1 //===- MethodInlining.cpp - Code to perform method inlining ---------------===//
3 // This file implements inlining of methods.
6 // * Exports functionality to inline any method call
7 // * Inlines methods that consist of a single basic block
8 // * Is able to inline ANY method call
9 // . Has a smart heuristic for when to inline a method
12 // * This pass has a habit of introducing duplicated constant pool entries,
13 // and also opens up a lot of opportunities for constant propogation. It is
14 // a good idea to to run a constant propogation pass, then a DCE pass
15 // sometime after running this pass.
17 // TODO: Currently this throws away all of the symbol names in the method being
18 // inlined to try to avoid name clashes. Use a name if it's not taken
20 //===----------------------------------------------------------------------===//
22 #include "llvm/Optimizations/MethodInlining.h"
23 #include "llvm/Module.h"
24 #include "llvm/Method.h"
25 #include "llvm/iTerminators.h"
26 #include "llvm/iPHINode.h"
27 #include "llvm/iOther.h"
31 #include "llvm/Assembly/Writer.h"
35 // RemapInstruction - Convert the instruction operands from referencing the
36 // current values into those specified by ValueMap.
38 static inline void RemapInstruction(Instruction *I,
39 map<const Value *, Value*> &ValueMap) {
41 for (unsigned op = 0, E = I->getNumOperands(); op != E; ++op) {
42 const Value *Op = I->getOperand(op);
43 Value *V = ValueMap[Op];
44 if (!V && (isa<GlobalValue>(Op) || isa<ConstPoolVal>(Op)))
45 continue; // Globals and constants don't get relocated
48 cerr << "Val = " << endl << Op << "Addr = " << (void*)Op << endl;
49 cerr << "Inst = " << I;
51 assert(V && "Referenced value not in value map!");
56 // InlineMethod - This function forcibly inlines the called method into the
57 // basic block of the caller. This returns false if it is not possible to
58 // inline this call. The program is still in a well defined state if this
61 // Note that this only does one level of inlining. For example, if the
62 // instruction 'call B' is inlined, and 'B' calls 'C', then the call to 'C' now
63 // exists in the instruction stream. Similiarly this will inline a recursive
64 // method by one level.
66 bool opt::InlineMethod(BasicBlock::iterator CIIt) {
67 assert(isa<CallInst>(*CIIt) && "InlineMethod only works on CallInst nodes!");
68 assert((*CIIt)->getParent() && "Instruction not embedded in basic block!");
69 assert((*CIIt)->getParent()->getParent() && "Instruction not in method!");
71 CallInst *CI = cast<CallInst>(*CIIt);
72 const Method *CalledMeth = CI->getCalledMethod();
73 if (CalledMeth == 0 || // Can't inline external method or indirect call!
74 CalledMeth->isExternal()) return false;
75 Method *CurrentMeth = CI->getParent()->getParent();
77 //cerr << "Inlining " << CalledMeth->getName() << " into "
78 // << CurrentMeth->getName() << endl;
80 BasicBlock *OrigBB = CI->getParent();
82 // Call splitBasicBlock - The original basic block now ends at the instruction
83 // immediately before the call. The original basic block now ends with an
84 // unconditional branch to NewBB, and NewBB starts with the call instruction.
86 BasicBlock *NewBB = OrigBB->splitBasicBlock(CIIt);
88 // Remove (unlink) the CallInst from the start of the new basic block.
89 NewBB->getInstList().remove(CI);
91 // If we have a return value generated by this call, convert it into a PHI
92 // node that gets values from each of the old RET instructions in the original
96 if (CalledMeth->getReturnType() != Type::VoidTy) {
97 PHI = new PHINode(CalledMeth->getReturnType(), CI->getName());
99 // The PHI node should go at the front of the new basic block to merge all
100 // possible incoming values.
102 NewBB->getInstList().push_front(PHI);
104 // Anything that used the result of the function call should now use the PHI
105 // node as their operand.
107 CI->replaceAllUsesWith(PHI);
110 // Keep a mapping between the original method's values and the new duplicated
111 // code's values. This includes all of: Method arguments, instruction values,
112 // constant pool entries, and basic blocks.
114 map<const Value *, Value*> ValueMap;
116 // Add the method arguments to the mapping: (start counting at 1 to skip the
117 // method reference itself)
119 Method::ArgumentListType::const_iterator PTI =
120 CalledMeth->getArgumentList().begin();
121 for (unsigned a = 1, E = CI->getNumOperands(); a != E; ++a, ++PTI)
122 ValueMap[*PTI] = CI->getOperand(a);
124 ValueMap[NewBB] = NewBB; // Returns get converted to reference NewBB
126 // Loop over all of the basic blocks in the method, inlining them as
127 // appropriate. Keep track of the first basic block of the method...
