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