1 //===---- ScopInliner.cpp - Polyhedral based inliner ----------------------===//
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 // Take a SCC and:
10 // 1. If it has more than one component, bail out (contains cycles)
11 // 2. If it has just one component, and if the function is entirely a scop,
12 // inline it.
13 //
14 //===----------------------------------------------------------------------===//
15
16 #include "polly/LinkAllPasses.h"
17 #include "polly/ScopDetection.h"
18 #include "llvm/Analysis/CallGraph.h"
19 #include "llvm/Analysis/CallGraphSCCPass.h"
20 #include "llvm/IR/PassManager.h"
21 #include "llvm/Passes/PassBuilder.h"
22 #include "llvm/Transforms/IPO/AlwaysInliner.h"
23
24 #define DEBUG_TYPE "polly-scop-inliner"
25
26 using namespace llvm;
27 using namespace polly;
28
29 namespace {
30 class ScopInliner final : public CallGraphSCCPass {
31 using llvm::Pass::doInitialization;
32
33 public:
34 static char ID;
35
ScopInliner()36 ScopInliner() : CallGraphSCCPass(ID) {}
37
doInitialization(CallGraph & CG)38 bool doInitialization(CallGraph &CG) override {
39 if (!polly::PollyAllowFullFunction) {
40 report_fatal_error(
41 "Aborting from ScopInliner because it only makes sense to run with "
42 "-polly-allow-full-function. "
43 "The heurtistic for ScopInliner checks that the full function is a "
44 "Scop, which happens if and only if polly-allow-full-function is "
45 " enabled. "
46 " If not, the entry block is not included in the Scop");
47 }
48 return true;
49 }
50
runOnSCC(CallGraphSCC & SCC)51 bool runOnSCC(CallGraphSCC &SCC) override {
52 // We do not try to inline non-trivial SCCs because this would lead to
53 // "infinite" inlining if we are not careful.
54 if (SCC.size() > 1)
55 return false;
56 assert(SCC.size() == 1 && "found empty SCC");
57 Function *F = (*SCC.begin())->getFunction();
58
59 // If the function is a nullptr, or the function is a declaration.
60 if (!F)
61 return false;
62 if (F->isDeclaration()) {
63 LLVM_DEBUG(dbgs() << "Skipping " << F->getName()
64 << "because it is a declaration.\n");
65 return false;
66 }
67
68 PassBuilder PB;
69 // Populate analysis managers and register Polly-specific analyses.
70 LoopAnalysisManager LAM;
71 FunctionAnalysisManager FAM;
72 CGSCCAnalysisManager CGAM;
73 ModuleAnalysisManager MAM;
74 FAM.registerPass([] { return ScopAnalysis(); });
75 PB.registerModuleAnalyses(MAM);
76 PB.registerCGSCCAnalyses(CGAM);
77 PB.registerFunctionAnalyses(FAM);
78 PB.registerLoopAnalyses(LAM);
79 PB.crossRegisterProxies(LAM, FAM, CGAM, MAM);
80
81 RegionInfo &RI = FAM.getResult<RegionInfoAnalysis>(*F);
82 ScopDetection &SD = FAM.getResult<ScopAnalysis>(*F);
83
84 const bool HasScopAsTopLevelRegion =
85 SD.ValidRegions.contains(RI.getTopLevelRegion());
86
87 bool Changed = false;
88 if (HasScopAsTopLevelRegion) {
89 LLVM_DEBUG(dbgs() << "Skipping " << F->getName()
90 << " has scop as top level region");
91 F->addFnAttr(llvm::Attribute::AlwaysInline);
92
93 ModulePassManager MPM;
94 MPM.addPass(AlwaysInlinerPass());
95 Module *M = F->getParent();
96 assert(M && "Function has illegal module");
97 PreservedAnalyses PA = MPM.run(*M, MAM);
98 if (!PA.areAllPreserved())
99 Changed = true;
100 } else {
101 LLVM_DEBUG(dbgs() << F->getName()
102 << " does NOT have scop as top level region\n");
103 }
104
105 return Changed;
106 };
107
getAnalysisUsage(AnalysisUsage & AU) const108 void getAnalysisUsage(AnalysisUsage &AU) const override {
109 CallGraphSCCPass::getAnalysisUsage(AU);
110 }
111 };
112 } // namespace
113 char ScopInliner::ID;
114
createScopInlinerPass()115 Pass *polly::createScopInlinerPass() {
116 ScopInliner *pass = new ScopInliner();
117 return pass;
118 }
119
120 INITIALIZE_PASS_BEGIN(
121 ScopInliner, "polly-scop-inliner",
122 "inline functions based on how much of the function is a scop.", false,
123 false)
124 INITIALIZE_PASS_END(
125 ScopInliner, "polly-scop-inliner",
126 "inline functions based on how much of the function is a scop.", false,
127 false)
128