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 the inlined function had a higher stack protection level than the
60 // calling function, then bump up the caller's stack protection level.
61 Function *Caller = CS.getCaller();
62 if (Callee->hasFnAttr(Attribute::StackProtectReq))
63 Caller->addFnAttr(Attribute::StackProtectReq);
64 else if (Callee->hasFnAttr(Attribute::StackProtect) &&
65 !Caller->hasFnAttr(Attribute::StackProtectReq))
66 Caller->addFnAttr(Attribute::StackProtect);
68 // If we inlined the last possible call site to the function, delete the
70 if (Callee->use_empty() && Callee->hasInternalLinkage() &&
71 !SCCFunctions.count(Callee)) {
72 DOUT << " -> Deleting dead function: " << Callee->getName() << "\n";
73 CallGraphNode *CalleeNode = CG[Callee];
75 // Remove any call graph edges from the callee to its callees.
76 CalleeNode->removeAllCalledFunctions();
78 // Removing the node for callee from the call graph and delete it.
79 delete CG.removeFunctionFromModule(CalleeNode);
85 /// shouldInline - Return true if the inliner should attempt to inline
86 /// at the given CallSite.
87 bool Inliner::shouldInline(CallSite CS) {
88 InlineCost IC = getInlineCost(CS);
89 float FudgeFactor = getInlineFudgeFactor(CS);
92 DOUT << " Inlining: cost=always"
93 << ", Call: " << *CS.getInstruction();
98 DOUT << " NOT Inlining: cost=never"
99 << ", Call: " << *CS.getInstruction();
103 int Cost = IC.getValue();
104 int CurrentThreshold = InlineThreshold;
105 Function *Fn = CS.getCaller();
106 if (Fn && !Fn->isDeclaration()
107 && Fn->hasFnAttr(Attribute::OptimizeForSize)
108 && InlineThreshold != 50) {
109 CurrentThreshold = 50;
112 if (Cost >= (int)(CurrentThreshold * FudgeFactor)) {
113 DOUT << " NOT Inlining: cost=" << Cost
114 << ", Call: " << *CS.getInstruction();
117 DOUT << " Inlining: cost=" << Cost
118 << ", Call: " << *CS.getInstruction();
123 bool Inliner::runOnSCC(const std::vector<CallGraphNode*> &SCC) {
124 CallGraph &CG = getAnalysis<CallGraph>();
126 std::set<Function*> SCCFunctions;
127 DOUT << "Inliner visiting SCC:";
128 for (unsigned i = 0, e = SCC.size(); i != e; ++i) {
129 Function *F = SCC[i]->getFunction();
130 if (F) SCCFunctions.insert(F);
131 DOUT << " " << (F ? F->getName() : "INDIRECTNODE");
134 // Scan through and identify all call sites ahead of time so that we only
135 // inline call sites in the original functions, not call sites that result
136 // from inlining other functions.
137 std::vector<CallSite> CallSites;
139 for (unsigned i = 0, e = SCC.size(); i != e; ++i)
140 if (Function *F = SCC[i]->getFunction())
141 for (Function::iterator BB = F->begin(), E = F->end(); BB != E; ++BB)
142 for (BasicBlock::iterator I = BB->begin(); I != BB->end(); ++I) {
143 CallSite CS = CallSite::get(I);
144 if (CS.getInstruction() && (!CS.getCalledFunction() ||
145 !CS.getCalledFunction()->isDeclaration()))
146 CallSites.push_back(CS);
149 DOUT << ": " << CallSites.size() << " call sites.\n";
151 // Now that we have all of the call sites, move the ones to functions in the
152 // current SCC to the end of the list.
153 unsigned FirstCallInSCC = CallSites.size();
154 for (unsigned i = 0; i < FirstCallInSCC; ++i)
155 if (Function *F = CallSites[i].getCalledFunction())
156 if (SCCFunctions.count(F))
157 std::swap(CallSites[i--], CallSites[--FirstCallInSCC]);
159 // Now that we have all of the call sites, loop over them and inline them if
160 // it looks profitable to do so.
161 bool Changed = false;
165 // Iterate over the outer loop because inlining functions can cause indirect
166 // calls to become direct calls.
167 for (unsigned CSi = 0; CSi != CallSites.size(); ++CSi)
168 if (Function *Callee = CallSites[CSi].getCalledFunction()) {
169 // Calls to external functions are never inlinable.
170 if (Callee->isDeclaration() ||
171 CallSites[CSi].getInstruction()->getParent()->getParent() ==Callee){
172 if (SCC.size() == 1) {
173 std::swap(CallSites[CSi], CallSites.back());
174 CallSites.pop_back();
176 // Keep the 'in SCC / not in SCC' boundary correct.
177 CallSites.erase(CallSites.begin()+CSi);
183 // If the policy determines that we should inline this function,
185 CallSite CS = CallSites[CSi];
186 if (shouldInline(CS)) {
187 // Attempt to inline the function...
188 if (InlineCallIfPossible(CS, CG, SCCFunctions,
189 getAnalysis<TargetData>())) {
190 // Remove this call site from the list. If possible, use
191 // swap/pop_back for efficiency, but do not use it if doing so would
192 // move a call site to a function in this SCC before the
193 // 'FirstCallInSCC' barrier.
194 if (SCC.size() == 1) {
195 std::swap(CallSites[CSi], CallSites.back());
196 CallSites.pop_back();
198 CallSites.erase(CallSites.begin()+CSi);
208 } while (LocalChange);
213 // doFinalization - Remove now-dead linkonce functions at the end of
214 // processing to avoid breaking the SCC traversal.
215 bool Inliner::doFinalization(CallGraph &CG) {
216 return removeDeadFunctions(CG);
219 /// removeDeadFunctions - Remove dead functions that are not included in
220 /// DNR (Do Not Remove) list.
221 bool Inliner::removeDeadFunctions(CallGraph &CG,
222 SmallPtrSet<const Function *, 16> *DNR) {
223 std::set<CallGraphNode*> FunctionsToRemove;
225 // Scan for all of the functions, looking for ones that should now be removed
226 // from the program. Insert the dead ones in the FunctionsToRemove set.
227 for (CallGraph::iterator I = CG.begin(), E = CG.end(); I != E; ++I) {
228 CallGraphNode *CGN = I->second;
229 if (Function *F = CGN ? CGN->getFunction() : 0) {
230 // If the only remaining users of the function are dead constants, remove
232 F->removeDeadConstantUsers();
234 if (DNR && DNR->count(F))
237 if ((F->hasLinkOnceLinkage() || F->hasInternalLinkage()) &&
240 // Remove any call graph edges from the function to its callees.
241 CGN->removeAllCalledFunctions();
243 // Remove any edges from the external node to the function's call graph
244 // node. These edges might have been made irrelegant due to
245 // optimization of the program.
246 CG.getExternalCallingNode()->removeAnyCallEdgeTo(CGN);
248 // Removing the node for callee from the call graph and delete it.
249 FunctionsToRemove.insert(CGN);
254 // Now that we know which functions to delete, do so. We didn't want to do
255 // this inline, because that would invalidate our CallGraph::iterator
257 bool Changed = false;
258 for (std::set<CallGraphNode*>::iterator I = FunctionsToRemove.begin(),
259 E = FunctionsToRemove.end(); I != E; ++I) {
260 delete CG.removeFunctionFromModule(*I);