LLVM 17.0.0git
InlineCost.h
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1//===- InlineCost.h - Cost analysis for inliner -----------------*- C++ -*-===//
2//
3// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
4// See https://llvm.org/LICENSE.txt for license information.
5// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
6//
7//===----------------------------------------------------------------------===//
8//
9// This file implements heuristics for inlining decisions.
10//
11//===----------------------------------------------------------------------===//
12
13#ifndef LLVM_ANALYSIS_INLINECOST_H
14#define LLVM_ANALYSIS_INLINECOST_H
15
16#include "llvm/ADT/APInt.h"
19#include "llvm/IR/PassManager.h"
20#include <cassert>
21#include <climits>
22#include <optional>
23
24namespace llvm {
25class AssumptionCache;
26class OptimizationRemarkEmitter;
27class BlockFrequencyInfo;
28class CallBase;
29class DataLayout;
30class Function;
31class ProfileSummaryInfo;
32class TargetTransformInfo;
33class TargetLibraryInfo;
34
35namespace InlineConstants {
36// Various thresholds used by inline cost analysis.
37/// Use when optsize (-Os) is specified.
38const int OptSizeThreshold = 50;
39
40/// Use when minsize (-Oz) is specified.
41const int OptMinSizeThreshold = 5;
42
43/// Use when -O3 is specified.
44const int OptAggressiveThreshold = 250;
45
46// Various magic constants used to adjust heuristics.
47int getInstrCost();
48const int IndirectCallThreshold = 100;
49const int LoopPenalty = 25;
50const int LastCallToStaticBonus = 15000;
51const int ColdccPenalty = 2000;
52/// Do not inline functions which allocate this many bytes on the stack
53/// when the caller is recursive.
54const unsigned TotalAllocaSizeRecursiveCaller = 1024;
55/// Do not inline dynamic allocas that have been constant propagated to be
56/// static allocas above this amount in bytes.
58
60 "function-inline-cost-multiplier";
61
62const char MaxInlineStackSizeAttributeName[] = "inline-max-stacksize";
63} // namespace InlineConstants
64
65// The cost-benefit pair computed by cost-benefit analysis.
67public:
68 CostBenefitPair(APInt Cost, APInt Benefit) : Cost(Cost), Benefit(Benefit) {}
69
70 const APInt &getCost() const { return Cost; }
71
72 const APInt &getBenefit() const { return Benefit; }
73
74private:
75 APInt Cost;
76 APInt Benefit;
77};
78
79/// Represents the cost of inlining a function.
80///
81/// This supports special values for functions which should "always" or
82/// "never" be inlined. Otherwise, the cost represents a unitless amount;
83/// smaller values increase the likelihood of the function being inlined.
84///
85/// Objects of this type also provide the adjusted threshold for inlining
86/// based on the information available for a particular callsite. They can be
87/// directly tested to determine if inlining should occur given the cost and
88/// threshold for this cost metric.
90 enum SentinelValues { AlwaysInlineCost = INT_MIN, NeverInlineCost = INT_MAX };
91
92 /// The estimated cost of inlining this callsite.
93 int Cost = 0;
94
95 /// The adjusted threshold against which this cost was computed.
96 int Threshold = 0;
97
98 /// The amount of StaticBonus that has been applied.
99 int StaticBonusApplied = 0;
100
101 /// Must be set for Always and Never instances.
102 const char *Reason = nullptr;
103
104 /// The cost-benefit pair computed by cost-benefit analysis.
105 std::optional<CostBenefitPair> CostBenefit;
106
107 // Trivial constructor, interesting logic in the factory functions below.
108 InlineCost(int Cost, int Threshold, int StaticBonusApplied,
109 const char *Reason = nullptr,
110 std::optional<CostBenefitPair> CostBenefit = std::nullopt)
111 : Cost(Cost), Threshold(Threshold),
112 StaticBonusApplied(StaticBonusApplied), Reason(Reason),
114 assert((isVariable() || Reason) &&
115 "Reason must be provided for Never or Always");
116 }
117
118public:
119 static InlineCost get(int Cost, int Threshold, int StaticBonus = 0) {
120 assert(Cost > AlwaysInlineCost && "Cost crosses sentinel value");
121 assert(Cost < NeverInlineCost && "Cost crosses sentinel value");
122 return InlineCost(Cost, Threshold, StaticBonus);
123 }
124 static InlineCost
125 getAlways(const char *Reason,
126 std::optional<CostBenefitPair> CostBenefit = std::nullopt) {
127 return InlineCost(AlwaysInlineCost, 0, 0, Reason, CostBenefit);
128 }
129 static InlineCost
130 getNever(const char *Reason,
131 std::optional<CostBenefitPair> CostBenefit = std::nullopt) {
132 return InlineCost(NeverInlineCost, 0, 0, Reason, CostBenefit);
133 }
134
135 /// Test whether the inline cost is low enough for inlining.