129 for (Method::const_iterator BI = CalledMeth->begin();
130 BI != CalledMeth->end(); ++BI) {
131 const BasicBlock *BB = *BI;
132 assert(BB->getTerminator() && "BasicBlock doesn't have terminator!?!?");
134 // Create a new basic block to copy instructions into!
135 BasicBlock *IBB = new BasicBlock("", NewBB->getParent());
137 ValueMap[BB] = IBB; // Add basic block mapping.
139 // Make sure to capture the mapping that a return will use...
140 // TODO: This assumes that the RET is returning a value computed in the same
141 // basic block as the return was issued from!
143 const TerminatorInst *TI = BB->getTerminator();
145 // Loop over all instructions copying them over...
146 Instruction *NewInst;
147 for (BasicBlock::const_iterator II = BB->begin();
148 II != (BB->end()-1); ++II) {
149 IBB->getInstList().push_back((NewInst = (*II)->clone()));
150 ValueMap[*II] = NewInst; // Add instruction map to value.
153 // Copy over the terminator now...
154 switch (TI->getOpcode()) {
155 case Instruction::Ret: {
156 const ReturnInst *RI = cast<const ReturnInst>(TI);
158 if (PHI) { // The PHI node should include this value!
159 assert(RI->getReturnValue() && "Ret should have value!");
160 assert(RI->getReturnValue()->getType() == PHI->getType() &&
161 "Ret value not consistent in method!");
162 PHI->addIncoming((Value*)RI->getReturnValue(), cast<BasicBlock>(BB));
165 // Add a branch to the code that was after the original Call.
166 IBB->getInstList().push_back(new BranchInst(NewBB));
169 case Instruction::Br:
170 IBB->getInstList().push_back(TI->clone());
174 cerr << "MethodInlining: Don't know how to handle terminator: " << TI;
180 // Loop over all of the instructions in the method, fixing up operand
181 // references as we go. This uses ValueMap to do all the hard work.
183 for (Method::const_iterator BI = CalledMeth->begin();
184 BI != CalledMeth->end(); ++BI) {
185 const BasicBlock *BB = *BI;
186 BasicBlock *NBB = (BasicBlock*)ValueMap[BB];
188 // Loop over all instructions, fixing each one as we find it...
190 for (BasicBlock::iterator II = NBB->begin(); II != NBB->end(); II++)
191 RemapInstruction(*II, ValueMap);
194 if (PHI) RemapInstruction(PHI, ValueMap); // Fix the PHI node also...
196 // Change the branch that used to go to NewBB to branch to the first basic
197 // block of the inlined method.
199 TerminatorInst *Br = OrigBB->getTerminator();
200 assert(Br && Br->getOpcode() == Instruction::Br &&
201 "splitBasicBlock broken!");
202 Br->setOperand(0, ValueMap[CalledMeth->front()]);
204 // Since we are now done with the CallInst, we can finally delete it.
209 bool opt::InlineMethod(CallInst *CI) {
210 assert(CI->getParent() && "CallInst not embeded in BasicBlock!");
211 BasicBlock *PBB = CI->getParent();
213 BasicBlock::iterator CallIt = find(PBB->begin(), PBB->end(), CI);
215 assert(CallIt != PBB->end() &&
216 "CallInst has parent that doesn't contain CallInst?!?");
217 return InlineMethod(CallIt);
220 static inline bool ShouldInlineMethod(const CallInst *CI, const Method *M) {
221 assert(CI->getParent() && CI->getParent()->getParent() &&
222 "Call not embedded into a method!");
224 // Don't inline a recursive call.
225 if (CI->getParent()->getParent() == M) return false;
227 // Don't inline something too big. This is a really crappy heuristic
228 if (M->size() > 3) return false;
230 // Don't inline into something too big. This is a **really** crappy heuristic
231 if (CI->getParent()->getParent()->size() > 10) return false;
233 // Go ahead and try just about anything else.
238 static inline bool DoMethodInlining(BasicBlock *BB) {
239 for (BasicBlock::iterator I = BB->begin(); I != BB->end(); ++I) {
240 if (CallInst *CI = dyn_cast<CallInst>(*I)) {
241 // Check to see if we should inline this method
242 Method *M = CI->getCalledMethod();
243 if (M && ShouldInlineMethod(CI, M))
244 return InlineMethod(I);
250 bool opt::MethodInlining::doMethodInlining(Method *M) {
251 bool Changed = false;
253 // Loop through now and inline instructions a basic block at a time...
254 for (Method::iterator I = M->begin(); I != M->end(); )
255 if (DoMethodInlining(*I)) {
257 // Iterator is now invalidated by new basic blocks inserted