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