136 explicit operator bool() const { return Cost < Threshold; }
137
138 bool isAlways() const { return Cost == AlwaysInlineCost; }
139 bool isNever() const { return Cost == NeverInlineCost; }
140 bool isVariable() const { return !isAlways() && !isNever(); }
141
142 /// Get the inline cost estimate.
143 /// It is an error to call this on an "always" or "never" InlineCost.
144 int getCost() const {
145 assert(isVariable() && "Invalid access of InlineCost");
146 return Cost;
147 }
148
149 /// Get the threshold against which the cost was computed
150 int getThreshold() const {
151 assert(isVariable() && "Invalid access of InlineCost");
152 return Threshold;
153 }
154
155 /// Get the amount of StaticBonus applied.
157 assert(isVariable() && "Invalid access of InlineCost");
158 return StaticBonusApplied;
159 }
160
161 /// Get the cost-benefit pair which was computed by cost-benefit analysis
162 std::optional<CostBenefitPair> getCostBenefit() const { return CostBenefit; }
163
164 /// Get the reason of Always or Never.
165 const char *getReason() const {
166 assert((Reason || isVariable()) &&
167 "InlineCost reason must be set for Always or Never");
168 return Reason;
169 }
170
171 /// Get the cost delta from the threshold for inlining.
172 /// Only valid if the cost is of the variable kind. Returns a negative
173 /// value if the cost is too high to inline.
174 int getCostDelta() const { return Threshold - getCost(); }
175};
176
177/// InlineResult is basically true or false. For false results the message
178/// describes a reason.
180 const char *Message = nullptr;
181 InlineResult(const char *Message = nullptr) : Message(Message) {}
182
183public:
184 static InlineResult success() { return {}; }
185 static InlineResult failure(const char *Reason) {
186 return InlineResult(Reason);
187 }
188 bool isSuccess() const { return Message == nullptr; }
189 const char *getFailureReason() const {
190 assert(!isSuccess() &&
191 "getFailureReason should only be called in failure cases");
192 return Message;
193 }
194};
195
196/// Thresholds to tune inline cost analysis. The inline cost analysis decides
197/// the condition to apply a threshold and applies it. Otherwise,
198/// DefaultThreshold is used. If a threshold is Optional, it is applied only
199/// when it has a valid value. Typically, users of inline cost analysis
200/// obtain an InlineParams object through one of the \c getInlineParams methods
201/// and pass it to \c getInlineCost. Some specialized versions of inliner
202/// (such as the pre-inliner) might have custom logic to compute \c InlineParams
203/// object.
204
206 /// The default threshold to start with for a callee.
208
209 /// Threshold to use for callees with inline hint.
210 std::optional<int> HintThreshold;
211
212 /// Threshold to use for cold callees.
213 std::optional<int> ColdThreshold;
214
215 /// Threshold to use when the caller is optimized for size.
216 std::optional<int> OptSizeThreshold;
217
218 /// Threshold to use when the caller is optimized for minsize.
219 std::optional<int> OptMinSizeThreshold;
220
221 /// Threshold to use when the callsite is considered hot.
222 std::optional<int> HotCallSiteThreshold;
223
224 /// Threshold to use when the callsite is considered hot relative to function
225 /// entry.
226 std::optional<int> LocallyHotCallSiteThreshold;
227
228 /// Threshold to use when the callsite is considered cold.
229 std::optional<int> ColdCallSiteThreshold;
230
231 /// Compute inline cost even when the cost has exceeded the threshold.
232 std::optional<bool> ComputeFullInlineCost;
233
234 /// Indicate whether we should allow inline deferral.
235 std::optional<bool> EnableDeferral;
236
237 /// Indicate whether we allow inlining for recursive call.
238 std::optional<bool> AllowRecursiveCall = false;
239};
240
241std::optional<int> getStringFnAttrAsInt(CallBase &CB, StringRef AttrKind);
242
243/// Generate the parameters to tune the inline cost analysis based only on the
244/// commandline options.
246
247/// Generate the parameters to tune the inline cost analysis based on command
248/// line options. If -inline-threshold option is not explicitly passed,
249/// \p Threshold is used as the default threshold.
