1 //===- Inliner.cpp - Code common to all inliners --------------------------===//
3 // The LLVM Compiler Infrastructure
5 // This file was developed by the LLVM research group and is distributed under
6 // the University of Illinois Open Source License. See LICENSE.TXT for details.
8 //===----------------------------------------------------------------------===//
10 // This file implements the mechanics required to implement inlining without
11 // missing any calls and updating the call graph. The decisions of which calls
12 // are profitable to inline are implemented elsewhere.
14 //===----------------------------------------------------------------------===//
16 #define DEBUG_TYPE "inline"
18 #include "llvm/Module.h"
19 #include "llvm/Instructions.h"
20 #include "llvm/Analysis/CallGraph.h"
21 #include "llvm/Support/CallSite.h"
22 #include "llvm/Target/TargetData.h"
23 #include "llvm/Transforms/Utils/Cloning.h"
24 #include "llvm/Support/CommandLine.h"
25 #include "llvm/Support/Debug.h"
26 #include "llvm/ADT/Statistic.h"
30 STATISTIC(NumInlined, "Number of functions inlined");
31 STATISTIC(NumDeleted, "Number of functions deleted because all callers found");
34 cl::opt<unsigned> // FIXME: 200 is VERY conservative
35 InlineLimit("inline-threshold", cl::Hidden, cl::init(200),
36 cl::desc("Control the amount of inlining to perform (default = 200)"));
39 Inliner::Inliner() : InlineThreshold(InlineLimit) {}
41 /// getAnalysisUsage - For this class, we declare that we require and preserve
42 /// the call graph. If the derived class implements this method, it should
43 /// always explicitly call the implementation here.
44 void Inliner::getAnalysisUsage(AnalysisUsage &Info) const {
45 Info.addRequired<TargetData>();
46 CallGraphSCCPass::getAnalysisUsage(Info);
49 // InlineCallIfPossible - If it is possible to inline the specified call site,
50 // do so and update the CallGraph for this operation.
51 static bool InlineCallIfPossible(CallSite CS, CallGraph &CG,
52 const std::set<Function*> &SCCFunctions,
53 const TargetData &TD) {
54 Function *Callee = CS.getCalledFunction();
55 if (!InlineFunction(CS, &CG, &TD)) return false;
57 // If we inlined the last possible call site to the function, delete the
59 if (Callee->use_empty() && Callee->hasInternalLinkage() &&
60 !SCCFunctions.count(Callee)) {
61 DOUT << " -> Deleting dead function: " << Callee->getName() << "\n";
63 // Remove any call graph edges from the callee to its callees.
64 CallGraphNode *CalleeNode = CG[Callee];
65 while (CalleeNode->begin() != CalleeNode->end())
66 CalleeNode->removeCallEdgeTo((CalleeNode->end()-1)->second);
68 // Removing the node for callee from the call graph and delete it.
69 delete CG.removeFunctionFromModule(CalleeNode);
75 bool Inliner::runOnSCC(const std::vector<CallGraphNode*> &SCC) {
76 CallGraph &CG = getAnalysis<CallGraph>();
78 std::set<Function*> SCCFunctions;
79 DOUT << "Inliner visiting SCC:";
80 for (unsigned i = 0, e = SCC.size(); i != e; ++i) {
81 Function *F = SCC[i]->getFunction();
82 if (F) SCCFunctions.insert(F);
83 DOUT << " " << (F ? F->getName() : "INDIRECTNODE");
86 // Scan through and identify all call sites ahead of time so that we only
87 // inline call sites in the original functions, not call sites that result
88 // from inlining other functions.
89 std::vector<CallSite> CallSites;
91 for (unsigned i = 0, e = SCC.size(); i != e; ++i)
92 if (Function *F = SCC[i]->getFunction())
93 for (Function::iterator BB = F->begin(), E = F->end(); BB != E; ++BB)
94 for (BasicBlock::iterator I = BB->begin(); I != BB->end(); ++I) {
95 CallSite CS = CallSite::get(I);
96 if (CS.getInstruction() && (!CS.getCalledFunction() ||
97 !CS.getCalledFunction()->isDeclaration()))
98 CallSites.push_back(CS);
101 DOUT << ": " << CallSites.size() << " call sites.\n";
103 // Now that we have all of the call sites, move the ones to functions in the
104 // current SCC to the end of the list.
