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/Support/raw_ostream.h"
28 #include "llvm/ADT/Statistic.h"
32 STATISTIC(NumInlined, "Number of functions inlined");
33 STATISTIC(NumDeleted, "Number of functions deleted because all callers found");
36 InlineLimit("inline-threshold", cl::Hidden, cl::init(200), cl::ZeroOrMore,
37 cl::desc("Control the amount of inlining to perform (default = 200)"));
39 Inliner::Inliner(void *ID)
40 : CallGraphSCCPass(ID), InlineThreshold(InlineLimit) {}
42 Inliner::Inliner(void *ID, int Threshold)
43 : CallGraphSCCPass(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 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() &&
73 (Callee->hasLocalLinkage() || Callee->hasAvailableExternallyLinkage()) &&
74 !SCCFunctions.count(Callee)) {
75 DEBUG(errs() << " -> Deleting dead function: "
76 << Callee->getName() << "\n");
77 CallGraphNode *CalleeNode = CG[Callee];
79 // Remove any call graph edges from the callee to its callees.
80 CalleeNode->removeAllCalledFunctions();
82 resetCachedCostInfo(CalleeNode->getFunction());
84 // Removing the node for callee from the call graph and delete it.
85 delete CG.removeFunctionFromModule(CalleeNode);
91 /// shouldInline - Return true if the inliner should attempt to inline
92 /// at the given CallSite.
93 bool Inliner::shouldInline(CallSite CS) {
94 InlineCost IC = getInlineCost(CS);
97 DEBUG(errs() << " Inlining: cost=always"
98 << ", Call: " << *CS.getInstruction() << "\n");
103 DEBUG(errs() << " 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;
116 float FudgeFactor = getInlineFudgeFactor(CS);
117 if (Cost >= (int)(CurrentThreshold * FudgeFactor)) {
118 DEBUG(errs() << " NOT Inlining: cost=" << Cost
119 << ", Call: " << *CS.getInstruction() << "\n");
123 DEBUG(errs() << " Inlining: cost=" << Cost
124 << ", Call: " << *CS.getInstruction() << "\n");
128 bool Inliner::runOnSCC(const std::vector<CallGraphNode*> &SCC) {
129 CallGraph &CG = getAnalysis<CallGraph>();
130 const TargetData *TD = getAnalysisIfAvailable<TargetData>();
132 SmallPtrSet<Function*, 8> SCCFunctions;
133 DEBUG(errs() << "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 DEBUG(errs() << " " << (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 Function *F = SCC[i]->getFunction();
149 for (Function::iterator BB = F->begin(), E = F->end(); BB != E; ++BB)
150 for (BasicBlock::iterator I = BB->begin(), E = BB->end(); I != E; ++I) {
151 CallSite CS = CallSite::get(I);
152 if (CS.getInstruction() == 0 || isa<DbgInfoIntrinsic>(I))
155 if (CS.getCalledFunction() == 0 ||
156 !CS.getCalledFunction()->isDeclaration())
157 CallSites.push_back(CS);
161 DEBUG(errs() << ": " << CallSites.size() << " call sites.\n");
163 // Now that we have all of the call sites, move the ones to functions in the
164 // current SCC to the end of the list.
165 unsigned FirstCallInSCC = CallSites.size();
166 for (unsigned i = 0; i < FirstCallInSCC; ++i)
167 if (Function *F = CallSites[i].getCalledFunction())
168 if (SCCFunctions.count(F))
169 std::swap(CallSites[i--], CallSites[--FirstCallInSCC]);
171 // Now that we have all of the call sites, loop over them and inline them if
172 // it looks profitable to do so.
173 bool Changed = false;
177 // Iterate over the outer loop because inlining functions can cause indirect
178 // calls to become direct calls.
179 for (unsigned CSi = 0; CSi != CallSites.size(); ++CSi) {
180 // We can only inline direct calls.
181 Function *Callee = CallSites[CSi].getCalledFunction();
182 if (!Callee) continue;
184 // Calls to external functions are never inlinable.
185 if (Callee->isDeclaration()) {
186 if (SCC.size() == 1) {
187 std::swap(CallSites[CSi], CallSites.back());
188 CallSites.pop_back();
190 // Keep the 'in SCC / not in SCC' boundary correct.
191 CallSites.erase(CallSites.begin()+CSi);
197 // If the policy determines that we should inline this function,
199 CallSite CS = CallSites[CSi];
200 if (!shouldInline(CS))
203 Function *Caller = CS.getCaller();
204 // Attempt to inline the function...
205 if (!InlineCallIfPossible(CS, CG, SCCFunctions, TD))
208 // Remove any cached cost info for this caller, as inlining the
209 // callee has increased the size of the caller (which may be the
210 // same as the callee).
211 resetCachedCostInfo(Caller);
213 // Remove this call site from the list. If possible, use
214 // swap/pop_back for efficiency, but do not use it if doing so would
215 // move a call site to a function in this SCC before the
216 // 'FirstCallInSCC' barrier.
217 if (SCC.size() == 1) {
218 std::swap(CallSites[CSi], CallSites.back());
219 CallSites.pop_back();
221 CallSites.erase(CallSites.begin()+CSi);
229 } while (LocalChange);
234 // doFinalization - Remove now-dead linkonce functions at the end of
235 // processing to avoid breaking the SCC traversal.
236 bool Inliner::doFinalization(CallGraph &CG) {
237 return removeDeadFunctions(CG);
240 /// removeDeadFunctions - Remove dead functions that are not included in
241 /// DNR (Do Not Remove) list.
242 bool Inliner::removeDeadFunctions(CallGraph &CG,
243 SmallPtrSet<const Function *, 16> *DNR) {
244 SmallPtrSet<CallGraphNode*, 16> FunctionsToRemove;
246 // Scan for all of the functions, looking for ones that should now be removed
247 // from the program. Insert the dead ones in the FunctionsToRemove set.
248 for (CallGraph::iterator I = CG.begin(), E = CG.end(); I != E; ++I) {
249 CallGraphNode *CGN = I->second;
250 if (CGN == 0 || CGN->getFunction() == 0)
253 Function *F = CGN->getFunction();
255 // If the only remaining users of the function are dead constants, remove
257 F->removeDeadConstantUsers();
259 if (DNR && DNR->count(F))
261 if (!F->hasLinkOnceLinkage() && !F->hasLocalLinkage())
266 // Remove any call graph edges from the function to its callees.
267 CGN->removeAllCalledFunctions();
269 // Remove any edges from the external node to the function's call graph
270 // node. These edges might have been made irrelegant due to
271 // optimization of the program.
272 CG.getExternalCallingNode()->removeAnyCallEdgeTo(CGN);
274 // Removing the node for callee from the call graph and delete it.
275 FunctionsToRemove.insert(CGN);
278 // Now that we know which functions to delete, do so. We didn't want to do
279 // this inline, because that would invalidate our CallGraph::iterator
282 // Note that it doesn't matter that we are iterating over a non-stable set
283 // here to do this, it doesn't matter which order the functions are deleted
285 bool Changed = false;
286 for (SmallPtrSet<CallGraphNode*, 16>::iterator I = FunctionsToRemove.begin(),
287 E = FunctionsToRemove.end(); I != E; ++I) {
288 resetCachedCostInfo((*I)->getFunction());
289 delete CG.removeFunctionFromModule(*I);