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Add BasicInliner interface.

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This interface allows clients to inline bunch of functions with module
level call graph information.:wq

llvm-svn: 40486
This commit is contained in:
Devang Patel 2007-07-25 18:00:25 +00:00
parent 95a78a7963
commit d7b401bafd
5 changed files with 553 additions and 246 deletions
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55
include/llvm/Transforms/Utils/BasicInliner.h Normal file
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@ -0,0 +1,55 @@
//===- BasicInliner.h - Basic function level inliner ------------*- C++ -*-===//
//
// The LLVM Compiler Infrastructure
//
// This file was developed by Devang Patel and is distributed under
// the University of Illinois Open Source License. See LICENSE.TXT for details.
//
//===----------------------------------------------------------------------===//
//
// This file defines a simple function based inliner that does not use
// call graph information.
//
//===----------------------------------------------------------------------===//
#ifndef BASICINLINER_H
#define BASICINLINER_H
#include "llvm/Transforms/Utils/InlineCost.h"
namespace llvm {
class Function;
class TargetData;
class BasicInlinerImpl;
/// BasicInliner - BasicInliner provides function level inlining interface.
/// Clients provide list of functions which are inline without using
/// module level call graph information. Note that the BasicInliner is
/// free to delete a function if it is inlined into all call sites.
class BasicInliner {
public:
BasicInliner(TargetData *T = NULL);
~BasicInliner();
/// addFunction - Add function into the list of functions to process.
/// All functions must be inserted using this interface before invoking
/// inlineFunctions().
void addFunction(Function *F);
/// neverInlineFunction - Sometimes a function is never to be inlined
/// because of one or other reason.
void neverInlineFunction(Function *F);
/// inlineFuctions - Walk all call sites in all functions supplied by
/// client. Inline as many call sites as possible. Delete completely
/// inlined functions.
void inlineFunctions();
private:
BasicInlinerImpl *Impl;
};
}
#endif

80
include/llvm/Transforms/Utils/InlineCost.h Normal file
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@ -0,0 +1,80 @@
//===- InlineCost.cpp - Cost analysis for inliner ---------------*- C++ -*-===//
//
// 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.
//
//===----------------------------------------------------------------------===//
#ifndef INLINECOST_H
#define INLINECOST_H
#include <set>
#include <map>
#include <vector>
namespace llvm {
class Value;
class Function;
class CallSite;
/// InlineCostAnalyzer - Cost analyzer used by inliner.
class InlineCostAnalyzer {
struct ArgInfo {
public:
unsigned ConstantWeight;
unsigned AllocaWeight;
ArgInfo(unsigned CWeight, unsigned AWeight)
: ConstantWeight(CWeight), AllocaWeight(AWeight) {}
};
// FunctionInfo - For each function, calculate the size of it in blocks and
// instructions.
struct FunctionInfo {
// NumInsts, NumBlocks - Keep track of how large each function is, which is
// used to estimate the code size cost of inlining it.
unsigned NumInsts, NumBlocks;
// ArgumentWeights - Each formal argument of the function is inspected to
// see if it is used in any contexts where making it a constant or alloca
// would reduce the code size. If so, we add some value to the argument
// entry here.
std::vector<ArgInfo> ArgumentWeights;
FunctionInfo() : NumInsts(0), NumBlocks(0) {}
/// analyzeFunction - Fill in the current structure with information gleaned
/// from the specified function.
void analyzeFunction(Function *F);
// CountCodeReductionForConstant - Figure out an approximation for how many
// instructions will be constant folded if the specified value is constant.
//
unsigned CountCodeReductionForConstant(Value *V);
// CountCodeReductionForAlloca - Figure out an approximation of how much smaller
// the function will be if it is inlined into a context where an argument
// becomes an alloca.
//
unsigned CountCodeReductionForAlloca(Value *V);
};
std::map<const Function *, FunctionInfo>CachedFunctionInfo;
public:
// getInlineCost - The heuristic used to determine if we should inline the
// function call or not.
