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9c2e0e0fa4
Summary:
Before this change the Executable function was made by duplicating the
snippet. This change adds a --repetion-mode={loop|duplicate} flag that
allows choosing between this behaviour and wrapping the snippet instructions
in a loop.
The new mode can help measurements when the snippet fits in the DSB by
short-cirtcuiting decoding. The loop adds a dec + jmp to the measurements, but
since these are not part of the critical path, they execute in parallel
with the measured code and do not impact measurements in practice.
Overview of the change:
- New SnippetRepetitor abstraction that handles repeating the snippet.
The assembler delegates repeating the instructions to this class.
- ExegesisTarget learns how to decrement loop counter and jump.
- Some refactoring of the assembler into FunctionFiller/BasicBlockFiller.
Reviewers: gchatelet
Subscribers: mgorny, tschuett, llvm-commits
Tags: #llvm
Differential Revision: https://reviews.llvm.org/D68125
llvm-svn: 373083
54 lines
1.6 KiB
C++
54 lines
1.6 KiB
C++
//===-- SnippetRepetitor.h --------------------------------------*- C++ -*-===//
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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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/// \file
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/// Defines helpers to fill functions with repetitions of a snippet.
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///
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//===----------------------------------------------------------------------===//
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#ifndef LLVM_TOOLS_LLVM_EXEGESIS_FUNCTIONFILLER_H
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#define LLVM_TOOLS_LLVM_EXEGESIS_FUNCTIONFILLER_H
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#include "Assembler.h"
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#include "BenchmarkResult.h"
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#include "LlvmState.h"
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#include "llvm/ADT/BitVector.h"
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#include "llvm/CodeGen/MachineFunction.h"
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#include "llvm/MC/MCInst.h"
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#include "llvm/MC/MCInstrInfo.h"
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#include "llvm/Object/Binary.h"
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namespace llvm {
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namespace exegesis {
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class SnippetRepetitor {
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public:
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static std::unique_ptr<const SnippetRepetitor>
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Create(InstructionBenchmark::RepetitionModeE Mode, const LLVMState &State);
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virtual ~SnippetRepetitor();
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// Returns the set of registers that are reserved by the repetitor.
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virtual BitVector getReservedRegs() const = 0;
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// Returns a functor that repeats `Instructions` so that the function executes
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// at least `MinInstructions` instructions.
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virtual FillFunction Repeat(ArrayRef<MCInst> Instructions,
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unsigned MinInstructions) const = 0;
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explicit SnippetRepetitor(const LLVMState &State) : State(State) {}
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protected:
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const LLVMState &State;
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};
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} // namespace exegesis
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} // namespace llvm
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#endif
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