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