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