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/InlineCost.h"
25 #include "llvm/Transforms/Utils/Cloning.h"
26 #include "llvm/Support/CommandLine.h"
27 #include "llvm/Support/Debug.h"
28 #include "llvm/Support/raw_ostream.h"
29 #include "llvm/ADT/SmallPtrSet.h"
30 #include "llvm/ADT/Statistic.h"
34 STATISTIC(NumInlined, "Number of functions inlined");
35 STATISTIC(NumDeleted, "Number of functions deleted because all callers found");
38 InlineLimit("inline-threshold", cl::Hidden, cl::init(200), cl::ZeroOrMore,
39 cl::desc("Control the amount of inlining to perform (default = 200)"));
41 Inliner::Inliner(void *ID)
42 : CallGraphSCCPass(ID), InlineThreshold(InlineLimit) {}
44 Inliner::Inliner(void *ID, int Threshold)
45 : CallGraphSCCPass(ID), InlineThreshold(Threshold) {}
47 /// getAnalysisUsage - For this class, we declare that we require and preserve
48 /// the call graph. If the derived class implements this method, it should
49 /// always explicitly call the implementation here.
50 void Inliner::getAnalysisUsage(AnalysisUsage &Info) const {
51 CallGraphSCCPass::getAnalysisUsage(Info);
54 // InlineCallIfPossible - If it is possible to inline the specified call site,
55 // do so and update the CallGraph for this operation.
56 bool Inliner::InlineCallIfPossible(CallSite CS, CallGraph &CG,
57 const SmallPtrSet<Function*, 8> &SCCFunctions,
58 const TargetData *TD) {
59 Function *Callee = CS.getCalledFunction();
60 Function *Caller = CS.getCaller();
62 if (!InlineFunction(CS, &CG, TD))
65 // If the inlined function had a higher stack protection level than the
66 // calling function, then bump up the caller's stack protection level.
67 if (Callee->hasFnAttr(Attribute::StackProtectReq))
68 Caller->addFnAttr(Attribute::StackProtectReq);
69 else if (Callee->hasFnAttr(Attribute::StackProtect) &&
70 !Caller->hasFnAttr(Attribute::StackProtectReq))
71 Caller->addFnAttr(Attribute::StackProtect);
73 // If we inlined the last possible call site to the function, delete the
75 if (Callee->use_empty() &&
76 (Callee->hasLocalLinkage() || Callee->hasAvailableExternallyLinkage()) &&
77 !SCCFunctions.count(Callee)) {
78 DEBUG(errs() << " -> Deleting dead function: "
79 << Callee->getName() << "\n");
80 CallGraphNode *CalleeNode = CG[Callee];
82 // Remove any call graph edges from the callee to its callees.
83 CalleeNode->removeAllCalledFunctions();
85 resetCachedCostInfo(CalleeNode->getFunction());
87 // Removing the node for callee from the call graph and delete it.
88 delete CG.removeFunctionFromModule(CalleeNode);
94 /// shouldInline - Return true if the inliner should attempt to inline
95 /// at the given CallSite.
96 bool Inliner::shouldInline(CallSite CS) {
97 InlineCost IC = getInlineCost(CS);
100 DEBUG(errs() << " Inlining: cost=always"
101 << ", Call: " << *CS.getInstruction() << "\n");
106 DEBUG(errs() << " NOT Inlining: cost=never"
107 << ", Call: " << *CS.getInstruction() << "\n");
111 int Cost = IC.getValue();
112 int CurrentThreshold = InlineThreshold;
113 Function *Fn = CS.getCaller();
114 if (Fn && !Fn->isDeclaration() &&
115 Fn->hasFnAttr(Attribute::OptimizeForSize) &&
116 InlineThreshold != 50)
117 CurrentThreshold = 50;
119 float FudgeFactor = getInlineFudgeFactor(CS);
120 if (Cost >= (int)(CurrentThreshold * FudgeFactor)) {
121 DEBUG(errs() << " NOT Inlining: cost=" << Cost
122 << ", Call: " << *CS.getInstruction() << "\n");
126 DEBUG(errs() << " Inlining: cost=" << Cost
127 << ", Call: " << *CS.getInstruction() << "\n");
131 bool Inliner::runOnSCC(const std::vector<CallGraphNode*> &SCC) {
132 CallGraph &CG = getAnalysis<CallGraph>();
133 const TargetData *TD = getAnalysisIfAvailable<TargetData>();
135 SmallPtrSet<Function*, 8> SCCFunctions;
136 DEBUG(errs() << "Inliner visiting SCC:");
137 for (unsigned i = 0, e = SCC.size(); i != e; ++i) {
138 Function *F = SCC[i]->getFunction();
139 if (F) SCCFunctions.insert(F);
140 DEBUG(errs() << " " << (F ? F->getName() : "INDIRECTNODE"));
143 // Scan through and identify all call sites ahead of time so that we only
144 // inline call sites in the original functions, not call sites that result
145 // from inlining other functions.
