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/IntrinsicInst.h"
20 #include "llvm/Analysis/CallGraph.h"
21 #include "llvm/Support/CallSite.h"
22 #include "llvm/Target/TargetData.h"
23 #include "llvm/Transforms/IPO/InlinerPass.h"
24 #include "llvm/Transforms/Utils/Cloning.h"
25 #include "llvm/Support/CommandLine.h"
26 #include "llvm/Support/Debug.h"
27 #include "llvm/ADT/Statistic.h"
31 STATISTIC(NumInlined, "Number of functions inlined");
32 STATISTIC(NumDeleted, "Number of functions deleted because all callers found");
35 InlineLimit("inline-threshold", cl::Hidden, cl::init(200),
36 cl::desc("Control the amount of inlining to perform (default = 200)"));
38 Inliner::Inliner(void *ID)
39 : CallGraphSCCPass(ID), InlineThreshold(InlineLimit) {}
41 Inliner::Inliner(void *ID, int Threshold)
42 : CallGraphSCCPass(ID), InlineThreshold(Threshold) {}
44 /// getAnalysisUsage - For this class, we declare that we require and preserve
45 /// the call graph. If the derived class implements this method, it should
46 /// always explicitly call the implementation here.
47 void Inliner::getAnalysisUsage(AnalysisUsage &Info) const {
48 Info.addRequired<TargetData>();
49 CallGraphSCCPass::getAnalysisUsage(Info);
52 // InlineCallIfPossible - If it is possible to inline the specified call site,
53 // do so and update the CallGraph for this operation.
54 bool Inliner::InlineCallIfPossible(CallSite CS, CallGraph &CG,
55 const SmallPtrSet<Function*, 8> &SCCFunctions,
56 const TargetData &TD) {
57 Function *Callee = CS.getCalledFunction();
58 Function *Caller = CS.getCaller();
60 if (!InlineFunction(CS, &CG, &TD)) return false;
62 // If the inlined function had a higher stack protection level than the
63 // calling function, then bump up the caller's stack protection level.
64 if (Callee->hasFnAttr(Attribute::StackProtectReq))
65 Caller->addFnAttr(Attribute::StackProtectReq);
66 else if (Callee->hasFnAttr(Attribute::StackProtect) &&
67 !Caller->hasFnAttr(Attribute::StackProtectReq))
68 Caller->addFnAttr(Attribute::StackProtect);
70 // If we inlined the last possible call site to the function, delete the
72 if (Callee->use_empty() && (Callee->hasLocalLinkage() ||
73 Callee->hasAvailableExternallyLinkage()) &&
74 !SCCFunctions.count(Callee)) {
75 DOUT << " -> Deleting dead function: " << Callee->getName() << "\n";
76 CallGraphNode *CalleeNode = CG[Callee];
78 // Remove any call graph edges from the callee to its callees.
79 CalleeNode->removeAllCalledFunctions();
81 resetCachedCostInfo(CalleeNode->getFunction());
83 // Removing the node for callee from the call graph and delete it.
84 delete CG.removeFunctionFromModule(CalleeNode);
90 /// shouldInline - Return true if the inliner should attempt to inline
91 /// at the given CallSite.
92 bool Inliner::shouldInline(CallSite CS) {
93 InlineCost IC = getInlineCost(CS);
94 float FudgeFactor = getInlineFudgeFactor(CS);
97 DOUT << " Inlining: cost=always"
98 << ", Call: " << *CS.getInstruction() << "\n";
103 DOUT << " NOT Inlining: cost=never"
104 << ", Call: " << *CS.getInstruction() << "\n";
108 int Cost = IC.getValue();
109 int CurrentThreshold = InlineThreshold;
110 Function *Fn = CS.getCaller();
111 if (Fn && !Fn->isDeclaration()
112 && Fn->hasFnAttr(Attribute::OptimizeForSize)
113 && InlineThreshold != 50) {
114 CurrentThreshold = 50;
117 if (Cost >= (int)(CurrentThreshold * FudgeFactor)) {
118 DOUT << " NOT Inlining: cost=" << Cost
119 << ", Call: " << *CS.getInstruction() << "\n";
122 DOUT << " Inlining: cost=" << Cost
123 << ", Call: " << *CS.getInstruction() << "\n";
128 bool Inliner::runOnSCC(const std::vector<CallGraphNode*> &SCC) {
129 CallGraph &CG = getAnalysis<CallGraph>();
130 TargetData &TD = getAnalysis<TargetData>();
132 SmallPtrSet<Function*, 8> SCCFunctions;
133 DOUT << "Inliner visiting SCC:";
134 for (unsigned i = 0, e = SCC.size(); i != e; ++i) {
135 Function *F = SCC[i]->getFunction();
136 if (F) SCCFunctions.insert(F);
137 DOUT << " " << (F ? F->getName() : "INDIRECTNODE");
140 // Scan through and identify all call sites ahead of time so that we only
141 // inline call sites in the original functions, not call sites that result
142 // from inlining other functions.
