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 InlineLimit("inline-threshold", cl::Hidden, cl::init(200),
35 cl::desc("Control the amount of inlining to perform (default = 200)"));
37 Inliner::Inliner(void *ID)
38 : CallGraphSCCPass(ID), InlineThreshold(InlineLimit) {}
40 Inliner::Inliner(void *ID, int Threshold)
41 : CallGraphSCCPass(ID), InlineThreshold(Threshold) {}
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";
64 CallGraphNode *CalleeNode = CG[Callee];
66 // Remove any call graph edges from the callee to its callees.
67 CalleeNode->removeAllCalledFunctions();
69 // Removing the node for callee from the call graph and delete it.
70 delete CG.removeFunctionFromModule(CalleeNode);
76 /// shouldInline - Return true if the inliner should attempt to inline
77 /// at the given CallSite.
78 bool Inliner::shouldInline(CallSite CS) {
79 InlineCost IC = getInlineCost(CS);
80 float FudgeFactor = getInlineFudgeFactor(CS);
83 DOUT << " Inlining: cost=always"
84 << ", Call: " << *CS.getInstruction();
89 DOUT << " NOT Inlining: cost=never"
90 << ", Call: " << *CS.getInstruction();
94 int Cost = IC.getValue();
95 int CurrentThreshold = InlineThreshold;
96 Function *Fn = CS.getCaller();
97 if (Fn && !Fn->isDeclaration()
98 && Fn->hasFnAttr(Attribute::OptimizeForSize)
99 && InlineThreshold != 50) {
100 CurrentThreshold = 50;
103 if (Cost >= (int)(CurrentThreshold * FudgeFactor)) {
104 DOUT << " NOT Inlining: cost=" << Cost
105 << ", Call: " << *CS.getInstruction();
108 DOUT << " Inlining: cost=" << Cost
109 << ", Call: " << *CS.getInstruction();
114 bool Inliner::runOnSCC(const std::vector<CallGraphNode*> &SCC) {
115 CallGraph &CG = getAnalysis<CallGraph>();
117 std::set<Function*> SCCFunctions;
118 DOUT << "Inliner visiting SCC:";
119 for (unsigned i = 0, e = SCC.size(); i != e; ++i) {
120 Function *F = SCC[i]->getFunction();
121 if (F) SCCFunctions.insert(F);
122 DOUT << " " << (F ? F->getName() : "INDIRECTNODE");
125 // Scan through and identify all call sites ahead of time so that we only
126 // inline call sites in the original functions, not call sites that result
127 // from inlining other functions.
128 std::vector<CallSite> CallSites;
130 for (unsigned i = 0, e = SCC.size(); i != e; ++i)
131 if (Function *F = SCC[i]->getFunction())
132 for (Function::iterator BB = F->begin(), E = F->end(); BB != E; ++BB)
133 for (BasicBlock::iterator I = BB->begin(); I != BB->end(); ++I) {
134 CallSite CS = CallSite::get(I);
135 if (CS.getInstruction() && (!CS.getCalledFunction() ||
136 !CS.getCalledFunction()->isDeclaration()))
137 CallSites.push_back(CS);
140 DOUT << ": " << CallSites.size() << " call sites.\n";
142 // Now that we have all of the call sites, move the ones to functions in the
143 // current SCC to the end of the list.
144 unsigned FirstCallInSCC = CallSites.size();
145 for (unsigned i = 0; i < FirstCallInSCC; ++i)
146 if (Function *F = CallSites[i].getCalledFunction())
147 if (SCCFunctions.count(F))
148 std::swap(CallSites[i--], CallSites[--FirstCallInSCC]);
150 // Now that we have all of the call sites, loop over them and inline them if
151 // it looks profitable to do so.
152 bool Changed = false;
156 // Iterate over the outer loop because inlining functions can cause indirect
157 // calls to become direct calls.
158 for (unsigned CSi = 0; CSi != CallSites.size(); ++CSi)
159 if (Function *Callee = CallSites[CSi].getCalledFunction()) {
160 // Calls to external functions are never inlinable.
161 if (Callee->isDeclaration() ||
162 CallSites[CSi].getInstruction()->getParent()->getParent() ==Callee){
163 if (SCC.size() == 1) {
164 std::swap(CallSites[CSi], CallSites.back());
165 CallSites.pop_back();
167 // Keep the 'in SCC / not in SCC' boundary correct.
168 CallSites.erase(CallSites.begin()+CSi);
174 // If the policy determines that we should inline this function,
176 CallSite CS = CallSites[CSi];
177 if (shouldInline(CS)) {
178 // Attempt to inline the function...
179 if (InlineCallIfPossible(CS, CG, SCCFunctions,
180 getAnalysis<TargetData>())) {
181 // Remove this call site from the list. If possible, use
182 // swap/pop_back for efficiency, but do not use it if doing so would
183 // move a call site to a function in this SCC before the
184 // 'FirstCallInSCC' barrier.
185 if (SCC.size() == 1) {
186 std::swap(CallSites[CSi], CallSites.back());
187 CallSites.pop_back();
189 CallSites.erase(CallSites.begin()+CSi);
199 } while (LocalChange);
204 // doFinalization - Remove now-dead linkonce functions at the end of
205 // processing to avoid breaking the SCC traversal.
206 bool Inliner::doFinalization(CallGraph &CG) {
207 std::set<CallGraphNode*> FunctionsToRemove;
209 // Scan for all of the functions, looking for ones that should now be removed
210 // from the program. Insert the dead ones in the FunctionsToRemove set.
211 for (CallGraph::iterator I = CG.begin(), E = CG.end(); I != E; ++I) {
212 CallGraphNode *CGN = I->second;
213 if (Function *F = CGN ? CGN->getFunction() : 0) {
214 // If the only remaining users of the function are dead constants, remove
216 F->removeDeadConstantUsers();
218 if ((F->hasLinkOnceLinkage() || F->hasInternalLinkage()) &&
221 // Remove any call graph edges from the function to its callees.
222 CGN->removeAllCalledFunctions();
224 // Remove any edges from the external node to the function's call graph
225 // node. These edges might have been made irrelegant due to
226 // optimization of the program.
227 CG.getExternalCallingNode()->removeAnyCallEdgeTo(CGN);
229 // Removing the node for callee from the call graph and delete it.
230 FunctionsToRemove.insert(CGN);
235 // Now that we know which functions to delete, do so. We didn't want to do
236 // this inline, because that would invalidate our CallGraph::iterator
238 bool Changed = false;
239 for (std::set<CallGraphNode*>::iterator I = FunctionsToRemove.begin(),
240 E = FunctionsToRemove.end(); I != E; ++I) {
241 delete CG.removeFunctionFromModule(*I);