llvm-6502/include/llvm/Analysis/InlineCost.h
Chandler Carruth d5003cafd6 A pile of long over-due refactorings here. There are some very, *very*
minor behavior changes with this, but nothing I have seen evidence of in
the wild or expect to be meaningful. The real goal is unifying our logic
and simplifying the interfaces. A summary of the changes follows:

- Make 'callIsSmall' actually accept a callsite so it can handle
  intrinsics, and simplify callers appropriately.
- Nuke a completely bogus declaration of 'callIsSmall' that was still
  lurking in InlineCost.h... No idea how this got missed.
- Teach the 'isInstructionFree' about the various more intelligent
  'free' heuristics that got added to the inline cost analysis during
  review and testing. This mostly surrounds int->ptr and ptr->int casts.
- Switch most of the interesting parts of the inline cost analysis that
  were essentially computing 'is this instruction free?' to use the code
  metrics routine instead. This way we won't keep duplicating logic.

All of this is motivated by the desire to allow other passes to compute
a roughly equivalent 'cost' metric for a particular basic block as the
inline cost analysis. Sadly, re-using the same analysis for both is
really messy because only the actual inline cost analysis is ever going
to go to the contortions required for simplification, SROA analysis,
etc.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@156140 91177308-0d34-0410-b5e6-96231b3b80d8
2012-05-04 00:58:03 +00:00

133 lines
4.6 KiB
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//===- InlineCost.h - 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_ANALYSIS_INLINECOST_H
#define LLVM_ANALYSIS_INLINECOST_H
#include "llvm/Function.h"
#include "llvm/ADT/DenseMap.h"
#include "llvm/ADT/SmallPtrSet.h"
#include "llvm/ADT/ValueMap.h"
#include "llvm/Analysis/CodeMetrics.h"
#include <cassert>
#include <climits>
#include <vector>
namespace llvm {
class CallSite;
class TargetData;
namespace InlineConstants {
// Various magic constants used to adjust heuristics.
const int InstrCost = 5;
const int IndirectCallThreshold = 100;
const int CallPenalty = 25;
const int LastCallToStaticBonus = -15000;
const int ColdccPenalty = 2000;
const int NoreturnPenalty = 10000;
}
/// \brief Represents 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 likelihood of the function being inlined.
///
/// Objects of this type also provide the adjusted threshold for inlining
/// based on the information available for a particular callsite. They can be
/// directly tested to determine if inlining should occur given the cost and
/// threshold for this cost metric.
class InlineCost {
enum SentinelValues {
AlwaysInlineCost = INT_MIN,
NeverInlineCost = INT_MAX
};
/// \brief The estimated cost of inlining this callsite.
const int Cost;
/// \brief The adjusted threshold against which this cost was computed.
const int Threshold;
// Trivial constructor, interesting logic in the factory functions below.
InlineCost(int Cost, int Threshold)
: Cost(Cost), Threshold(Threshold) {}
public:
static InlineCost get(int Cost, int Threshold) {
assert(Cost > AlwaysInlineCost && "Cost crosses sentinel value");
assert(Cost < NeverInlineCost && "Cost crosses sentinel value");
return InlineCost(Cost, Threshold);
}
static InlineCost getAlways() {
return InlineCost(AlwaysInlineCost, 0);
}
static InlineCost getNever() {
return InlineCost(NeverInlineCost, 0);
}
/// \brief Test whether the inline cost is low enough for inlining.
operator bool() const {
return Cost < Threshold;
}
bool isAlways() const { return Cost == AlwaysInlineCost; }
bool isNever() const { return Cost == NeverInlineCost; }
bool isVariable() const { return !isAlways() && !isNever(); }
/// \brief Get the inline cost estimate.
/// It is an error to call this on an "always" or "never" InlineCost.
int getCost() const {
assert(isVariable() && "Invalid access of InlineCost");
return Cost;
}
/// \brief Get the cost delta from the threshold for inlining.
/// Only valid if the cost is of the variable kind. Returns a negative
/// value if the cost is too high to inline.
int getCostDelta() const { return Threshold - getCost(); }
};
/// InlineCostAnalyzer - Cost analyzer used by inliner.
class InlineCostAnalyzer {
// TargetData if available, or null.
const TargetData *TD;
public:
InlineCostAnalyzer(): TD(0) {}
void setTargetData(const TargetData *TData) { TD = TData; }
/// \brief Get an InlineCost object representing the cost of inlining this
/// callsite.
///
/// Note that threshold is passed into this function. Only costs below the
/// threshold are computed with any accuracy. The threshold can be used to
/// bound the computation necessary to determine whether the cost is
/// sufficiently low to warrant inlining.
InlineCost getInlineCost(CallSite CS, int Threshold);
/// getCalledFunction - The heuristic used to determine if we should inline
/// the function call or not. The callee is explicitly specified, to allow
/// you to calculate the cost of inlining a function via a pointer. This
/// behaves exactly as the version with no explicit callee parameter in all
/// other respects.
//
// Note: This is used by out-of-tree passes, please do not remove without
// adding a replacement API.
InlineCost getInlineCost(CallSite CS, Function *Callee, int Threshold);
};
}
#endif