mem2reg", "Promote Memory to Register",
59 false, false)
60
61 bool PromotePass::runOnFunction(Function &F) {
62 std::vector<AllocaInst*> Allocas;
63
64 BasicBlock &BB = F.getEntryBlock(); // Get the entry node for the function
65
66 if (F.hasFnAttribute(Attribute::OptimizeNone))
67 return false;
68
69 bool Changed = false;
70
71 DominatorTree &DT = getAnalysis<DominatorTreeWrapperPass>().getDomTree();
72 AssumptionCache &AC =
73 getAnalysis<AssumptionCacheTracker>().getAssumptionCache(F);
74
75 while (1) {
76 Allocas.clear();
77
78 // Find allocas that are safe to promote, by looking at all instructions in
79 // the entry node
80 for (BasicBlock::iterator I = BB.begin(), E = --BB.end(); I != E; ++I)
81 if (AllocaInst *AI = dyn_cast<AllocaInst>(I)) // Is it an alloca?
82 if (isAllocaPromotable(AI))
83 Allocas.push_back(AI);
84
85 if (Allocas.empty()) break;
86
87 PromoteMemToReg(Allocas, DT, nullptr, &AC);
88 NumPromoted += Allocas.size();
89 Changed = true;
90 }
91
92 return Changed;
93 }
94
95 // createPromoteMemoryToRegister - Provide an entry point to create this pass.
96 //
createPromoteMemoryToRegisterPass()97 FunctionPass *llvm::createPromoteMemoryToRegisterPass() {
98 return new PromotePass();
99 }
100