181 lines
6.0 KiB
C++
181 lines
6.0 KiB
C++
//===- InlineCost.cpp - Cost analysis for inliner ---------------*- C++ -*-===//
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//
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// The LLVM Compiler Infrastructure
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//
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// This file is distributed under the University of Illinois Open Source
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// License. See LICENSE.TXT for details.
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//
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//===----------------------------------------------------------------------===//
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//
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// This file implements heuristics for inlining decisions.
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//
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//===----------------------------------------------------------------------===//
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#ifndef LLVM_ANALYSIS_INLINECOST_H
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#define LLVM_ANALYSIS_INLINECOST_H
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#include <cassert>
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#include <climits>
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#include <map>
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#include <vector>
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namespace llvm {
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class Value;
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class Function;
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class BasicBlock;
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class CallSite;
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template<class PtrType, unsigned SmallSize>
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class SmallPtrSet;
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// CodeMetrics - Calculate size and a few similar metrics for a set of
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// basic blocks.
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struct CodeMetrics {
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/// NeverInline - True if this callee should never be inlined into a
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/// caller.
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bool NeverInline;
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/// usesDynamicAlloca - True if this function calls alloca (in the C sense).
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bool usesDynamicAlloca;
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/// NumInsts, NumBlocks - Keep track of how large each function is, which
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/// is used to estimate the code size cost of inlining it.
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unsigned NumInsts, NumBlocks;
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/// NumVectorInsts - Keep track of how many instructions produce vector
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/// values. The inliner is being more aggressive with inlining vector
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/// kernels.
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unsigned NumVectorInsts;
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/// NumRets - Keep track of how many Ret instructions the block contains.
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unsigned NumRets;
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CodeMetrics() : NeverInline(false), usesDynamicAlloca(false), NumInsts(0),
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NumBlocks(0), NumVectorInsts(0), NumRets(0) {}
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/// analyzeBasicBlock - Add information about the specified basic block
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/// to the current structure.
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void analyzeBasicBlock(const BasicBlock *BB);
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/// analyzeFunction - Add information about the specified function
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/// to the current structure.
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void analyzeFunction(Function *F);
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};
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namespace InlineConstants {
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// Various magic constants used to adjust heuristics.
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const int CallPenalty = 5;
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const int LastCallToStaticBonus = -15000;
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const int ColdccPenalty = 2000;
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const int NoreturnPenalty = 10000;
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}
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/// InlineCost - Represent the cost of inlining a function. This
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/// supports special values for functions which should "always" or
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/// "never" be inlined. Otherwise, the cost represents a unitless
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/// amount; smaller values increase the likelyhood of the function
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/// being inlined.
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class InlineCost {
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enum Kind {
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Value,
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Always,
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Never
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};
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// This is a do-it-yourself implementation of
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// int Cost : 30;
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// unsigned Type : 2;
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// We used to use bitfields, but they were sometimes miscompiled (PR3822).
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enum { TYPE_BITS = 2 };
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enum { COST_BITS = unsigned(sizeof(unsigned)) * CHAR_BIT - TYPE_BITS };
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unsigned TypedCost; // int Cost : COST_BITS; unsigned Type : TYPE_BITS;
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Kind getType() const {
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return Kind(TypedCost >> COST_BITS);
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}
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int getCost() const {
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// Sign-extend the bottom COST_BITS bits.
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return (int(TypedCost << TYPE_BITS)) >> TYPE_BITS;
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}
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InlineCost(int C, int T) {
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TypedCost = (unsigned(C << TYPE_BITS) >> TYPE_BITS) | (T << COST_BITS);
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assert(getCost() == C && "Cost exceeds InlineCost precision");
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}
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public:
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static InlineCost get(int Cost) { return InlineCost(Cost, Value); }
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static InlineCost getAlways() { return InlineCost(0, Always); }
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static InlineCost getNever() { return InlineCost(0, Never); }
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bool isVariable() const { return getType() == Value; }
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bool isAlways() const { return getType() == Always; }
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bool isNever() const { return getType() == Never; }
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/// getValue() - Return a "variable" inline cost's amount. It is
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/// an error to call this on an "always" or "never" InlineCost.
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int getValue() const {
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assert(getType() == Value && "Invalid access of InlineCost");
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return getCost();
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}
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};
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/// InlineCostAnalyzer - Cost analyzer used by inliner.
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class InlineCostAnalyzer {
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struct ArgInfo {
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public:
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unsigned ConstantWeight;
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unsigned AllocaWeight;
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ArgInfo(unsigned CWeight, unsigned AWeight)
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: ConstantWeight(CWeight), AllocaWeight(AWeight) {}
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};
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struct FunctionInfo {
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CodeMetrics Metrics;
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/// ArgumentWeights - Each formal argument of the function is inspected to
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/// see if it is used in any contexts where making it a constant or alloca
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/// would reduce the code size. If so, we add some value to the argument
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/// entry here.
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std::vector<ArgInfo> ArgumentWeights;
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/// CountCodeReductionForConstant - Figure out an approximation for how
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/// many instructions will be constant folded if the specified value is
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/// constant.
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unsigned CountCodeReductionForConstant(Value *V);
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/// CountCodeReductionForAlloca - Figure out an approximation of how much
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/// smaller the function will be if it is inlined into a context where an
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/// argument becomes an alloca.
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///
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unsigned CountCodeReductionForAlloca(Value *V);
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/// analyzeFunction - Add information about the specified function
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/// to the current structure.
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void analyzeFunction(Function *F);
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};
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std::map<const Function *, FunctionInfo> CachedFunctionInfo;
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public:
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/// getInlineCost - The heuristic used to determine if we should inline the
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/// function call or not.
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///
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InlineCost getInlineCost(CallSite CS,
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SmallPtrSet<const Function *, 16> &NeverInline);
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/// getInlineFudgeFactor - Return a > 1.0 factor if the inliner should use a
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/// higher threshold to determine if the function call should be inlined.
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float getInlineFudgeFactor(CallSite CS);
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/// resetCachedFunctionInfo - erase any cached cost info for this function.
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void resetCachedCostInfo(Function* Caller) {
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CachedFunctionInfo[Caller] = FunctionInfo();
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}
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};
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}
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#endif
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