1 //===--- Utils.cpp - Utility functions for the code generation --*- C++ -*-===//
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 file contains utility functions for the code generation.
11 //
12 //===----------------------------------------------------------------------===//
13 
14 #include "polly/CodeGen/Utils.h"
15 #include "polly/CodeGen/IRBuilder.h"
16 #include "polly/ScopInfo.h"
17 #include "llvm/Analysis/LoopInfo.h"
18 #include "llvm/Support/Debug.h"
19 #include "llvm/Transforms/Utils/BasicBlockUtils.h"
20 
21 using namespace llvm;
22 
23 BasicBlock *polly::executeScopConditionally(Scop &S, Pass *P, Value *RTC) {
24   BasicBlock *StartBlock, *SplitBlock, *NewBlock;
25   Region &R = S.getRegion();
26   PollyIRBuilder Builder(R.getEntry());
27   DominatorTree &DT = P->getAnalysis<DominatorTreeWrapperPass>().getDomTree();
28   RegionInfo &RI = P->getAnalysis<RegionInfoPass>().getRegionInfo();
29   LoopInfo &LI = P->getAnalysis<LoopInfo>();
30 
31   // Split the entry edge of the region and generate a new basic block on this
32   // edge. This function also updates ScopInfo and RegionInfo.
33   NewBlock = SplitEdge(R.getEnteringBlock(), R.getEntry(), P);
34   if (DT.dominates(R.getEntry(), NewBlock)) {
35     BasicBlock *OldBlock = R.getEntry();
36     std::string OldName = OldBlock->getName();
37 
38     // Update ScopInfo.
39     for (ScopStmt *Stmt : S)
40       if (Stmt->getBasicBlock() == OldBlock) {
41         Stmt->setBasicBlock(NewBlock);
42         break;
43       }
44 
45     // Update RegionInfo.
46     SplitBlock = OldBlock;
47     OldBlock->setName("polly.split");
48     NewBlock->setName(OldName);
49     R.replaceEntryRecursive(NewBlock);
50     RI.setRegionFor(NewBlock, &R);
51   } else {
52     RI.setRegionFor(NewBlock, R.getParent());
53     SplitBlock = NewBlock;
54   }
55 
56   SplitBlock->setName("polly.split_new_and_old");
57   Function *F = SplitBlock->getParent();
58   StartBlock = BasicBlock::Create(F->getContext(), "polly.start", F);
59   SplitBlock->getTerminator()->eraseFromParent();
60   Builder.SetInsertPoint(SplitBlock);
61   Builder.CreateCondBr(RTC, StartBlock, R.getEntry());
62   if (Loop *L = LI.getLoopFor(SplitBlock))
63     L->addBasicBlockToLoop(StartBlock, LI.getBase());
64   DT.addNewBlock(StartBlock, SplitBlock);
65   Builder.SetInsertPoint(StartBlock);
66 
67   BasicBlock *MergeBlock;
68 
69   if (R.getExit()->getSinglePredecessor())
70     // No splitEdge required.  A block with a single predecessor cannot have
71     // PHI nodes that would complicate life.
72     MergeBlock = R.getExit();
73   else {
74     MergeBlock = SplitEdge(R.getExitingBlock(), R.getExit(), P);
75     // SplitEdge will never split R.getExit(), as R.getExit() has more than
76     // one predecessor. Hence, mergeBlock is always a newly generated block.
77     R.replaceExitRecursive(MergeBlock);
78     RI.setRegionFor(MergeBlock, &R);
79   }
80 
81   Builder.CreateBr(MergeBlock);
82   MergeBlock->setName("polly.merge_new_and_old");
83 
84   if (DT.dominates(SplitBlock, MergeBlock))
85     DT.changeImmediateDominator(MergeBlock, SplitBlock);
86   return StartBlock;
87 }
88