250InlineParams getInlineParams(int Threshold);
251
252/// Generate the parameters to tune the inline cost analysis based on command
253/// line options. If -inline-threshold option is not explicitly passed,
254/// the default threshold is computed from \p OptLevel and \p SizeOptLevel.
255/// An \p OptLevel value above 3 is considered an aggressive optimization mode.
256/// \p SizeOptLevel of 1 corresponds to the -Os flag and 2 corresponds to
257/// the -Oz flag.
258InlineParams getInlineParams(unsigned OptLevel, unsigned SizeOptLevel);
259
260/// Return the cost associated with a callsite, including parameter passing
261/// and the call/return instruction.
262int getCallsiteCost(const CallBase &Call, const DataLayout &DL);
263
264/// Get an InlineCost object representing the cost of inlining this
265/// callsite.
266///
267/// Note that a default threshold is passed into this function. This threshold
268/// could be modified based on callsite's properties and only costs below this
269/// new threshold are computed with any accuracy. The new threshold can be
270/// used to bound the computation necessary to determine whether the cost is
271/// sufficiently low to warrant inlining.
272///
273/// Also note that calling this function *dynamically* computes the cost of
274/// inlining the callsite. It is an expensive, heavyweight call.
276getInlineCost(CallBase &Call, const InlineParams &Params,
277 TargetTransformInfo &CalleeTTI,
278 function_ref<AssumptionCache &(Function &)> GetAssumptionCache,
279 function_ref<const TargetLibraryInfo &(Function &)> GetTLI,
280 function_ref<BlockFrequencyInfo &(Function &)> GetBFI = nullptr,
281 ProfileSummaryInfo *PSI = nullptr,
282 OptimizationRemarkEmitter *ORE = nullptr);
283
284/// Get an InlineCost with the callee explicitly specified.
285/// This allows you to calculate the cost of inlining a function via a
286/// pointer. This behaves exactly as the version with no explicit callee
287/// parameter in all other respects.
288//
290getInlineCost(CallBase &Call, Function *Callee, const InlineParams &Params,
291 TargetTransformInfo &CalleeTTI,
292 function_ref<AssumptionCache &(Function &)> GetAssumptionCache,
293 function_ref<const TargetLibraryInfo &(Function &)> GetTLI,
294 function_ref<BlockFrequencyInfo &(Function &)> GetBFI = nullptr,
295 ProfileSummaryInfo *PSI = nullptr,
296 OptimizationRemarkEmitter *ORE = nullptr);
297
298/// Returns InlineResult::success() if the call site should be always inlined
299/// because of user directives, and the inlining is viable. Returns
300/// InlineResult::failure() if the inlining may never happen because of user
301/// directives or incompatibilities detectable without needing callee traversal.
302/// Otherwise returns std::nullopt, meaning that inlining should be decided
303/// based on other criteria (e.g. cost modeling).
304std::optional<InlineResult> getAttributeBasedInliningDecision(
305 CallBase &Call, Function *Callee, TargetTransformInfo &CalleeTTI,
306 function_ref<const TargetLibraryInfo &(Function &)> GetTLI);
307
308/// Get the cost estimate ignoring thresholds. This is similar to getInlineCost
309/// when passed InlineParams::ComputeFullInlineCost, or a non-null ORE. It
310/// uses default InlineParams otherwise.
311/// Contrary to getInlineCost, which makes a threshold-based final evaluation of
312/// should/shouldn't inline, captured in InlineResult, getInliningCostEstimate
313/// returns:
314/// - std::nullopt, if the inlining cannot happen (is illegal)
315/// - an integer, representing the cost.
316std::optional<int> getInliningCostEstimate(
317 CallBase &Call, TargetTransformInfo &CalleeTTI,
318 function_ref<AssumptionCache &(Function &)> GetAssumptionCache,
319 function_ref<BlockFrequencyInfo &(Function &)> GetBFI = nullptr,
320 ProfileSummaryInfo *PSI = nullptr,
321 OptimizationRemarkEmitter *ORE = nullptr);
322
323/// Get the expanded cost features. The features are returned unconditionally,
324/// even if inlining is impossible.
325std::optional<InlineCostFeatures> getInliningCostFeatures(
326 CallBase &Call, TargetTransformInfo &CalleeTTI,
327 function_ref<AssumptionCache &(Function &)> GetAssumptionCache,
328 function_ref<BlockFrequencyInfo &(Function &)> GetBFI = nullptr,
329 ProfileSummaryInfo *PSI = nullptr,
330 OptimizationRemarkEmitter *ORE = nullptr);
331
332/// Minimal filter to detect invalid constructs for inlining.
