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 const char Inliner::ID = 0;
41 : CallGraphSCCPass((intptr_t)&ID), InlineThreshold(InlineLimit) {}
43 /// getAnalysisUsage - For this class, we declare that we require and preserve
44 /// the call graph. If the derived class implements this method, it should
45 /// always explicitly call the implementation here.
46 void Inliner::getAnalysisUsage(AnalysisUsage &Info) const {
47 Info.addRequired<TargetData>();
48 CallGraphSCCPass::getAnalysisUsage(Info);
51 // InlineCallIfPossible - If it is possible to inline the specified call site,
52 // do so and update the CallGraph for this operation.
53 static bool InlineCallIfPossible(CallSite CS, CallGraph &CG,
54 const std::set<Function*> &SCCFunctions,
55 const TargetData &TD) {
56 Function *Callee = CS.getCalledFunction();
57 if (!InlineFunction(CS, &CG, &TD)) return false;
59 // If we inlined the last possible call site to the function, delete the
61 if (Callee->use_empty() && Callee->hasInternalLinkage() &&
62 !SCCFunctions.count(Callee)) {
63 DOUT << " -> Deleting dead function: " << Callee->getName() << "\n";
65 // Remove any call graph edges from the callee to its callees.
66 CallGraphNode *CalleeNode = CG[Callee];
67 while (CalleeNode->begin() != CalleeNode->end())
68 CalleeNode->removeCallEdgeTo((CalleeNode->end()-1)->second);
70 // Removing the node for callee from the call graph and delete it.
71 delete CG.removeFunctionFromModule(CalleeNode);
77 bool Inliner::runOnSCC(const std::vector<CallGraphNode*> &SCC) {
78 CallGraph &CG = getAnalysis<CallGraph>();
80 std::set<Function*> SCCFunctions;
81 DOUT << "Inliner visiting SCC:";
82 for (unsigned i = 0, e = SCC.size(); i != e; ++i) {
83 Function *F = SCC[i]->getFunction();
84 if (F) SCCFunctions.insert(F);
85 DOUT << " " << (F ? F->getName() : "INDIRECTNODE");
88 // Scan through and identify all call sites ahead of time so that we only
89 // inline call sites in the original functions, not call sites that result
90 // from inlining other functions.
91 std::vector<CallSite> CallSites;
93 for (unsigned i = 0, e = SCC.size(); i != e; ++i)
94 if (Function *F = SCC[i]->getFunction())
95 for (Function::iterator BB = F->begin(), E = F->end(); BB != E; ++BB)
96 for (BasicBlock::iterator I = BB->begin(); I != BB->end(); ++I) {
97 CallSite CS = CallSite::get(I);
98 if (CS.getInstruction() && (!CS.getCalledFunction() ||
99 !CS.getCalledFunction()->isDeclaration()))
100 CallSites.push_back(CS);
103 DOUT << ": " << CallSites.size() << " call sites.\n";
105 // Now that we have all of the call sites, move the ones to functions in the
106 // current SCC to the end of the list.
107 unsigned FirstCallInSCC = CallSites.size();
108 for (unsigned i = 0; i < FirstCallInSCC; ++i)
109 if (Function *F = CallSites[i].getCalledFunction())
110 if (SCCFunctions.count(F))
111 std::swap(CallSites[i--], CallSites[--FirstCallInSCC]);
113 // Now that we have all of the call sites, loop over them and inline them if
114 // it looks profitable to do so.
115 bool Changed = false;
119 // Iterate over the outer loop because inlining functions can cause indirect
120 // calls to become direct calls.
121 for (unsigned CSi = 0; CSi != CallSites.size(); ++CSi)
122 if (Function *Callee = CallSites[CSi].getCalledFunction()) {
123 // Calls to external functions are never inlinable.
124 if (Callee->isDeclaration() ||
125 CallSites[CSi].getInstruction()->getParent()->getParent() ==Callee){
126 if (SCC.size() == 1) {
127 std::swap(CallSites[CSi], CallSites.back());
128 CallSites.pop_back();
130 // Keep the 'in SCC / not in SCC' boundary correct.
131 CallSites.erase(CallSites.begin()+CSi);
137 // If the policy determines that we should inline this function,
139 CallSite CS = CallSites[CSi];
140 int InlineCost = getInlineCost(CS);
141 if (InlineCost >= (int)InlineThreshold) {
142 DOUT << " NOT Inlining: cost=" << InlineCost
143 << ", Call: " << *CS.getInstruction();
145 DOUT << " Inlining: cost=" << InlineCost
146 << ", Call: " << *CS.getInstruction();
148 // Attempt to inline the function...
149 if (InlineCallIfPossible(CS, CG, SCCFunctions,
150 getAnalysis<TargetData>())) {
151 // Remove this call site from the list. If possible, use
152 // swap/pop_back for efficiency, but do not use it if doing so would
153 // move a call site to a function in this SCC before the
154 // 'FirstCallInSCC' barrier.
155 if (SCC.size() == 1) {
156 std::swap(CallSites[CSi], CallSites.back());
157 CallSites.pop_back();
159 CallSites.erase(CallSites.begin()+CSi);
169 } while (LocalChange);
174 // doFinalization - Remove now-dead linkonce functions at the end of
175 // processing to avoid breaking the SCC traversal.
176 bool Inliner::doFinalization(CallGraph &CG) {
177 std::set<CallGraphNode*> FunctionsToRemove;
179 // Scan for all of the functions, looking for ones that should now be removed
180 // from the program. Insert the dead ones in the FunctionsToRemove set.
181 for (CallGraph::iterator I = CG.begin(), E = CG.end(); I != E; ++I) {
182 CallGraphNode *CGN = I->second;
183 if (Function *F = CGN ? CGN->getFunction() : 0) {
184 // If the only remaining users of the function are dead constants, remove
186 F->removeDeadConstantUsers();
188 if ((F->hasLinkOnceLinkage() || F->hasInternalLinkage()) &&
191 // Remove any call graph edges from the function to its callees.
192 while (CGN->begin() != CGN->end())
193 CGN->removeCallEdgeTo((CGN->end()-1)->second);
195 // Remove any edges from the external node to the function's call graph
196 // node. These edges might have been made irrelegant due to
197 // optimization of the program.
198 CG.getExternalCallingNode()->removeAnyCallEdgeTo(CGN);
200 // Removing the node for callee from the call graph and delete it.
201 FunctionsToRemove.insert(CGN);
206 // Now that we know which functions to delete, do so. We didn't want to do
207 // this inline, because that would invalidate our CallGraph::iterator
209 bool Changed = false;
210 for (std::set<CallGraphNode*>::iterator I = FunctionsToRemove.begin(),
211 E = FunctionsToRemove.end(); I != E; ++I) {
212 delete CG.removeFunctionFromModule(*I);