| //===- InlineSimple.cpp - Code to perform simple function inlining --------===// |
| // |
| // The LLVM Compiler Infrastructure |
| // |
| // This file was developed by the LLVM research group and is distributed under |
| // the University of Illinois Open Source License. See LICENSE.TXT for details. |
| // |
| //===----------------------------------------------------------------------===// |
| // |
| // This file implements bottom-up inlining of functions into callees. |
| // |
| //===----------------------------------------------------------------------===// |
| |
| #include "Inliner.h" |
| #include "llvm/Function.h" |
| #include "llvm/iMemory.h" |
| #include "llvm/Support/CallSite.h" |
| #include "llvm/Transforms/IPO.h" |
| |
| namespace { |
| // FunctionInfo - For each function, calculate the size of it in blocks and |
| // instructions. |
| struct FunctionInfo { |
| unsigned NumInsts, NumBlocks; |
| |
| FunctionInfo() : NumInsts(0), NumBlocks(0) {} |
| }; |
| |
| class SimpleInliner : public Inliner { |
| std::map<const Function*, FunctionInfo> CachedFunctionInfo; |
| public: |
| int getInlineCost(CallSite CS); |
| }; |
| RegisterOpt<SimpleInliner> X("inline", "Function Integration/Inlining"); |
| } |
| |
| Pass *createFunctionInliningPass() { return new SimpleInliner(); } |
| |
| // getInlineCost - The heuristic used to determine if we should inline the |
| // function call or not. |
| // |
| int SimpleInliner::getInlineCost(CallSite CS) { |
| Instruction *TheCall = CS.getInstruction(); |
| const Function *Callee = CS.getCalledFunction(); |
| const Function *Caller = TheCall->getParent()->getParent(); |
| |
| // Don't inline a directly recursive call. |
| if (Caller == Callee) return 2000000000; |
| |
| // InlineCost - This value measures how good of an inline candidate this call |
| // site is to inline. A lower inline cost make is more likely for the call to |
| // be inlined. This value may go negative. |
| // |
| int InlineCost = 0; |
| |
| // If there is only one call of the function, and it has internal linkage, |
| // make it almost guaranteed to be inlined. |
| // |
| if (Callee->hasInternalLinkage() && Callee->hasOneUse()) |
| InlineCost -= 30000; |
| |
| // Add to the inline quality for properties that make the call valuable to |
| // inline. This includes factors that indicate that the result of inlining |
| // the function will be optimizable. Currently this just looks at arguments |
| // passed into the function. |
| // |
| for (CallSite::arg_iterator I = CS.arg_begin(), E = CS.arg_end(); |
| I != E; ++I) { |
| // Each argument passed in has a cost at both the caller and the callee |
| // sides. This favors functions that take many arguments over functions |
| // that take few arguments. |
| InlineCost -= 20; |
| |
| // If this is a function being passed in, it is very likely that we will be |
| // able to turn an indirect function call into a direct function call. |
| if (isa<Function>(I)) |
| InlineCost -= 100; |
| |
| // If a constant, global variable or alloca is passed in, inlining this |
| // function is likely to allow significant future optimization possibilities |
| // (constant propagation, scalar promotion, and scalarization), so encourage |
| // the inlining of the function. |
| // |
| else if (isa<Constant>(I) || isa<GlobalVariable>(I) || isa<AllocaInst>(I)) |
| InlineCost -= 60; |
| } |
| |
| // Now that we have considered all of the factors that make the call site more |
| // likely to be inlined, look at factors that make us not want to inline it. |
| FunctionInfo &CalleeFI = CachedFunctionInfo[Callee]; |
| |
| // If we haven't calculated this information yet... |
| if (CalleeFI.NumBlocks == 0) { |
| unsigned NumInsts = 0, NumBlocks = 0; |
| |
| // Look at the size of the callee. Each basic block counts as 20 units, and |
| // each instruction counts as 10. |
| for (Function::const_iterator BB = Callee->begin(), E = Callee->end(); |
| BB != E; ++BB) { |
| NumInsts += BB->size(); |
| NumBlocks++; |
| } |
| CalleeFI.NumBlocks = NumBlocks; |
| CalleeFI.NumInsts = NumInsts; |
| } |
| |
| // Don't inline into something too big, which would make it bigger. Here, we |
| // count each basic block as a single unit. |
| InlineCost += Caller->size()*2; |
| |
| |
| // Look at the size of the callee. Each basic block counts as 20 units, and |
| // each instruction counts as 10. |
| InlineCost += CalleeFI.NumInsts*10 + CalleeFI.NumBlocks*20; |
| return InlineCost; |
| } |