1//===-- SnippetGenerator.h --------------------------------------*- 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/// \file
10/// Defines the abstract SnippetGenerator class for generating code that allows
11/// measuring a certain property of instructions (e.g. latency).
12///
13//===----------------------------------------------------------------------===//
14
15#ifndef LLVM_TOOLS_LLVM_EXEGESIS_SNIPPETGENERATOR_H
16#define LLVM_TOOLS_LLVM_EXEGESIS_SNIPPETGENERATOR_H
17
18#include "Assembler.h"
19#include "BenchmarkCode.h"
20#include "CodeTemplate.h"
21#include "LlvmState.h"
22#include "MCInstrDescView.h"
23#include "RegisterAliasing.h"
24#include "llvm/ADT/CombinationGenerator.h"
25#include "llvm/MC/MCInst.h"
26#include "llvm/Support/Error.h"
27#include <cstdlib>
28#include <memory>
29#include <vector>
30
31namespace llvm {
32namespace exegesis {
33
34std::vector<CodeTemplate> getSingleton(CodeTemplate &&CT);
35
36// Generates code templates that has a self-dependency.
37Expected<std::vector<CodeTemplate>>
38generateSelfAliasingCodeTemplates(InstructionTemplate Variant,
39 const BitVector &ForbiddenRegisters);
40
41// Generates code templates without assignment constraints.
42Expected<std::vector<CodeTemplate>>
43generateUnconstrainedCodeTemplates(const InstructionTemplate &Variant,
44 StringRef Msg);
45
46// A class representing failures that happened during Benchmark, they are used
47// to report informations to the user.
48class SnippetGeneratorFailure : public StringError {
49public:
50 SnippetGeneratorFailure(const Twine &S);
51};
52
53// Common code for all benchmark modes.
54class SnippetGenerator {
55public:
56 struct Options {
57 unsigned MaxConfigsPerOpcode = 1;
58 };
59
60 explicit SnippetGenerator(const LLVMState &State, const Options &Opts);
61
62 virtual ~SnippetGenerator();
63
64 // Calls generateCodeTemplate and expands it into one or more BenchmarkCode.
65 Error generateConfigurations(const InstructionTemplate &Variant,
66 std::vector<BenchmarkCode> &Benchmarks,
67 const BitVector &ExtraForbiddenRegs) const;
68
69 // Given a snippet, computes which registers the setup code needs to define.
70 std::vector<RegisterValue> computeRegisterInitialValues(
71 const std::vector<InstructionTemplate> &Snippet) const;
72
73protected:
74 const LLVMState &State;
75 const Options Opts;
76
77private:
78 // API to be implemented by subclasses.
79 virtual Expected<std::vector<CodeTemplate>>
80 generateCodeTemplates(InstructionTemplate Variant,
81 const BitVector &ForbiddenRegisters) const = 0;
82};
83
84// A global Random Number Generator to randomize configurations.
85// FIXME: Move random number generation into an object and make it seedable for
86// unit tests.
87std::mt19937 &randomGenerator();
88
89// Picks a random unsigned integer from 0 to Max (inclusive).
90size_t randomIndex(size_t Max);
91
92// Picks a random bit among the bits set in Vector and returns its index.
93// Precondition: Vector must have at least one bit set.
94size_t randomBit(const BitVector &Vector);
95
96// Picks a first bit that is common to these two vectors.
97std::optional<int> getFirstCommonBit(const BitVector &A, const BitVector &B);
98
99// Picks a random configuration, then selects a random def and a random use from
100// it and finally set the selected values in the provided InstructionInstances.
101void setRandomAliasing(const AliasingConfigurations &AliasingConfigurations,
102 InstructionTemplate &DefIB, InstructionTemplate &UseIB);
103
104// Assigns a Random Value to all Variables in IT that are still Invalid.
105// Do not use any of the registers in `ForbiddenRegs`.
106Error randomizeUnsetVariables(const LLVMState &State,
107 const BitVector &ForbiddenRegs,
108 InstructionTemplate &IT);
109
110// Sanity check generated instruction.
111Error validateGeneratedInstruction(const LLVMState &State, const MCInst &Inst);
112
113} // namespace exegesis
114} // namespace llvm
115
116#endif // LLVM_TOOLS_LLVM_EXEGESIS_SNIPPETGENERATOR_H
117