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/AliasAnalysis.h"
17 #include "llvm/Analysis/LoopInfo.h"
18 #include "llvm/Analysis/RegionInfo.h"
19 #include "llvm/Analysis/ScalarEvolution.h"
20 #include "llvm/Analysis/ScalarEvolutionExpressions.h"
21 #include "llvm/IR/CFG.h"
22 #include "llvm/Support/Debug.h"
23 #include "llvm/Transforms/Utils/BasicBlockUtils.h"
24 
25 using namespace llvm;
26 
27 #define DEBUG_TYPE "polly-scop-helper"
28 
29 // Helper function for Scop
30 // TODO: Add assertion to not allow parameter to be null
31 //===----------------------------------------------------------------------===//
32 // Temporary Hack for extended region tree.
33 // Cast the region to loop if there is a loop have the same header and exit.
34 Loop *polly::castToLoop(const Region &R, LoopInfo &LI) {
35   BasicBlock *entry = R.getEntry();
36 
37   if (!LI.isLoopHeader(entry))
38     return 0;
39 
40   Loop *L = LI.getLoopFor(entry);
41 
42   BasicBlock *exit = L->getExitBlock();
43 
44   // Is the loop with multiple exits?
45   if (!exit)
46     return 0;
47 
48   if (exit != R.getExit()) {
49     // SubRegion/ParentRegion with the same entry.
50     assert((R.getNode(R.getEntry())->isSubRegion() ||
51             R.getParent()->getEntry() == entry) &&
52            "Expect the loop is the smaller or bigger region");
53     return 0;
54   }
55 
56   return L;
57 }
58 
59 Value *polly::getPointerOperand(Instruction &Inst) {
60   if (LoadInst *load = dyn_cast<LoadInst>(&Inst))
61     return load->getPointerOperand();
62   else if (StoreInst *store = dyn_cast<StoreInst>(&Inst))
63     return store->getPointerOperand();
64   else if (GetElementPtrInst *gep = dyn_cast<GetElementPtrInst>(&Inst))
65     return gep->getPointerOperand();
66 
67   return 0;
68 }
69 
70 Type *polly::getAccessInstType(Instruction *AccInst) {
71   if (StoreInst *Store = dyn_cast<StoreInst>(AccInst))
72     return Store->getValueOperand()->getType();
73   if (BranchInst *Branch = dyn_cast<BranchInst>(AccInst))
74     return Branch->getCondition()->getType();
75   return AccInst->getType();
76 }
77 
78 bool polly::hasInvokeEdge(const PHINode *PN) {
79   for (unsigned i = 0, e = PN->getNumIncomingValues(); i < e; ++i)
80     if (InvokeInst *II = dyn_cast<InvokeInst>(PN->getIncomingValue(i)))
81       if (II->getParent() == PN->getIncomingBlock(i))
82         return true;
83 
84   return false;
85 }
86 
87 BasicBlock *polly::createSingleExitEdge(Region *R, Pass *P) {
88   BasicBlock *BB = R->getExit();
89 
90   SmallVector<BasicBlock *, 4> Preds;
91   for (pred_iterator PI = pred_begin(BB), PE = pred_end(BB); PI != PE; ++PI)
92     if (R->contains(*PI))
93       Preds.push_back(*PI);
94 
95   auto *DTWP = P->getAnalysisIfAvailable<DominatorTreeWrapperPass>();
96   auto *DT = DTWP ? &DTWP->getDomTree() : nullptr;
97   auto *LIWP = P->getAnalysisIfAvailable<LoopInfoWrapperPass>();
98   auto *LI = LIWP ? &LIWP->getLoopInfo() : nullptr;
99 
100   return SplitBlockPredecessors(BB, Preds, ".region", DT, LI);
101 }
102 
103 static void replaceScopAndRegionEntry(polly::Scop *S, BasicBlock *OldEntry,
104                                       BasicBlock *NewEntry) {
105   if (polly::ScopStmt *Stmt = S->getStmtForBasicBlock(OldEntry))
106     Stmt->setBasicBlock(NewEntry);
107 
108   S->getRegion().replaceEntryRecursive(NewEntry);
109 }
110 
111 BasicBlock *polly::simplifyRegion(Scop *S, Pass *P) {
112   Region *R = &S->getRegion();
113 
114   // The entering block for the region.
