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 
16 #include "polly/ScopInfo.h"
17 
18 #include "llvm/IRBuilder.h"
19 #include "llvm/Support/Debug.h"
20 #include "llvm/Transforms/Utils/BasicBlockUtils.h"
21 
22 using namespace llvm;
23 
24 BasicBlock *polly::executeScopConditionally(Scop &S, Pass *PassInfo) {
25   BasicBlock *StartBlock, *SplitBlock, *NewBlock;
26   Region &R = S.getRegion();
27   IRBuilder<> Builder(R.getEntry());
28   DominatorTree &DT = PassInfo->getAnalysis<DominatorTree>();
29   RegionInfo &RI = PassInfo->getAnalysis<RegionInfo>();
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(), PassInfo);
34   if (DT.dominates(R.getEntry(), NewBlock)) {
35     BasicBlock *OldBlock = R.getEntry();
36     std::string OldName = OldBlock->getName();
37 
38     // Update ScopInfo.
39     for (Scop::iterator SI = S.begin(), SE = S.end(); SI != SE; ++SI)
40       if ((*SI)->getBasicBlock() == OldBlock) {
41         (*SI)->setBasicBlock(NewBlock);
42         break;
43       }
44 
45     // Update RegionInfo.
46     SplitBlock = OldBlock;
47     OldBlock->setName("polly.split");
48     NewBlock->setName(OldName);
49     R.replaceEntry(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(Builder.getTrue(), StartBlock, R.getEntry());
62   DT.addNewBlock(StartBlock, SplitBlock);
63   Builder.SetInsertPoint(StartBlock);
64 
65   BasicBlock *MergeBlock;
66 
67   if (R.getExit()->getSinglePredecessor())
68     // No splitEdge required.  A block with a single predecessor cannot have
69     // PHI nodes that would complicate life.
70     MergeBlock = R.getExit();
71   else {
72     MergeBlock = SplitEdge(R.getExitingBlock(), R.getExit(), PassInfo);
73     // SplitEdge will never split R.getExit(), as R.getExit() has more than
74     // one predecessor. Hence, mergeBlock is always a newly generated block.
75     R.replaceExit(MergeBlock);
76   }
77 
78   Builder.CreateBr(MergeBlock);
79   MergeBlock->setName("polly.merge_new_and_old");
80 
81   if (DT.dominates(SplitBlock, MergeBlock))
82     DT.changeImmediateDominator(MergeBlock, SplitBlock);
83   return StartBlock;
84 }
85