1 //===- Inliner.cpp - Code common to all inliners --------------------------===//
3 // The LLVM Compiler Infrastructure
5 // This file is distributed under the University of Illinois Open Source
6 // 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<int> // 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 Inliner::Inliner(const void *ID, int Threshold)
43 : CallGraphSCCPass((intptr_t)ID), InlineThreshold(Threshold) {}
45 /// getAnalysisUsage - For this class, we declare that we require and preserve
46 /// the call graph. If the derived class implements this method, it should
47 /// always explicitly call the implementation here.
48 void Inliner::getAnalysisUsage(AnalysisUsage &Info) const {
49 Info.addRequired<TargetData>();
50 CallGraphSCCPass::getAnalysisUsage(Info);
53 // InlineCallIfPossible - If it is possible to inline the specified call site,
54 // do so and update the CallGraph for this operation.
55 static bool InlineCallIfPossible(CallSite CS, CallGraph &CG,
56 const std::set<Function*> &SCCFunctions,
57 const TargetData &TD) {
58 Function *Callee = CS.getCalledFunction();
59 if (!InlineFunction(CS, &CG, &TD)) return false;
61 // If we inlined the last possible call site to the function, delete the
63 if (Callee->use_empty() && Callee->hasInternalLinkage() &&
64 !SCCFunctions.count(Callee)) {
65 DOUT << " -> Deleting dead function: " << Callee->getName() << "\n";
67 // Remove any call graph edges from the callee to its callees.
68 CallGraphNode *CalleeNode = CG[Callee];
69 while (!CalleeNode->empty())
70 CalleeNode->removeCallEdgeTo((CalleeNode->end()-1)->second);
72 // Removing the node for callee from the call graph and delete it.
73 delete CG.removeFunctionFromModule(CalleeNode);
79 bool Inliner::runOnSCC(const std::vector<CallGraphNode*> &SCC) {
80 CallGraph &CG = getAnalysis<CallGraph>();
82 std::set<Function*> SCCFunctions;
83 DOUT << "Inliner visiting SCC:";
84 for (unsigned i = 0, e = SCC.size(); i != e; ++i) {
85 Function *F = SCC[i]->getFunction();
86 if (F) SCCFunctions.insert(F);
87 DOUT << " " << (F ? F->getName() : "INDIRECTNODE");
90 // Scan through and identify all call sites ahead of time so that we only
91 // inline call sites in the original functions, not call sites that result
92 // from inlining other functions.
93 std::vector<CallSite> CallSites;
95 for (unsigned i = 0, e = SCC.size(); i != e; ++i)
96 if (Function *F = SCC[i]->getFunction())
97 for (Function::iterator BB = F->begin(), E = F->end(); BB != E; ++BB)
98 for (BasicBlock::iterator I = BB->begin(); I != BB->end(); ++I) {
99 CallSite CS = CallSite::get(I);
100 if (CS.getInstruction() && (!CS.getCalledFunction() ||
101 !CS.getCalledFunction()->isDeclaration()))
102 CallSites.push_back(CS);
105 DOUT << ": " << CallSites.size() << " call sites.\n";
107 // Now that we have all of the call sites, move the ones to functions in the
108 // current SCC to the end of the list.
109 unsigned FirstCallInSCC = CallSites.size();
110 for (unsigned i = 0; i < FirstCallInSCC; ++i)
111 if (Function *F = CallSites[i].getCalledFunction())
112 if (SCCFunctions.count(F))
113 std::swap(CallSites[i--], CallSites[--FirstCallInSCC]);
115 // Now that we have all of the call sites, loop over them and inline them if
116 // it looks profitable to do so.
117 bool Changed = false;
121 // Iterate over the outer loop because inlining functions can cause indirect
122 // calls to become direct calls.
123 for (unsigned CSi = 0; CSi != CallSites.size(); ++CSi)
124 if (Function *Callee = CallSites[CSi].getCalledFunction()) {
125 // Calls to external functions are never inlinable.
126 if (Callee->isDeclaration() ||
127 CallSites[CSi].getInstruction()->getParent()->getParent() ==Callee){
128 if (SCC.size() == 1) {
129 std::swap(CallSites[CSi], CallSites.back());
130 CallSites.pop_back();
132 // Keep the 'in SCC / not in SCC' boundary correct.
133 CallSites.erase(CallSites.begin()+CSi);
139 // If the policy determines that we should inline this function,
141 CallSite CS = CallSites[CSi];
142 int InlineCost = getInlineCost(CS);
143 if (InlineCost >= (int)InlineThreshold) {
144 DOUT << " NOT Inlining: cost=" << InlineCost
145 << ", Call: " << *CS.getInstruction();
147 DOUT << " Inlining: cost=" << InlineCost
148 << ", Call: " << *CS.getInstruction();
150 // Attempt to inline the function...
151 if (InlineCallIfPossible(CS, CG, SCCFunctions,
152 getAnalysis<TargetData>())) {
153 // Remove this call site from the list. If possible, use
154 // swap/pop_back for efficiency, but do not use it if doing so would
155 // move a call site to a function in this SCC before the
156 // 'FirstCallInSCC' barrier.
157 if (SCC.size() == 1) {
158 std::swap(CallSites[CSi], CallSites.back());
159 CallSites.pop_back();
161 CallSites.erase(CallSites.begin()+CSi);
171 } while (LocalChange);
176 // doFinalization - Remove now-dead linkonce functions at the end of
177 // processing to avoid breaking the SCC traversal.
178 bool Inliner::doFinalization(CallGraph &CG) {
179 std::set<CallGraphNode*> FunctionsToRemove;
181 // Scan for all of the functions, looking for ones that should now be removed
182 // from the program. Insert the dead ones in the FunctionsToRemove set.
183 for (CallGraph::iterator I = CG.begin(), E = CG.end(); I != E; ++I) {
184 CallGraphNode *CGN = I->second;
185 if (Function *F = CGN ? CGN->getFunction() : 0) {
186 // If the only remaining users of the function are dead constants, remove
188 F->removeDeadConstantUsers();
190 if ((F->hasLinkOnceLinkage() || F->hasInternalLinkage()) &&
193 // Remove any call graph edges from the function to its callees.
194 while (!CGN->empty())
195 CGN->removeCallEdgeTo((CGN->end()-1)->second);
197 // Remove any edges from the external node to the function's call graph
198 // node. These edges might have been made irrelegant due to
199 // optimization of the program.
200 CG.getExternalCallingNode()->removeAnyCallEdgeTo(CGN);
202 // Removing the node for callee from the call graph and delete it.
203 FunctionsToRemove.insert(CGN);
208 // Now that we know which functions to delete, do so. We didn't want to do
209 // this inline, because that would invalidate our CallGraph::iterator
211 bool Changed = false;
212 for (std::set<CallGraphNode*>::iterator I = FunctionsToRemove.begin(),
213 E = FunctionsToRemove.end(); I != E; ++I) {
214 delete CG.removeFunctionFromModule(*I);