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 #include "polly/Support/PollyDebug.h"
25 #define DEBUG_TYPE "polly-scop-inliner"
26
27 using namespace llvm;
28 using namespace polly;
29
30 namespace {
31 class ScopInliner final : public CallGraphSCCPass {
32 using llvm::Pass::doInitialization;
33
34 public:
35 static char ID;
36
ScopInliner()37 ScopInliner() : CallGraphSCCPass(ID) {}
38
doInitialization(CallGraph & CG)39 bool doInitialization(CallGraph &CG) override {
40 if (!polly::PollyAllowFullFunction) {
41 report_fatal_error(
42 "Aborting from ScopInliner because it only makes sense to run with "
43 "-polly-allow-full-function. "
44 "The heurtistic for ScopInliner checks that the full function is a "
45 "Scop, which happens if and only if polly-allow-full-function is "
46 " enabled. "
47 " If not, the entry block is not included in the Scop");
48 }
49 return true;
50 }
51
runOnSCC(CallGraphSCC & SCC)52 bool runOnSCC(CallGraphSCC &SCC) override {
53 // We do not try to inline non-trivial SCCs because this would lead to
54 // "infinite" inlining if we are not careful.
55 if (SCC.size() > 1)
56 return false;
57 assert(SCC.size() == 1 && "found empty SCC");
58 Function *F = (*SCC.begin())->getFunction();
59
60 // If the function is a nullptr, or the function is a declaration.
61 if (!F)
62 return false;
63 if (F->isDeclaration()) {
64 POLLY_DEBUG(dbgs() << "Skipping " << F->getName()
65 << "because it is a declaration.\n");
66 return false;
67 }
68
69 PassBuilder PB;
70 // Populate analysis managers and register Polly-specific analyses.
71 LoopAnalysisManager LAM;
72 FunctionAnalysisManager FAM;
73 CGSCCAnalysisManager CGAM;
74 ModuleAnalysisManager MAM;
75 FAM.registerPass([] { return ScopAnalysis(); });
76 PB.registerModuleAnalyses(MAM);
77 PB.registerCGSCCAnalyses(CGAM);
78 PB.registerFunctionAnalyses(FAM);
79 PB.registerLoopAnalyses(LAM);
80 PB.crossRegisterProxies(LAM, FAM, CGAM, MAM);
81
82 RegionInfo &RI = FAM.getResult<RegionInfoAnalysis>(*F);
83 ScopDetection &SD = FAM.getResult<ScopAnalysis>(*F);
84
85 const bool HasScopAsTopLevelRegion =
86 SD.ValidRegions.contains(RI.getTopLevelRegion());
87
88 bool Changed = false;
89 if (HasScopAsTopLevelRegion) {
90 POLLY_DEBUG(dbgs() << "Skipping " << F->getName()
91 << " has scop as top level region");
92 F->addFnAttr(llvm::Attribute::AlwaysInline);
93
94 ModulePassManager MPM;
95 MPM.addPass(AlwaysInlinerPass());
96 Module *M = F->getParent();
97 assert(M && "Function has illegal module");
98 PreservedAnalyses PA = MPM.run(*M, MAM);
99 if (!PA.areAllPreserved())
100 Changed = true;
101 } else {
102 POLLY_DEBUG(dbgs() << F->getName()
103 << " does NOT have scop as top level region\n");
104 }
105
106 return Changed;
107 };
108
getAnalysisUsage(AnalysisUsage & AU) const109 void getAnalysisUsage(AnalysisUsage &AU) const override {
110 CallGraphSCCPass::getAnalysisUsage(AU);
111 }
112 };
113 } // namespace
114 char ScopInliner::ID;
115
createScopInlinerPass()116 Pass *polly::createScopInlinerPass() {
117 ScopInliner *pass = new ScopInliner();
118 return pass;
119 }
120
121 INITIALIZE_PASS_BEGIN(
122 ScopInliner, "polly-scop-inliner",
123 "inline functions based on how much of the function is a scop.", false,
124 false)
125 INITIALIZE_PASS_END(
126 ScopInliner, "polly-scop-inliner",
127 "inline functions based on how much of the function is a scop.", false,
128 false)
129