1 //===- ScopHelper.cpp - Some Helper Functions for Scop.  ------------------===//
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 // Small functions that help with Scop and LLVM-IR.
11 //
12 //===----------------------------------------------------------------------===//
13 
14 #include "polly/Support/ScopHelper.h"
15 #include "polly/ScopInfo.h"
16 #include "llvm/Analysis/LoopInfo.h"
17 #include "llvm/Analysis/RegionInfo.h"
18 #include "llvm/Analysis/ScalarEvolution.h"
19 #include "llvm/Analysis/ScalarEvolutionExpressions.h"
20 #include "llvm/IR/CFG.h"
21 #include "llvm/Support/Debug.h"
22 #include "llvm/Transforms/Utils/BasicBlockUtils.h"
23 
24 using namespace llvm;
25 
26 #define DEBUG_TYPE "polly-scop-helper"
27 
28 // Helper function for Scop
29 // TODO: Add assertion to not allow parameter to be null
30 //===----------------------------------------------------------------------===//
31 // Temporary Hack for extended region tree.
32 // Cast the region to loop if there is a loop have the same header and exit.
33 Loop *polly::castToLoop(const Region &R, LoopInfo &LI) {
34   BasicBlock *entry = R.getEntry();
35 
36   if (!LI.isLoopHeader(entry))
37     return 0;
38 
39   Loop *L = LI.getLoopFor(entry);
40 
41   BasicBlock *exit = L->getExitBlock();
42 
43   // Is the loop with multiple exits?
44   if (!exit)
45     return 0;
46 
47   if (exit != R.getExit()) {
48     // SubRegion/ParentRegion with the same entry.
49     assert((R.getNode(R.getEntry())->isSubRegion() ||
50             R.getParent()->getEntry() == entry) &&
51            "Expect the loop is the smaller or bigger region");
52     return 0;
53   }
54 
55   return L;
56 }
57 
58 Value *polly::getPointerOperand(Instruction &Inst) {
59   if (LoadInst *load = dyn_cast<LoadInst>(&Inst))
60     return load->getPointerOperand();
61   else if (StoreInst *store = dyn_cast<StoreInst>(&Inst))
62     return store->getPointerOperand();
63   else if (GetElementPtrInst *gep = dyn_cast<GetElementPtrInst>(&Inst))
64     return gep->getPointerOperand();
65 
66   return 0;
67 }
68 
69 bool polly::hasInvokeEdge(const PHINode *PN) {
70   for (unsigned i = 0, e = PN->getNumIncomingValues(); i < e; ++i)
71     if (InvokeInst *II = dyn_cast<InvokeInst>(PN->getIncomingValue(i)))
72       if (II->getParent() == PN->getIncomingBlock(i))
73         return true;
74 
75   return false;
76 }
77 
78 BasicBlock *polly::createSingleExitEdge(Region *R, Pass *P) {
79   BasicBlock *BB = R->getExit();
80 
81   SmallVector<BasicBlock *, 4> Preds;
82   for (pred_iterator PI = pred_begin(BB), PE = pred_end(BB); PI != PE; ++PI)
83     if (R->contains(*PI))
84       Preds.push_back(*PI);
85 
86   return SplitBlockPredecessors(BB, Preds, ".region", P);
87 }
88 
89 void polly::simplifyRegion(Scop *S, Pass *P) {
90   Region *R = &S->getRegion();
91 
92   // Create single entry edge if the region has multiple entry edges.
93   if (!R->getEnteringBlock()) {
94     BasicBlock *OldEntry = R->getEntry();
95     BasicBlock *NewEntry = SplitBlock(OldEntry, OldEntry->begin(), P);
96 
97     for (ScopStmt *Stmt : *S)
98       if (Stmt->getBasicBlock() == OldEntry) {
99         Stmt->setBasicBlock(NewEntry);
100         break;
101       }
102 
103     R->replaceEntryRecursive(NewEntry);
104   }
105 
106   // Create single exit edge if the region has multiple exit edges.
107   if (!R->getExitingBlock()) {
108     BasicBlock *NewExit = createSingleExitEdge(R, P);
109 
110     for (auto &&SubRegion : *R)
111       SubRegion->replaceExitRecursive(NewExit);
112   }
113 }
114 
115 void polly::splitEntryBlockForAlloca(BasicBlock *EntryBlock, Pass *P) {
116   // Find first non-alloca instruction. Every basic block has a non-alloc
117   // instruction, as every well formed basic block has a terminator.
118   BasicBlock::iterator I = EntryBlock->begin();
119   while (isa<AllocaInst>(I))
120     ++I;
121 
122   // SplitBlock updates DT, DF and LI.
123   BasicBlock *NewEntry = SplitBlock(EntryBlock, I, P);
124   if (RegionInfoPass *RIP = P->getAnalysisIfAvailable<RegionInfoPass>())
125     RIP->getRegionInfo().splitBlock(NewEntry, EntryBlock);
126 }
127