//
int getInlineCost(CallSite CS, std::set<const Function *> &NeverInline);
};
}
#endif

252
lib/Transforms/IPO/InlineSimple.cpp
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@ -22,46 +22,22 @@
#include "llvm/Support/Compiler.h"
#include "llvm/Transforms/IPO.h"
#include "llvm/Transforms/IPO/InlinerPass.h"
#include "llvm/Transforms/Utils/InlineCost.h"
#include <set>
using namespace llvm;
namespace {
struct VISIBILITY_HIDDEN ArgInfo {
unsigned ConstantWeight;
unsigned AllocaWeight;
ArgInfo(unsigned CWeight, unsigned AWeight)
: ConstantWeight(CWeight), AllocaWeight(AWeight) {}
};
// FunctionInfo - For each function, calculate the size of it in blocks and
// instructions.
struct VISIBILITY_HIDDEN FunctionInfo {
// NumInsts, NumBlocks - Keep track of how large each function is, which is
// used to estimate the code size cost of inlining it.
unsigned NumInsts, NumBlocks;
// ArgumentWeights - Each formal argument of the function is inspected to
// see if it is used in any contexts where making it a constant or alloca
// would reduce the code size. If so, we add some value to the argument
// entry here.
std::vector<ArgInfo> ArgumentWeights;
FunctionInfo() : NumInsts(0), NumBlocks(0) {}
/// analyzeFunction - Fill in the current structure with information gleaned
/// from the specified function.
void analyzeFunction(Function *F);
};
class VISIBILITY_HIDDEN SimpleInliner : public Inliner {
std::map<const Function*, FunctionInfo> CachedFunctionInfo;
std::set<const Function*> NeverInline; // Functions that are never inlined
InlineCostAnalyzer CA;
public:
SimpleInliner() : Inliner(&ID) {}
static char ID; // Pass identification, replacement for typeid
int getInlineCost(CallSite CS);
int getInlineCost(CallSite CS) {
return CA.getInlineCost(CS, NeverInline);
}
virtual bool doInitialization(CallGraph &CG);
};
char SimpleInliner::ID = 0;
@ -70,223 +46,6 @@ namespace {
Pass *llvm::createFunctionInliningPass() { return new SimpleInliner(); }
// CountCodeReductionForConstant - Figure out an approximation for how many
// instructions will be constant folded if the specified value is constant.
//
static unsigned CountCodeReductionForConstant(Value *V) {
unsigned Reduction = 0;
for (Value::use_iterator UI = V->use_begin(), E = V->use_end(); UI != E; ++UI)
if (isa<BranchInst>(*UI))
Reduction += 40; // Eliminating a conditional branch is a big win
else if (SwitchInst *SI = dyn_cast<SwitchInst>(*UI))
// Eliminating a switch is a big win, proportional to the number of edges
// deleted.
Reduction += (SI->getNumSuccessors()-1) * 40;
else if (CallInst *CI = dyn_cast<CallInst>(*UI)) {
// Turning an indirect call into a direct call is a BIG win
Reduction += CI->getCalledValue() == V ? 500 : 0;
} else if (InvokeInst *II = dyn_cast<InvokeInst>(*UI)) {
// Turning an indirect call into a direct call is a BIG win
Reduction += II->getCalledValue() == V ? 500 : 0;
} else {
// Figure out if this instruction will be removed due to simple constant
// propagation.
Instruction &Inst = cast<Instruction>(**UI);
bool AllOperandsConstant = true;
for (unsigned i = 0, e = Inst.getNumOperands(); i != e; ++i)
if (!isa<Constant>(Inst.getOperand(i)) && Inst.getOperand(i) != V) {
AllOperandsConstant = false;
break;
}
if (AllOperandsConstant) {
// We will get to remove this instruction...
Reduction += 7;
// And any other instructions that use it which become constants
// themselves.
Reduction += CountCodeReductionForConstant(&Inst);
}
}
return Reduction;
}
// CountCodeReductionForAlloca - Figure out an approximation of how much smaller
// the function will be if it is inlined into a context where an argument
// becomes an alloca.
//
static unsigned CountCodeReductionForAlloca(Value *V) {
if (!isa<PointerType>(V->getType())) return 0; // Not a pointer
unsigned Reduction = 0;
for (Value::use_iterator UI = V->use_begin(), E = V->use_end(); UI != E;++UI){
Instruction *I = cast<Instruction>(*UI);
if (isa<LoadInst>(I) || isa<StoreInst>(I))
Reduction += 10;
else if (GetElementPtrInst *GEP = dyn_cast<GetElementPtrInst>(I)) {
// If the GEP has variable indices, we won't be able to do much with it.
for (Instruction::op_iterator I = GEP->op_begin()+1, E = GEP->op_end();
I != E; ++I)
if (!isa<Constant>(*I)) return 0;
Reduction += CountCodeReductionForAlloca(GEP)+15;
} else {
// If there is some other strange instruction, we're not going to be able
// to do much if we inline this.
return 0;
}
}
return Reduction;
}
/// analyzeFunction - Fill in the current structure with information gleaned
/// from the specified function.
void FunctionInfo::analyzeFunction(Function *F) {
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 = F->begin(), E = F->end(); BB != E; ++BB) {
for (BasicBlock::const_iterator II = BB->begin(), E = BB->end();
II != E; ++II) {
if (isa<DbgInfoIntrinsic>(II)) continue; // Debug intrinsics don't count.