115   BasicBlock *EnteringBB = R->getEnteringBlock();
116   BasicBlock *OldEntry = R->getEntry();
117   BasicBlock *NewEntry = nullptr;
118 
119   auto *DTWP = P->getAnalysisIfAvailable<DominatorTreeWrapperPass>();
120   auto *DT = DTWP ? &DTWP->getDomTree() : nullptr;
121   auto *LIWP = P->getAnalysisIfAvailable<LoopInfoWrapperPass>();
122   auto *LI = LIWP ? &LIWP->getLoopInfo() : nullptr;
123 
124   // Create single entry edge if the region has multiple entry edges.
125   if (!EnteringBB) {
126     NewEntry = SplitBlock(OldEntry, OldEntry->begin(), DT, LI);
127     EnteringBB = OldEntry;
128   }
129 
130   // Create an unconditional entry edge.
131   if (EnteringBB->getTerminator()->getNumSuccessors() != 1) {
132     BasicBlock *EntryBB = NewEntry ? NewEntry : OldEntry;
133     BasicBlock *SplitEdgeBB = SplitEdge(EnteringBB, EntryBB, DT, LI);
134 
135     // Once the edge between EnteringBB and EntryBB is split, two cases arise.
136     // The first is simple. The new block is inserted between EnteringBB and
137     // EntryBB. In this case no further action is needed. However it might
138     // happen (if the splitted edge is not critical) that the new block is
139     // inserted __after__ EntryBB causing the following situation:
140     //
141     // EnteringBB
142     //    _|_
143     //    | |
144     //    |  \-> some_other_BB_not_in_R
145     //    V
146     // EntryBB
147     //    |
148     //    V
149     // SplitEdgeBB
150     //
151     // In this case we need to swap the role of EntryBB and SplitEdgeBB.
152 
153     // Check which case SplitEdge produced:
154     if (SplitEdgeBB->getTerminator()->getSuccessor(0) == EntryBB) {
155       // First (simple) case.
156       EnteringBB = SplitEdgeBB;
157     } else {
158       // Second (complicated) case.
159       NewEntry = SplitEdgeBB;
160       EnteringBB = EntryBB;
161     }
162 
163     EnteringBB->setName("polly.entering.block");
164   }
165 
166   if (NewEntry)
167     replaceScopAndRegionEntry(S, OldEntry, NewEntry);
168 
169   // Create single exit edge if the region has multiple exit edges.
170   if (!R->getExitingBlock()) {
171     BasicBlock *NewExiting = createSingleExitEdge(R, P);
172     (void)NewExiting;
173     assert(NewExiting == R->getExitingBlock() &&
174            "Did not create a single exiting block");
175   }
176 
177   return EnteringBB;
178 }
179 
180 void polly::splitEntryBlockForAlloca(BasicBlock *EntryBlock, Pass *P) {
181   // Find first non-alloca instruction. Every basic block has a non-alloc
182   // instruction, as every well formed basic block has a terminator.
183   BasicBlock::iterator I = EntryBlock->begin();
184   while (isa<AllocaInst>(I))
185     ++I;
186 
187   auto *DTWP = P->getAnalysisIfAvailable<DominatorTreeWrapperPass>();
188   auto *DT = DTWP ? &DTWP->getDomTree() : nullptr;
189   auto *LIWP = P->getAnalysisIfAvailable<LoopInfoWrapperPass>();
190   auto *LI = LIWP ? &LIWP->getLoopInfo() : nullptr;
191 
192   // SplitBlock updates DT, DF and LI.
193   BasicBlock *NewEntry = SplitBlock(EntryBlock, I, DT, LI);
194   if (RegionInfoPass *RIP = P->getAnalysisIfAvailable<RegionInfoPass>())
195     RIP->getRegionInfo().splitBlock(NewEntry, EntryBlock);
196 }
197