334
335// This pass is used to annotate instructions during the inline process for
336// debugging and analysis. The main purpose of the pass is to see and test
337// inliner's decisions when creating new optimizations to InlineCost.
339 : PassInfoMixin<InlineCostAnnotationPrinterPass> {
341
342public:
345};
346} // namespace llvm
347
348#endif
MachineBasicBlock MachineBasicBlock::iterator DebugLoc DL
amdgpu Simplify well known AMD library false FunctionCallee Callee
This file implements a class to represent arbitrary precision integral constant values and operations...
#define F(x, y, z)
Definition: MD5.cpp:55
FunctionAnalysisManager FAM
This header defines various interfaces for pass management in LLVM.
assert(ImpDefSCC.getReg()==AMDGPU::SCC &&ImpDefSCC.isDef())
Class for arbitrary precision integers.
Definition: APInt.h:75
A container for analyses that lazily runs them and caches their results.
Definition: PassManager.h:620
A cache of @llvm.assume calls within a function.
BlockFrequencyInfo pass uses BlockFrequencyInfoImpl implementation to estimate IR basic block frequen...
Base class for all callable instructions (InvokeInst and CallInst) Holds everything related to callin...
Definition: InstrTypes.h:1184
const APInt & getBenefit() const
Definition: InlineCost.h:72
CostBenefitPair(APInt Cost, APInt Benefit)
Definition: InlineCost.h:68
const APInt & getCost() const
Definition: InlineCost.h:70
A parsed version of the target data layout string in and methods for querying it.
Definition: DataLayout.h:114
Represents the cost of inlining a function.
Definition: InlineCost.h:89
std::optional< CostBenefitPair > getCostBenefit() const
Get the cost-benefit pair which was computed by cost-benefit analysis.
Definition: InlineCost.h:162
int getThreshold() const
Get the threshold against which the cost was computed.
Definition: InlineCost.h:150
const char * getReason() const
Get the reason of Always or Never.
Definition: InlineCost.h:165
int getStaticBonusApplied() const
Get the amount of StaticBonus applied.
Definition: InlineCost.h:156
int getCost() const
Get the inline cost estimate.
Definition: InlineCost.h:144
static InlineCost getNever(const char *Reason, std::optional< CostBenefitPair > CostBenefit=std::nullopt)
Definition: InlineCost.h:130
static InlineCost getAlways(const char *Reason, std::optional< CostBenefitPair > CostBenefit=std::nullopt)
Definition: InlineCost.h:125
static InlineCost get(int Cost, int Threshold, int StaticBonus=0)
Definition: InlineCost.h:119
bool isAlways() const
Definition: InlineCost.h:138
int getCostDelta() const
Get the cost delta from the threshold for inlining.
Definition: InlineCost.h:174
bool isVariable() const
Definition: InlineCost.h:140
bool isNever() const
Definition: InlineCost.h:139
InlineResult is basically true or false.
Definition: InlineCost.h:179
static InlineResult success()
Definition: InlineCost.h:184
static InlineResult failure(const char *Reason)
Definition: InlineCost.h:185
bool isSuccess() const
Definition: InlineCost.h:188
const char * getFailureReason() const
Definition: InlineCost.h:189
The optimization diagnostic interface.
A set of analyses that are preserved following a run of a transformation pass.
Definition: PassManager.h:152
Analysis providing profile information.
StringRef - Represent a constant reference to a string, i.e.
Definition: StringRef.h:50
Provides information about what library functions are available for the current target.
This pass provides access to the codegen interfaces that are needed for IR-level transformations.
An efficient, type-erasing, non-owning reference to a callable.
This class implements an extremely fast bulk output stream that can only output to a stream.
Definition: raw_ostream.h:52
const int ColdccPenalty
Definition: InlineCost.h:51
const char FunctionInlineCostMultiplierAttributeName[]
Definition: InlineCost.h:59
const int OptSizeThreshold
Use when optsize (-Os) is specified.
Definition: InlineCost.h:38
const int OptMinSizeThreshold
Use when minsize (-Oz) is specified.
Definition: InlineCost.h:41
const int LoopPenalty
Definition: InlineCost.h:49
const uint64_t MaxSimplifiedDynamicAllocaToInline
Do not inline dynamic allocas that have been constant propagated to be static allocas above this amou...