// Noop casts, including ptr <-> int, don't count.
if (const CastInst *CI = dyn_cast<CastInst>(II)) {
if (CI->isLosslessCast() || isa<IntToPtrInst>(CI) ||
isa<PtrToIntInst>(CI))
continue;
} else if (const GetElementPtrInst *GEPI =
dyn_cast<GetElementPtrInst>(II)) {
// If a GEP has all constant indices, it will probably be folded with
// a load/store.
bool AllConstant = true;
for (unsigned i = 1, e = GEPI->getNumOperands(); i != e; ++i)
if (!isa<ConstantInt>(GEPI->getOperand(i))) {
AllConstant = false;
break;
}
if (AllConstant) continue;
}
++NumInsts;
}
++NumBlocks;
}
this->NumBlocks = NumBlocks;
this->NumInsts = NumInsts;
// Check out all of the arguments to the function, figuring out how much
// code can be eliminated if one of the arguments is a constant.
for (Function::arg_iterator I = F->arg_begin(), E = F->arg_end(); I != E; ++I)
ArgumentWeights.push_back(ArgInfo(CountCodeReductionForConstant(I),
CountCodeReductionForAlloca(I)));
}
// getInlineCost - The heuristic used to determine if we should inline the
// function call or not.
//
int SimpleInliner::getInlineCost(CallSite CS) {
Instruction *TheCall = CS.getInstruction();
Function *Callee = CS.getCalledFunction();
const Function *Caller = TheCall->getParent()->getParent();
// Don't inline a directly recursive call.
if (Caller == Callee ||
// Don't inline functions which can be redefined at link-time to mean
// something else. link-once linkage is ok though.
Callee->hasWeakLinkage() ||
// Don't inline functions marked noinline.
NeverInline.count(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;
// If this function uses the coldcc calling convention, prefer not to inline
// it.
if (Callee->getCallingConv() == CallingConv::Cold)
InlineCost += 2000;
// If the instruction after the call, or if the normal destination of the
// invoke is an unreachable instruction, the function is noreturn. As such,
// there is little point in inlining this.
if (InvokeInst *II = dyn_cast<InvokeInst>(TheCall)) {
if (isa<UnreachableInst>(II->getNormalDest()->begin()))
InlineCost += 10000;
} else if (isa<UnreachableInst>(++BasicBlock::iterator(TheCall)))
InlineCost += 10000;
// Get information about the callee...
FunctionInfo &CalleeFI = CachedFunctionInfo[Callee];
// If we haven't calculated this information yet, do so now.
if (CalleeFI.NumBlocks == 0)
CalleeFI.analyzeFunction(Callee);
// 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.
//
unsigned ArgNo = 0;
for (CallSite::arg_iterator I = CS.arg_begin(), E = CS.arg_end();
I != E; ++I, ++ArgNo) {
// 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 an alloca is passed in, inlining this function is likely to allow
// significant future optimization possibilities (like scalar promotion, and
// scalarization), so encourage the inlining of the function.
//
else if (isa<AllocaInst>(I)) {
if (ArgNo < CalleeFI.ArgumentWeights.size())
InlineCost -= CalleeFI.ArgumentWeights[ArgNo].AllocaWeight;
// If this is a constant being passed into the function, use the argument
// weights calculated for the callee to determine how much will be folded
// away with this information.
} else if (isa<Constant>(I)) {
if (ArgNo < CalleeFI.ArgumentWeights.size())
InlineCost -= CalleeFI.ArgumentWeights[ArgNo].ConstantWeight;
}
}
// 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.
// 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()/20;
// Look at the size of the callee. Each basic block counts as 20 units, and
// each instruction counts as 5.
