1 //===- Inliner.cpp - Code common to all inliners --------------------------===//
3 // The LLVM Compiler Infrastructure
5 // This file was developed by the LLVM research group and is distributed under
6 // the University of Illinois Open Source 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"
18 #include "llvm/Module.h"
19 #include "llvm/Instructions.h"
20 #include "llvm/Analysis/CallGraph.h"
21 #include "llvm/Support/CallSite.h"
22 #include "llvm/Transforms/Utils/Cloning.h"
23 #include "llvm/Support/CommandLine.h"
24 #include "llvm/Support/Debug.h"
25 #include "llvm/ADT/Statistic.h"
29 STATISTIC(NumInlined, "Number of functions inlined");
30 STATISTIC(NumDeleted, "Number of functions deleted because all callers found");
33 cl::opt<unsigned> // FIXME: 200 is VERY conservative
34 InlineLimit("inline-threshold", cl::Hidden, cl::init(200),
35 cl::desc("Control the amount of inlining to perform (default = 200)"));
38 Inliner::Inliner() : InlineThreshold(InlineLimit) {}
40 // InlineCallIfPossible - If it is possible to inline the specified call site,
41 // do so and update the CallGraph for this operation.
42 static bool InlineCallIfPossible(CallSite CS, CallGraph &CG,
43 const std::set<Function*> &SCCFunctions) {
44 Function *Callee = CS.getCalledFunction();
45 if (!InlineFunction(CS, &CG)) return false;
47 // If we inlined the last possible call site to the function, delete the
49 if (Callee->use_empty() && Callee->hasInternalLinkage() &&
50 !SCCFunctions.count(Callee)) {
51 DOUT << " -> Deleting dead function: " << Callee->getName() << "\n";
53 // Remove any call graph edges from the callee to its callees.
54 CallGraphNode *CalleeNode = CG[Callee];
55 while (CalleeNode->begin() != CalleeNode->end())
56 CalleeNode->removeCallEdgeTo((CalleeNode->end()-1)->second);
58 // Removing the node for callee from the call graph and delete it.
59 delete CG.removeFunctionFromModule(CalleeNode);
65 bool Inliner::runOnSCC(const std::vector<CallGraphNode*> &SCC) {
66 CallGraph &CG = getAnalysis<CallGraph>();
68 std::set<Function*> SCCFunctions;
69 DOUT << "Inliner visiting SCC:";
70 for (unsigned i = 0, e = SCC.size(); i != e; ++i) {
71 Function *F = SCC[i]->getFunction();
72 if (F) SCCFunctions.insert(F);
73 DOUT << " " << (F ? F->getName() : "INDIRECTNODE");
76 // Scan through and identify all call sites ahead of time so that we only
77 // inline call sites in the original functions, not call sites that result
78 // from inlining other functions.
79 std::vector<CallSite> CallSites;
81 for (unsigned i = 0, e = SCC.size(); i != e; ++i)
82 if (Function *F = SCC[i]->getFunction())
83 for (Function::iterator BB = F->begin(), E = F->end(); BB != E; ++BB)
84 for (BasicBlock::iterator I = BB->begin(); I != BB->end(); ++I) {
85 CallSite CS = CallSite::get(I);
86 if (CS.getInstruction() && (!CS.getCalledFunction() ||
87 !CS.getCalledFunction()->isExternal()))
88 CallSites.push_back(CS);
91 DOUT << ": " << CallSites.size() << " call sites.\n";
93 // Now that we have all of the call sites, move the ones to functions in the
94 // current SCC to the end of the list.
95 unsigned FirstCallInSCC = CallSites.size();
96 for (unsigned i = 0; i < FirstCallInSCC; ++i)
97 if (Function *F = CallSites[i].getCalledFunction())
98 if (SCCFunctions.count(F))
99 std::swap(CallSites[i--], CallSites[--FirstCallInSCC]);
101 // Now that we have all of the call sites, loop over them and inline them if
102 // it looks profitable to do so.
103 bool Changed = false;
107 // Iterate over the outer loop because inlining functions can cause indirect
108 // calls to become direct calls.
109 for (unsigned CSi = 0; CSi != CallSites.size(); ++CSi)
110 if (Function *Callee = CallSites[CSi].getCalledFunction()) {
111 // Calls to external functions are never inlinable.
112 if (Callee->isExternal() ||
113 CallSites[CSi].getInstruction()->getParent()->getParent() ==Callee){
114 if (SCC.size() == 1) {
115 std::swap(CallSites[CSi], CallSites.back());
116 CallSites.pop_back();
118 // Keep the 'in SCC / not in SCC' boundary correct.
119 CallSites.erase(CallSites.begin()+CSi);
125 // If the policy determines that we should inline this function,
127 CallSite CS = CallSites[CSi];
128 int InlineCost = getInlineCost(CS);
129 if (InlineCost >= (int)InlineThreshold) {
130 DOUT << " NOT Inlining: cost=" << InlineCost
131 << ", Call: " << *CS.getInstruction();
133 DOUT << " Inlining: cost=" << InlineCost
134 << ", Call: " << *CS.getInstruction();
136 // Attempt to inline the function...
137 if (InlineCallIfPossible(CS, CG, SCCFunctions)) {
138 // Remove this call site from the list. If possible, use
139 // swap/pop_back for efficiency, but do not use it if doing so would
140 // move a call site to a function in this SCC before the
141 // 'FirstCallInSCC' barrier.
142 if (SCC.size() == 1) {
143 std::swap(CallSites[CSi], CallSites.back());
144 CallSites.pop_back();
146 CallSites.erase(CallSites.begin()+CSi);
156 } while (LocalChange);
161 // doFinalization - Remove now-dead linkonce functions at the end of
162 // processing to avoid breaking the SCC traversal.
163 bool Inliner::doFinalization(CallGraph &CG) {
164 std::set<CallGraphNode*> FunctionsToRemove;
166 // Scan for all of the functions, looking for ones that should now be removed
167 // from the program. Insert the dead ones in the FunctionsToRemove set.
168 for (CallGraph::iterator I = CG.begin(), E = CG.end(); I != E; ++I) {
169 CallGraphNode *CGN = I->second;
170 if (Function *F = CGN ? CGN->getFunction() : 0) {
171 // If the only remaining users of the function are dead constants, remove
173 F->removeDeadConstantUsers();
175 if ((F->hasLinkOnceLinkage() || F->hasInternalLinkage()) &&
178 // Remove any call graph edges from the function to its callees.
179 while (CGN->begin() != CGN->end())
180 CGN->removeCallEdgeTo((CGN->end()-1)->second);
182 // Remove any edges from the external node to the function's call graph
183 // node. These edges might have been made irrelegant due to
184 // optimization of the program.
185 CG.getExternalCallingNode()->removeAnyCallEdgeTo(CGN);
187 // Removing the node for callee from the call graph and delete it.
188 FunctionsToRemove.insert(CGN);
193 // Now that we know which functions to delete, do so. We didn't want to do
194 // this inline, because that would invalidate our CallGraph::iterator
196 bool Changed = false;
197 for (std::set<CallGraphNode*>::iterator I = FunctionsToRemove.begin(),
198 E = FunctionsToRemove.end(); I != E; ++I) {
199 delete CG.removeFunctionFromModule(*I);