143 std::vector<CallSite> CallSites;
145 for (unsigned i = 0, e = SCC.size(); i != e; ++i)
146 if (Function *F = SCC[i]->getFunction())
147 for (Function::iterator BB = F->begin(), E = F->end(); BB != E; ++BB)
148 for (BasicBlock::iterator I = BB->begin(); I != BB->end(); ++I) {
149 CallSite CS = CallSite::get(I);
150 if (CS.getInstruction() && !isa<DbgInfoIntrinsic>(I) &&
151 (!CS.getCalledFunction() ||
152 !CS.getCalledFunction()->isDeclaration()))
153 CallSites.push_back(CS);
156 DOUT << ": " << CallSites.size() << " call sites.\n";
158 // Now that we have all of the call sites, move the ones to functions in the
159 // current SCC to the end of the list.
160 unsigned FirstCallInSCC = CallSites.size();
161 for (unsigned i = 0; i < FirstCallInSCC; ++i)
162 if (Function *F = CallSites[i].getCalledFunction())
163 if (SCCFunctions.count(F))
164 std::swap(CallSites[i--], CallSites[--FirstCallInSCC]);
166 // Now that we have all of the call sites, loop over them and inline them if
167 // it looks profitable to do so.
168 bool Changed = false;
172 // Iterate over the outer loop because inlining functions can cause indirect
173 // calls to become direct calls.
174 for (unsigned CSi = 0; CSi != CallSites.size(); ++CSi)
175 if (Function *Callee = CallSites[CSi].getCalledFunction()) {
176 // Calls to external functions are never inlinable.
177 if (Callee->isDeclaration()) {
178 if (SCC.size() == 1) {
179 std::swap(CallSites[CSi], CallSites.back());
180 CallSites.pop_back();
182 // Keep the 'in SCC / not in SCC' boundary correct.
183 CallSites.erase(CallSites.begin()+CSi);
189 // If the policy determines that we should inline this function,
191 CallSite CS = CallSites[CSi];
192 if (shouldInline(CS)) {
193 Function *Caller = CS.getCaller();
194 // Attempt to inline the function...
195 if (InlineCallIfPossible(CS, CG, SCCFunctions, TD)) {
196 // Remove any cached cost info for this caller, as inlining the
197 // callee has increased the size of the caller (which may be the
198 // same as the callee).
199 resetCachedCostInfo(Caller);
201 // Remove this call site from the list. If possible, use
202 // swap/pop_back for efficiency, but do not use it if doing so would
203 // move a call site to a function in this SCC before the
204 // 'FirstCallInSCC' barrier.
205 if (SCC.size() == 1) {
206 std::swap(CallSites[CSi], CallSites.back());
207 CallSites.pop_back();
209 CallSites.erase(CallSites.begin()+CSi);
219 } while (LocalChange);
224 // doFinalization - Remove now-dead linkonce functions at the end of
225 // processing to avoid breaking the SCC traversal.
226 bool Inliner::doFinalization(CallGraph &CG) {
227 return removeDeadFunctions(CG);
230 /// removeDeadFunctions - Remove dead functions that are not included in
231 /// DNR (Do Not Remove) list.
232 bool Inliner::removeDeadFunctions(CallGraph &CG,
233 SmallPtrSet<const Function *, 16> *DNR) {
234 std::set<CallGraphNode*> FunctionsToRemove;
236 // Scan for all of the functions, looking for ones that should now be removed
237 // from the program. Insert the dead ones in the FunctionsToRemove set.
238 for (CallGraph::iterator I = CG.begin(), E = CG.end(); I != E; ++I) {
239 CallGraphNode *CGN = I->second;
240 if (Function *F = CGN ? CGN->getFunction() : 0) {
241 // If the only remaining users of the function are dead constants, remove
243 F->removeDeadConstantUsers();
245 if (DNR && DNR->count(F))
248 if ((F->hasLinkOnceLinkage() || F->hasLocalLinkage()) &&
251 // Remove any call graph edges from the function to its callees.
252 CGN->removeAllCalledFunctions();
254 // Remove any edges from the external node to the function's call graph
255 // node. These edges might have been made irrelegant due to
256 // optimization of the program.
257 CG.getExternalCallingNode()->removeAnyCallEdgeTo(CGN);
259 // Removing the node for callee from the call graph and delete it.
260 FunctionsToRemove.insert(CGN);
265 // Now that we know which functions to delete, do so. We didn't want to do
266 // this inline, because that would invalidate our CallGraph::iterator
268 bool Changed = false;
269 for (std::set<CallGraphNode*>::iterator I = FunctionsToRemove.begin(),
270 E = FunctionsToRemove.end(); I != E; ++I) {
271 resetCachedCostInfo((*I)->getFunction());
272 delete CG.removeFunctionFromModule(*I);