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Instrumentation
ValueProfileCollector.h
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//===- ValueProfileCollector.h - determine what to value profile ----------===//
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//
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// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
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// See https://llvm.org/LICENSE.txt for license information.
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// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
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//
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//===----------------------------------------------------------------------===//
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//
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// This file contains a utility class, ValueProfileCollector, that is used to
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// determine what kind of llvm::Value's are worth value-profiling, at which
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// point in the program, and which instruction holds the Value Profile metadata.
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// Currently, the only users of this utility is the PGOInstrumentation[Gen|Use]
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// passes.
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//===----------------------------------------------------------------------===//
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#ifndef LLVM_ANALYSIS_PROFILE_GEN_ANALYSIS_H
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#define LLVM_ANALYSIS_PROFILE_GEN_ANALYSIS_H
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#include "
llvm/ProfileData/InstrProf.h
"
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#include <memory>
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#include <vector>
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namespace
llvm
{
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class
Function
;
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class
Instruction;
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class
TargetLibraryInfo;
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class
Value
;
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/// Utility analysis that determines what values are worth profiling.
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/// The actual logic is inside the ValueProfileCollectorImpl, whose job is to
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/// populate the Candidates vector.
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///
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/// Value profiling an expression means to track the values that this expression
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/// takes at runtime and the frequency of each value.
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/// It is important to distinguish between two sets of value profiles for a
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/// particular expression:
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/// 1) The set of values at the point of evaluation.
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/// 2) The set of values at the point of use.
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/// In some cases, the two sets are identical, but it's not unusual for the two
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/// to differ.
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///
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/// To elaborate more, consider this C code, and focus on the expression `nn`:
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/// void foo(int nn, bool b) {
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/// if (b) memcpy(x, y, nn);
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/// }
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/// The point of evaluation can be as early as the start of the function, and
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/// let's say the value profile for `nn` is:
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/// total=100; (value,freq) set = {(8,10), (32,50)}
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/// The point of use is right before we call memcpy, and since we execute the
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/// memcpy conditionally, the value profile of `nn` can be:
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/// total=15; (value,freq) set = {(8,10), (4,5)}
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///
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/// For this reason, a plugin is responsible for computing the insertion point
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/// for each value to be profiled. The `CandidateInfo` structure encapsulates
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/// all the information needed for each value profile site.
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class
ValueProfileCollector
{
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public
:
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struct
CandidateInfo
{
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Value
*
V
;
// The value to profile.
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Instruction
*
InsertPt
;
// Insert the VP lib call before this instr.
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Instruction
*
AnnotatedInst
;
// Where metadata is attached.
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};
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ValueProfileCollector
(
Function
&Fn,
TargetLibraryInfo
&TLI);
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ValueProfileCollector
(
ValueProfileCollector
&&) =
delete
;
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ValueProfileCollector
&
operator=
(
ValueProfileCollector
&&) =
delete
;
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ValueProfileCollector
(
const
ValueProfileCollector
&) =
delete
;
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ValueProfileCollector
&
operator=
(
const
ValueProfileCollector
&) =
delete
;
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~ValueProfileCollector
();
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/// returns a list of value profiling candidates of the given kind
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std::vector<CandidateInfo>
get
(
InstrProfValueKind
Kind
)
const
;
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private
:
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class
ValueProfileCollectorImpl
;
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std::unique_ptr<ValueProfileCollectorImpl> PImpl;
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};
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}
// namespace llvm
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#endif
llvm
This is an optimization pass for GlobalISel generic memory operations.
Definition:
AddressRanges.h:17
llvm::Function
Definition:
Function.h:60
llvm::ValueProfileCollector::ValueProfileCollectorImpl
ValueProfileCollectorImpl inherits the API of PluginChainFinal.
Definition:
ValueProfileCollector.cpp:61
llvm::ValueProfileCollector::~ValueProfileCollector
~ValueProfileCollector()
llvm::ValueProfileCollector::operator=
ValueProfileCollector & operator=(ValueProfileCollector &&)=delete
llvm::ValueProfileCollector::CandidateInfo::V
Value * V
Definition:
ValueProfileCollector.h:60
llvm::ValueProfileCollector::CandidateInfo::AnnotatedInst
Instruction * AnnotatedInst
Definition:
ValueProfileCollector.h:62
llvm::ValueProfileCollector::ValueProfileCollector
ValueProfileCollector(Function &Fn, TargetLibraryInfo &TLI)
Definition:
ValueProfileCollector.cpp:66
llvm::Instruction
Definition:
Instruction.h:42
InstrProf.h
llvm::lltok::Kind
Kind
Definition:
LLToken.h:18
llvm::ValueProfileCollector::CandidateInfo::InsertPt
Instruction * InsertPt
Definition:
ValueProfileCollector.h:61
llvm::InstrProfValueKind
InstrProfValueKind
Definition:
InstrProf.h:239
llvm::ValueProfileCollector
Utility analysis that determines what values are worth profiling.
Definition:
ValueProfileCollector.h:57
llvm::TargetStackID::Value
Value
Definition:
TargetFrameLowering.h:27
llvm::ValueProfileCollector::CandidateInfo
Definition:
ValueProfileCollector.h:59
llvm::TargetLibraryInfo
Provides information about what library functions are available for the current target.
Definition:
TargetLibraryInfo.h:222
llvm::Value
LLVM Value Representation.
Definition:
Value.h:74
llvm::ValueProfileCollector::get
std::vector< CandidateInfo > get(InstrProfValueKind Kind) const
returns a list of value profiling candidates of the given kind
Definition:
ValueProfileCollector.cpp:73
llvm::codeview::PublicSymFlags::Function
@ Function
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