InlineCost += CalleeFI.NumInsts*5 + CalleeFI.NumBlocks*20;
return InlineCost;
}
// doInitialization - Initializes the vector of functions that have been
// annotated with the noinline attribute.
bool SimpleInliner::doInitialization(CallGraph &CG) {
@ -321,3 +80,4 @@ bool SimpleInliner::doInitialization(CallGraph &CG) {
return false;
}

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lib/Transforms/Utils/BasicInliner.cpp Normal file
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//===- BasicInliner.cpp - Basic function level inliner --------------------===//
//
// The LLVM Compiler Infrastructure
//
// This file was developed by Devang Patel and is distributed under
// the University of Illinois Open Source License. See LICENSE.TXT for details.
//
//===----------------------------------------------------------------------===//
//
// This file defines a simple function based inliner that does not use
// call graph information.
//
//===----------------------------------------------------------------------===//
#define DEBUG_TYPE "basicinliner"
#include "llvm/Module.h"
#include "llvm/Function.h"
#include "llvm/Transforms/Utils/BasicInliner.h"
#include "llvm/Transforms/Utils/Cloning.h"
#include "llvm/Support/CallSite.h"
#include "llvm/Support/CommandLine.h"
#include "llvm/Support/Debug.h"
#include "llvm/ADT/SmallPtrSet.h"
#include <vector>
#include <set>
using namespace llvm;
namespace {
cl::opt<unsigned>
BasicInlineThreshold("inline-threshold", cl::Hidden, cl::init(200),
cl::desc("Control the amount of basic inlining to perform (default = 200)"));
}
namespace llvm {
/// BasicInlinerImpl - BasicInliner implemantation class. This hides
/// container info, used by basic inliner, from public interface.
struct VISIBILITY_HIDDEN BasicInlinerImpl {
BasicInlinerImpl(const BasicInlinerImpl&); // DO NOT IMPLEMENT
void operator=(const BasicInlinerImpl&); // DO NO IMPLEMENT
public:
BasicInlinerImpl(TargetData *T) : TD(T) {}
/// addFunction - Add function into the list of functions to process.
/// All functions must be inserted using this interface before invoking
/// inlineFunctions().
void addFunction(Function *F) {
Functions.push_back(F);
}
/// neverInlineFunction - Sometimes a function is never to be inlined
/// because of one or other reason.
void neverInlineFunction(Function *F) {
NeverInline.insert(F);
}
/// inlineFuctions - Walk all call sites in all functions supplied by
/// client. Inline as many call sites as possible. Delete completely
/// inlined functions.
void inlineFunctions();
private:
TargetData *TD;
std::vector<Function *> Functions;
std::set<const Function *> NeverInline;
SmallPtrSet<Function *, 8> DeadFunctions;
InlineCostAnalyzer CA;
};
/// inlineFuctions - Walk all call sites in all functions supplied by
/// client. Inline as many call sites as possible. Delete completely
/// inlined functions.
void BasicInlinerImpl::inlineFunctions() {
// Scan through and identify all call sites ahead of time so that we only
// inline call sites in the original functions, not call sites that result
// from inlining other functions.
std::vector<CallSite> CallSites;
for (std::vector<Function *>::iterator FI = Functions.begin(),
FE = Functions.end(); FI != FE; ++FI) {
Function *F = *FI;
for (Function::iterator BB = F->begin(), E = F->end(); BB != E; ++BB)
for (BasicBlock::iterator I = BB->begin(); I != BB->end(); ++I) {
CallSite CS = CallSite::get(I);
if (CS.getInstruction() && CS.getCalledFunction()
&& !CS.getCalledFunction()->isDeclaration())
CallSites.push_back(CS);
}
}
DOUT << ": " << CallSites.size() << " call sites.\n";
// Inline call sites.
bool Changed = false;
do {
Changed = false;
for (unsigned index = 0; index != CallSites.size() && !CallSites.empty(); ++index) {
CallSite CS = CallSites[index];
if (Function *Callee = CS.getCalledFunction()) {
// Eliminate calls taht are never inlinable.
if (Callee->isDeclaration() ||
CS.getInstruction()->getParent()->getParent() == Callee) {
CallSites.erase(CallSites.begin() + index);
--index;
continue;
}
int InlineCost = CA.getInlineCost(CS, NeverInline);
if (InlineCost >= (int) BasicInlineThreshold) {
DOUT << " NOT Inlining: cost = " << InlineCost
<< ", call: " << *CS.getInstruction();
continue;
}
DOUT << " Inlining: cost=" << InlineCost
<<", call: " << *CS.getInstruction();
// Inline
if (InlineFunction(CS, NULL, TD)) {
if (Callee->use_empty() && Callee->hasInternalLinkage())
DeadFunctions.insert(Callee);
Changed = true;
CallSites.erase(CallSites.begin() + index);
--index;
}
}
}
} while (Changed);
// Remove completely inlined functions from module.
for(SmallPtrSet<Function *, 8>::iterator I = DeadFunctions.begin(),
E = DeadFunctions.end(); I != E; ++I) {
Function *D = *I;
Module *M = D->getParent();
M->getFunctionList().remove(D);
}
}
BasicInliner::BasicInliner(TargetData *TD) {
Impl = new BasicInlinerImpl(TD);
}
BasicInliner::~BasicInliner() {
delete Impl;
}
/// addFunction - Add function into the list of functions to process.