146 std::vector<CallSite> CallSites;
148 for (unsigned i = 0, e = SCC.size(); i != e; ++i) {
149 Function *F = SCC[i]->getFunction();
152 for (Function::iterator BB = F->begin(), E = F->end(); BB != E; ++BB)
153 for (BasicBlock::iterator I = BB->begin(), E = BB->end(); I != E; ++I) {
154 CallSite CS = CallSite::get(I);
155 if (CS.getInstruction() == 0 || isa<DbgInfoIntrinsic>(I))
158 if (CS.getCalledFunction() == 0 ||
159 !CS.getCalledFunction()->isDeclaration())
160 CallSites.push_back(CS);
164 DEBUG(errs() << ": " << CallSites.size() << " call sites.\n");
166 // Now that we have all of the call sites, move the ones to functions in the
167 // current SCC to the end of the list.
168 unsigned FirstCallInSCC = CallSites.size();
169 for (unsigned i = 0; i < FirstCallInSCC; ++i)
170 if (Function *F = CallSites[i].getCalledFunction())
171 if (SCCFunctions.count(F))
172 std::swap(CallSites[i--], CallSites[--FirstCallInSCC]);
174 // Now that we have all of the call sites, loop over them and inline them if
175 // it looks profitable to do so.
176 bool Changed = false;
180 // Iterate over the outer loop because inlining functions can cause indirect
181 // calls to become direct calls.
182 for (unsigned CSi = 0; CSi != CallSites.size(); ++CSi) {
183 // We can only inline direct calls.
184 Function *Callee = CallSites[CSi].getCalledFunction();
185 if (!Callee) continue;
187 // Calls to external functions are never inlinable.
188 if (Callee->isDeclaration()) {
189 if (SCC.size() == 1) {
190 std::swap(CallSites[CSi], CallSites.back());
191 CallSites.pop_back();
193 // Keep the 'in SCC / not in SCC' boundary correct.
194 CallSites.erase(CallSites.begin()+CSi);
200 // If the policy determines that we should inline this function,
202 CallSite CS = CallSites[CSi];
203 if (!shouldInline(CS))
206 Function *Caller = CS.getCaller();
207 // Attempt to inline the function...
208 if (!InlineCallIfPossible(CS, CG, SCCFunctions, TD))
211 // Remove any cached cost info for this caller, as inlining the
212 // callee has increased the size of the caller (which may be the
213 // same as the callee).
214 resetCachedCostInfo(Caller);
216 // Remove this call site from the list. If possible, use
217 // swap/pop_back for efficiency, but do not use it if doing so would
218 // move a call site to a function in this SCC before the
219 // 'FirstCallInSCC' barrier.
220 if (SCC.size() == 1) {
221 std::swap(CallSites[CSi], CallSites.back());
222 CallSites.pop_back();
224 CallSites.erase(CallSites.begin()+CSi);
232 } while (LocalChange);
237 // doFinalization - Remove now-dead linkonce functions at the end of
238 // processing to avoid breaking the SCC traversal.
239 bool Inliner::doFinalization(CallGraph &CG) {
240 return removeDeadFunctions(CG);
243 /// removeDeadFunctions - Remove dead functions that are not included in
244 /// DNR (Do Not Remove) list.
245 bool Inliner::removeDeadFunctions(CallGraph &CG,
246 SmallPtrSet<const Function *, 16> *DNR) {
247 SmallPtrSet<CallGraphNode*, 16> FunctionsToRemove;
249 // Scan for all of the functions, looking for ones that should now be removed
250 // from the program. Insert the dead ones in the FunctionsToRemove set.
251 for (CallGraph::iterator I = CG.begin(), E = CG.end(); I != E; ++I) {
252 CallGraphNode *CGN = I->second;
253 if (CGN == 0 || CGN->getFunction() == 0)
256 Function *F = CGN->getFunction();
258 // If the only remaining users of the function are dead constants, remove
260 F->removeDeadConstantUsers();
262 if (DNR && DNR->count(F))
264 if (!F->hasLinkOnceLinkage() && !F->hasLocalLinkage())
269 // Remove any call graph edges from the function to its callees.
270 CGN->removeAllCalledFunctions();
272 // Remove any edges from the external node to the function's call graph
273 // node. These edges might have been made irrelegant due to
274 // optimization of the program.
275 CG.getExternalCallingNode()->removeAnyCallEdgeTo(CGN);
277 // Removing the node for callee from the call graph and delete it.
278 FunctionsToRemove.insert(CGN);
281 // Now that we know which functions to delete, do so. We didn't want to do
282 // this inline, because that would invalidate our CallGraph::iterator
285 // Note that it doesn't matter that we are iterating over a non-stable set
286 // here to do this, it doesn't matter which order the functions are deleted
288 bool Changed = false;
289 for (SmallPtrSet<CallGraphNode*, 16>::iterator I = FunctionsToRemove.begin(),
290 E = FunctionsToRemove.end(); I != E; ++I) {
291 resetCachedCostInfo((*I)->getFunction());
292 delete CG.removeFunctionFromModule(*I);