Definition: InlineCost.h:57
const int IndirectCallThreshold
Definition: InlineCost.h:48
const int OptAggressiveThreshold
Use when -O3 is specified.
Definition: InlineCost.h:44
const char MaxInlineStackSizeAttributeName[]
Definition: InlineCost.h:62
const int LastCallToStaticBonus
Definition: InlineCost.h:50
const unsigned TotalAllocaSizeRecursiveCaller
Do not inline functions which allocate this many bytes on the stack when the caller is recursive.
Definition: InlineCost.h:54
This is an optimization pass for GlobalISel generic memory operations.
Definition: AddressRanges.h:18
std::optional< int > getStringFnAttrAsInt(CallBase &CB, StringRef AttrKind)
Definition: InlineCost.cpp:175
int getCallsiteCost(const CallBase &Call, const DataLayout &DL)
Return the cost associated with a callsite, including parameter passing and the call/return instructi...
std::optional< InlineCostFeatures > getInliningCostFeatures(CallBase &Call, TargetTransformInfo &CalleeTTI, function_ref< AssumptionCache &(Function &)> GetAssumptionCache, function_ref< BlockFrequencyInfo &(Function &)> GetBFI=nullptr, ProfileSummaryInfo *PSI=nullptr, OptimizationRemarkEmitter *ORE=nullptr)
Get the expanded cost features.
InlineResult isInlineViable(Function &Callee)
Minimal filter to detect invalid constructs for inlining.
InlineCost getInlineCost(CallBase &Call, const InlineParams &Params, TargetTransformInfo &CalleeTTI, function_ref< AssumptionCache &(Function &)> GetAssumptionCache, function_ref< const TargetLibraryInfo &(Function &)> GetTLI, function_ref< BlockFrequencyInfo &(Function &)> GetBFI=nullptr, ProfileSummaryInfo *PSI=nullptr, OptimizationRemarkEmitter *ORE=nullptr)
Get an InlineCost object representing the cost of inlining this callsite.
std::optional< InlineResult > getAttributeBasedInliningDecision(CallBase &Call, Function *Callee, TargetTransformInfo &CalleeTTI, function_ref< const TargetLibraryInfo &(Function &)> GetTLI)
Returns InlineResult::success() if the call site should be always inlined because of user directives,...
InlineParams getInlineParams()
Generate the parameters to tune the inline cost analysis based only on the commandline options.
std::optional< int > getInliningCostEstimate(CallBase &Call, TargetTransformInfo &CalleeTTI, function_ref< AssumptionCache &(Function &)> GetAssumptionCache, function_ref< BlockFrequencyInfo &(Function &)> GetBFI=nullptr, ProfileSummaryInfo *PSI=nullptr, OptimizationRemarkEmitter *ORE=nullptr)
Get the cost estimate ignoring thresholds.
PreservedAnalyses run(Function &F, FunctionAnalysisManager &FAM)
InlineCostAnnotationPrinterPass(raw_ostream &OS)
Definition: InlineCost.h:343
Thresholds to tune inline cost analysis.
Definition: InlineCost.h:205
std::optional< int > OptMinSizeThreshold
Threshold to use when the caller is optimized for minsize.
Definition: InlineCost.h:219
std::optional< int > OptSizeThreshold
Threshold to use when the caller is optimized for size.
Definition: InlineCost.h:216
std::optional< int > ColdCallSiteThreshold
Threshold to use when the callsite is considered cold.
Definition: InlineCost.h:229
std::optional< int > ColdThreshold
Threshold to use for cold callees.
Definition: InlineCost.h:213
std::optional< int > HotCallSiteThreshold
Threshold to use when the callsite is considered hot.
Definition: InlineCost.h:222
std::optional< bool > AllowRecursiveCall
Indicate whether we allow inlining for recursive call.
Definition: InlineCost.h:238
int DefaultThreshold
The default threshold to start with for a callee.
Definition: InlineCost.h:207
std::optional< bool > EnableDeferral
Indicate whether we should allow inline deferral.
Definition: InlineCost.h:235
std::optional< int > HintThreshold
Threshold to use for callees with inline hint.
Definition: InlineCost.h:210
std::optional< int > LocallyHotCallSiteThreshold
Threshold to use when the callsite is considered hot relative to function entry.
Definition: InlineCost.h:226
std::optional< bool > ComputeFullInlineCost
Compute inline cost even when the cost has exceeded the threshold.
Definition: InlineCost.h:232
A CRTP mix-in to automatically provide informational APIs needed for passes.
Definition: PassManager.h:371