/// All functions must be inserted using this interface before invoking
/// inlineFunctions().
void BasicInliner::addFunction(Function *F) {
Impl->addFunction(F);
}
/// neverInlineFunction - Sometimes a function is never to be inlined because
/// of one or other reason.
void BasicInliner::neverInlineFunction(Function *F) {
Impl->neverInlineFunction(F);
}
/// inlineFuctions - Walk all call sites in all functions supplied by
/// client. Inline as many call sites as possible. Delete completely
/// inlined functions.
void BasicInliner::inlineFunctions() {
Impl->inlineFunctions();
}
}

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lib/Transforms/Utils/InlineCost.cpp Normal file
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@ -0,0 +1,241 @@
//===- InlineCoast.cpp - Cost analysis for inliner ------------------------===//
//
// 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 inline cost analysis.
//
//===----------------------------------------------------------------------===//
#include "llvm/Transforms/Utils/InlineCost.h"
#include "llvm/Support/CallSite.h"
#include "llvm/CallingConv.h"
#include "llvm/IntrinsicInst.h"
using namespace llvm;
// CountCodeReductionForConstant - Figure out an approximation for how many
// instructions will be constant folded if the specified value is constant.
//
unsigned InlineCostAnalyzer::FunctionInfo::
CountCodeReductionForConstant(Value *V) {
unsigned Reduction = 0;
for (Value::use_iterator UI = V->use_begin(), E = V->use_end(); UI != E; ++UI)
if (isa<BranchInst>(*UI))
Reduction += 40; // Eliminating a conditional branch is a big win
else if (SwitchInst *SI = dyn_cast<SwitchInst>(*UI))
// Eliminating a switch is a big win, proportional to the number of edges
// deleted.
Reduction += (SI->getNumSuccessors()-1) * 40;
else if (CallInst *CI = dyn_cast<CallInst>(*UI)) {
// Turning an indirect call into a direct call is a BIG win
Reduction += CI->getCalledValue() == V ? 500 : 0;
} else if (InvokeInst *II = dyn_cast<InvokeInst>(*UI)) {
// Turning an indirect call into a direct call is a BIG win
Reduction += II->getCalledValue() == V ? 500 : 0;
} else {
// Figure out if this instruction will be removed due to simple constant
// propagation.
Instruction &Inst = cast<Instruction>(**UI);
bool AllOperandsConstant = true;
for (unsigned i = 0, e = Inst.getNumOperands(); i != e; ++i)
if (!isa<Constant>(Inst.getOperand(i)) && Inst.getOperand(i) != V) {
AllOperandsConstant = false;
break;
}
if (AllOperandsConstant) {
// We will get to remove this instruction...
Reduction += 7;
// And any other instructions that use it which become constants
// themselves.
Reduction += CountCodeReductionForConstant(&Inst);
}
}
return Reduction;
}
// CountCodeReductionForAlloca - Figure out an approximation of how much smaller
// the function will be if it is inlined into a context where an argument
// becomes an alloca.
//
unsigned InlineCostAnalyzer::FunctionInfo::
CountCodeReductionForAlloca(Value *V) {
if (!isa<PointerType>(V->getType())) return 0; // Not a pointer
unsigned Reduction = 0;
for (Value::use_iterator UI = V->use_begin(), E = V->use_end(); UI != E;++UI){
Instruction *I = cast<Instruction>(*UI);
if (isa<LoadInst>(I) || isa<StoreInst>(I))
Reduction += 10;
else if (GetElementPtrInst *GEP = dyn_cast<GetElementPtrInst>(I)) {
// If the GEP has variable indices, we won't be able to do much with it.
for (Instruction::op_iterator I = GEP->op_begin()+1, E = GEP->op_end();
I != E; ++I)
if (!isa<Constant>(*I)) return 0;
Reduction += CountCodeReductionForAlloca(GEP)+15;
} else {
// If there is some other strange instruction, we're not going to be able
// to do much if we inline this.
return 0;
}
}
return Reduction;
}
/// analyzeFunction - Fill in the current structure with information gleaned
/// from the specified function.
void InlineCostAnalyzer::FunctionInfo::analyzeFunction(Function *F) {
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 = F->begin(), E = F->end(); BB != E; ++BB) {
for (BasicBlock::const_iterator II = BB->begin(), E = BB->end();
II != E; ++II) {
if (isa<DbgInfoIntrinsic>(II)) continue; // Debug intrinsics don't count.
