1 //===---- CodePreparation.cpp - Code preparation for Scop Detection -------===//
2 //
3 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
4 // See https://llvm.org/LICENSE.txt for license information.
5 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
6 //
7 //===----------------------------------------------------------------------===//
8 //
9 // The Polly code preparation pass is executed before SCoP detection. Its
10 // currently only splits the entry block of the SCoP to make room for alloc
11 // instructions as they are generated during code generation.
12 //
13 // XXX: In the future, we should remove the need for this pass entirely and
14 // instead add this spitting to the code generation pass.
15 //
16 //===----------------------------------------------------------------------===//
17
18 #include "polly/CodePreparation.h"
19 #include "polly/LinkAllPasses.h"
20 #include "polly/Support/ScopHelper.h"
21 #include "llvm/Analysis/DominanceFrontier.h"
22 #include "llvm/Analysis/LoopInfo.h"
23 #include "llvm/Analysis/RegionInfo.h"
24 #include "llvm/Analysis/ScalarEvolution.h"
25 #include "llvm/InitializePasses.h"
26
27 using namespace llvm;
28 using namespace polly;
29
30 namespace {
31
32 /// Prepare the IR for the scop detection.
33 ///
34 class CodePreparation : public FunctionPass {
35 CodePreparation(const CodePreparation &) = delete;
36 const CodePreparation &operator=(const CodePreparation &) = delete;
37
38 LoopInfo *LI;
39 ScalarEvolution *SE;
40
41 void clear();
42
43 public:
44 static char ID;
45
CodePreparation()46 explicit CodePreparation() : FunctionPass(ID) {}
47 ~CodePreparation();
48
49 /// @name FunctionPass interface.
50 //@{
51 void getAnalysisUsage(AnalysisUsage &AU) const override;
52 void releaseMemory() override;
53 bool runOnFunction(Function &F) override;
54 void print(raw_ostream &OS, const Module *) const override;
55 //@}
56 };
57 } // namespace
58
run(Function & F,FunctionAnalysisManager & FAM)59 PreservedAnalyses CodePreparationPass::run(Function &F,
60 FunctionAnalysisManager &FAM) {
61
62 // Find first non-alloca instruction. Every basic block has a non-alloca
63 // instruction, as every well formed basic block has a terminator.
64 auto &EntryBlock = F.getEntryBlock();
65 BasicBlock::iterator I = EntryBlock.begin();
66 while (isa<AllocaInst>(I))
67 ++I;
68
69 auto &DT = FAM.getResult<DominatorTreeAnalysis>(F);
70 auto &LI = FAM.getResult<LoopAnalysis>(F);
71
72 // splitBlock updates DT, LI and RI.
73 splitEntryBlockForAlloca(&EntryBlock, &DT, &LI, nullptr);
74
75 PreservedAnalyses PA;
76 PA.preserve<DominatorTreeAnalysis>();
77 PA.preserve<LoopAnalysis>();
78 return PA;
79 }
80
clear()81 void CodePreparation::clear() {}
82
~CodePreparation()83 CodePreparation::~CodePreparation() { clear(); }
84
getAnalysisUsage(AnalysisUsage & AU) const85 void CodePreparation::getAnalysisUsage(AnalysisUsage &AU) const {
86 AU.addRequired<LoopInfoWrapperPass>();
87 AU.addRequired<ScalarEvolutionWrapperPass>();
88
89 AU.addPreserved<LoopInfoWrapperPass>();
90 AU.addPreserved<RegionInfoPass>();
91 AU.addPreserved<DominatorTreeWrapperPass>();
92 AU.addPreserved<DominanceFrontierWrapperPass>();
93 }
94
runOnFunction(Function & F)95 bool CodePreparation::runOnFunction(Function &F) {
96 if (skipFunction(F))
97 return false;
98
99 LI = &getAnalysis<LoopInfoWrapperPass>().getLoopInfo();
100 SE = &getAnalysis<ScalarEvolutionWrapperPass>().getSE();
101
102 splitEntryBlockForAlloca(&F.getEntryBlock(), this);
103
104 return true;
105 }
106
releaseMemory()107 void CodePreparation::releaseMemory() { clear(); }
108
print(raw_ostream & OS,const Module *) const109 void CodePreparation::print(raw_ostream &OS, const Module *) const {}
110
111 char CodePreparation::ID = 0;
112 char &polly::CodePreparationID = CodePreparation::ID;
113
createCodePreparationPass()114 Pass *polly::createCodePreparationPass() { return new CodePreparation(); }
115
116 INITIALIZE_PASS_BEGIN(CodePreparation, "polly-prepare",
117 "Polly - Prepare code for polly", false, false)
118 INITIALIZE_PASS_DEPENDENCY(LoopInfoWrapperPass)
119 INITIALIZE_PASS_END(CodePreparation, "polly-prepare",
120 "Polly - Prepare code for polly", false, false)
121