llvm-6502/include/llvm/Transforms/Utils/InlineCost.h
Daniel Dunbar c5e1ec47c7 Add InlineCost class for represent the estimated cost of inlining a
function.
 - This explicitly models the costs for functions which should
   "always" or "never" be inlined. This fixes bugs where such costs
   were not previously respected.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@58450 91177308-0d34-0410-b5e6-96231b3b80d8
2008-10-30 19:26:59 +00:00

132 lines
4.4 KiB
C++

//===- InlineCost.cpp - Cost analysis for inliner ---------------*- C++ -*-===//
//
// The LLVM Compiler Infrastructure
//
// This file is distributed under the University of Illinois Open Source
// License. See LICENSE.TXT for details.
//
//===----------------------------------------------------------------------===//
//
// This file implements heuristics for inlining decisions.
//
//===----------------------------------------------------------------------===//
#ifndef LLVM_TRANSFORMS_UTILS_INLINECOST_H
#define LLVM_TRANSFORMS_UTILS_INLINECOST_H
#include "llvm/ADT/SmallPtrSet.h"
#include <cassert>
#include <map>
#include <vector>
namespace llvm {
class Value;
class Function;
class CallSite;
/// InlineCost - Represent the cost of inlining a function. This
/// supports special values for functions which should "always" or
/// "never" be inlined. Otherwise, the cost represents a unitless
/// amount; smaller values increase the likelyhood of the function
/// being inlined.
class InlineCost {
enum Kind {
Value,
Always,
Never
};
int Cost : 30;
unsigned Type : 2;
InlineCost(int C, int T) : Cost(C), Type(T) {
assert(Cost == C && "Cost exceeds InlineCost precision");
}
public:
static InlineCost get(int Cost) { return InlineCost(Cost, Value); }
static InlineCost getAlways() { return InlineCost(0, Always); }
static InlineCost getNever() { return InlineCost(0, Never); }
bool isVariable() const { return Type == Value; }
bool isAlways() const { return Type == Always; }
bool isNever() const { return Type == Never; }
/// getValue() - Return a "variable" inline cost's amount. It is
/// an error to call this on an "always" or "never" InlineCost.
int getValue() const {
assert(Type == Value && "Invalid access of InlineCost");
return Cost;
}
};
/// 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 {
/// NeverInline - True if this callee should never be inlined into a
/// caller.
bool NeverInline;
/// 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;
/// NumVectorInsts - Keep track of how many instructions produce vector
/// values. The inliner is being more aggressive with inlining vector
/// kernels.
unsigned NumVectorInsts;
/// 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() : NeverInline(false), NumInsts(0), NumBlocks(0),
NumVectorInsts(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.
///
InlineCost getInlineCost(CallSite CS,
SmallPtrSet<const Function *, 16> &NeverInline);
/// getInlineFudgeFactor - Return a > 1.0 factor if the inliner should use a
/// higher threshold to determine if the function call should be inlined.
float getInlineFudgeFactor(CallSite CS);
};
}
#endif