// Noop casts, including ptr <-> int, don't count.
if (const CastInst *CI = dyn_cast<CastInst>(II)) {
if (CI->isLosslessCast() || isa<IntToPtrInst>(CI) ||
isa<PtrToIntInst>(CI))
continue;
} else if (const GetElementPtrInst *GEPI =
dyn_cast<GetElementPtrInst>(II)) {
// If a GEP has all constant indices, it will probably be folded with
// a load/store.
bool AllConstant = true;
for (unsigned i = 1, e = GEPI->getNumOperands(); i != e; ++i)
if (!isa<ConstantInt>(GEPI->getOperand(i))) {
AllConstant = false;
break;
}
if (AllConstant) continue;
}
++NumInsts;
}
++NumBlocks;
}
this->NumBlocks = NumBlocks;
this->NumInsts = NumInsts;
// Check out all of the arguments to the function, figuring out how much
// code can be eliminated if one of the arguments is a constant.
for (Function::arg_iterator I = F->arg_begin(), E = F->arg_end(); I != E; ++I)
ArgumentWeights.push_back(ArgInfo(CountCodeReductionForConstant(I),
CountCodeReductionForAlloca(I)));
}
// getInlineCost - The heuristic used to determine if we should inline the
// function call or not.
//
int InlineCostAnalyzer::getInlineCost(CallSite CS, std::set<const Function *> &NeverInline) {
Instruction *TheCall = CS.getInstruction();
Function *Callee = CS.getCalledFunction();
const Function *Caller = TheCall->getParent()->getParent();
// Don't inline a directly recursive call.
if (Caller == Callee ||
// Don't inline functions which can be redefined at link-time to mean
// something else. link-once linkage is ok though.
Callee->hasWeakLinkage() ||
// Don't inline functions marked noinline.
NeverInline.count(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;
// If this function uses the coldcc calling convention, prefer not to inline
// it.
if (Callee->getCallingConv() == CallingConv::Cold)
InlineCost += 2000;
// If the instruction after the call, or if the normal destination of the
// invoke is an unreachable instruction, the function is noreturn. As such,
// there is little point in inlining this.
if (InvokeInst *II = dyn_cast<InvokeInst>(TheCall)) {
if (isa<UnreachableInst>(II->getNormalDest()->begin()))
InlineCost += 10000;
} else if (isa<UnreachableInst>(++BasicBlock::iterator(TheCall)))
InlineCost += 10000;
// Get information about the callee...
FunctionInfo &CalleeFI = CachedFunctionInfo[Callee];
// If we haven't calculated this information yet, do so now.
if (CalleeFI.NumBlocks == 0)
CalleeFI.analyzeFunction(Callee);
// 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.
//
unsigned ArgNo = 0;
for (CallSite::arg_iterator I = CS.arg_begin(), E = CS.arg_end();
I != E; ++I, ++ArgNo) {
// 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 an alloca is passed in, inlining this function is likely to allow
// significant future optimization possibilities (like scalar promotion, and
// scalarization), so encourage the inlining of the function.
//
else if (isa<AllocaInst>(I)) {
if (ArgNo < CalleeFI.ArgumentWeights.size())
InlineCost -= CalleeFI.ArgumentWeights[ArgNo].AllocaWeight;
// If this is a constant being passed into the function, use the argument
// weights calculated for the callee to determine how much will be folded
// away with this information.
} else if (isa<Constant>(I)) {
if (ArgNo < CalleeFI.ArgumentWeights.size())
InlineCost -= CalleeFI.ArgumentWeights[ArgNo].ConstantWeight;
}
}
// 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.
// 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()/20;
// Look at the size of the callee. Each basic block counts as 20 units, and
// each instruction counts as 5.
InlineCost += CalleeFI.NumInsts*5 + CalleeFI.NumBlocks*20;
return InlineCost;
}