105 unsigned FirstCallInSCC = CallSites.size();
106 for (unsigned i = 0; i < FirstCallInSCC; ++i)
107 if (Function *F = CallSites[i].getCalledFunction())
108 if (SCCFunctions.count(F))
109 std::swap(CallSites[i--], CallSites[--FirstCallInSCC]);
111 // Now that we have all of the call sites, loop over them and inline them if
112 // it looks profitable to do so.
113 bool Changed = false;
117 // Iterate over the outer loop because inlining functions can cause indirect
118 // calls to become direct calls.
119 for (unsigned CSi = 0; CSi != CallSites.size(); ++CSi)
120 if (Function *Callee = CallSites[CSi].getCalledFunction()) {
121 // Calls to external functions are never inlinable.
122 if (Callee->isDeclaration() ||
123 CallSites[CSi].getInstruction()->getParent()->getParent() ==Callee){
124 if (SCC.size() == 1) {
125 std::swap(CallSites[CSi], CallSites.back());
126 CallSites.pop_back();
128 // Keep the 'in SCC / not in SCC' boundary correct.
129 CallSites.erase(CallSites.begin()+CSi);
135 // If the policy determines that we should inline this function,
137 CallSite CS = CallSites[CSi];
138 int InlineCost = getInlineCost(CS);
139 if (InlineCost >= (int)InlineThreshold) {
140 DOUT << " NOT Inlining: cost=" << InlineCost
141 << ", Call: " << *CS.getInstruction();
143 DOUT << " Inlining: cost=" << InlineCost
144 << ", Call: " << *CS.getInstruction();
146 // Attempt to inline the function...
147 if (InlineCallIfPossible(CS, CG, SCCFunctions,
148 getAnalysis<TargetData>())) {
149 // Remove this call site from the list. If possible, use
150 // swap/pop_back for efficiency, but do not use it if doing so would
151 // move a call site to a function in this SCC before the
152 // 'FirstCallInSCC' barrier.
153 if (SCC.size() == 1) {
154 std::swap(CallSites[CSi], CallSites.back());
155 CallSites.pop_back();
157 CallSites.erase(CallSites.begin()+CSi);
167 } while (LocalChange);
172 // doFinalization - Remove now-dead linkonce functions at the end of
173 // processing to avoid breaking the SCC traversal.
174 bool Inliner::doFinalization(CallGraph &CG) {
175 std::set<CallGraphNode*> FunctionsToRemove;
177 // Scan for all of the functions, looking for ones that should now be removed
178 // from the program. Insert the dead ones in the FunctionsToRemove set.
179 for (CallGraph::iterator I = CG.begin(), E = CG.end(); I != E; ++I) {
180 CallGraphNode *CGN = I->second;
181 if (Function *F = CGN ? CGN->getFunction() : 0) {
182 // If the only remaining users of the function are dead constants, remove
184 F->removeDeadConstantUsers();
186 if ((F->hasLinkOnceLinkage() || F->hasInternalLinkage()) &&
189 // Remove any call graph edges from the function to its callees.
190 while (CGN->begin() != CGN->end())
191 CGN->removeCallEdgeTo((CGN->end()-1)->second);
193 // Remove any edges from the external node to the function's call graph
194 // node. These edges might have been made irrelegant due to
195 // optimization of the program.
196 CG.getExternalCallingNode()->removeAnyCallEdgeTo(CGN);
198 // Removing the node for callee from the call graph and delete it.
199 FunctionsToRemove.insert(CGN);
204 // Now that we know which functions to delete, do so. We didn't want to do
205 // this inline, because that would invalidate our CallGraph::iterator
207 bool Changed = false;
208 for (std::set<CallGraphNode*>::iterator I = FunctionsToRemove.begin(),
209 E = FunctionsToRemove.end(); I != E; ++I) {
210 delete CG.removeFunctionFromModule(*I);