1. Introduction

RVEmitter is a playground space for a primitive instruction emitter targetting Risc5 ISA.

2. Dependencies

The following dependencies must be installed on the build instance depending on the build configuration.

2.1 Base framework only (lite build)

meson
fmt
clang
clang-tools

2.2 Verilated model

On top of the lite build requirements include:

verilator
any riscv softcore rtl

2.3 Qemu build

Wip

2.3 Spike Sim build

Wip

3. Compile

To compile the code simply issue the following commands:

chmod +x compile.sh (required first time)
./compile.sh

You may also run sanitize.sh if you'd like to use clang-address-sanitizer.

4. Intended use

To generate code 3 components are required:

A basic block that holds the generated instructions and data.
A register allocator to allocate registers on demand (or fallback to stack if there are no available registers).
An emitter that emits instructions within basic block's memory space.

The example below performing a simple addition demonstrates the intended use of the framework by a JIT/AOT compiler:

const int32_t SimpleTest::Run(const int argc, const char** argv) {
    fmt::print("Simple test start..\n");

    // Create a basic block to emit instructions & Define label and offset.
    constexpr const std::string_view bb_label = "main";
    constexpr const size_t bb_offset = 0;
    std::unique_ptr< BasicBlock >  bb { std::make_unique<BasicBlock>(bb_label, bb_offset) };

    // Create a register allocator
    std::unique_ptr< RegisterAllocatorInterface > ralloc { std::make_unique<RV32E_SimpleRegisterAllocator>() };

    // Create an emitter and pass in the block & reg allocator
    std::unique_ptr< EmitterInterface > emitter { std::make_unique<RV32E_Emitter>( bb.get(), ralloc.get()) };

    // Get 2 available registers to work
    const auto lhs = ralloc->GetNextGPR(rcls_temp);
    const auto rhs = ralloc->GetNextGPR(rcls_temp);
    assert ((lhs != k_invalid_reg_index) && (rhs != k_invalid_reg_index) );

    // Move data
    emitter->LoadImmediate(lhs, 64);
    emitter->LoadImmediate(rhs, 32);

    // Perform lhs(rd) = lhs(rs1) + rhs(rs2) 
    emitter->AddRmRn(lhs, lhs, rhs);

    // Free registers
    ralloc->FreeGPR(lhs);
    ralloc->FreeGPR(rhs);

    // Code is now stored in bb->GetCode()
    fmt::print("Simple test end..\n");

    // Done
    return 0;
}

4. Running tests

Currently all tests run from within the main entry point of the application. No dedicated TestBench or automated testing flow is set.

5. Supported ISAS & Instructions

6. Project structure

wip

DimitrisVlachos/RVEmitter