https://github.com/ucb-bar/esp-llvm

UCB-BAR fork of LLVM! NOT UPSTREAM RISCV LLVM
https://github.com/ucb-bar/esp-llvm

Last synced: 2 months ago
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UCB-BAR fork of LLVM! NOT UPSTREAM RISCV LLVM

• Host: GitHub
• URL: https://github.com/ucb-bar/esp-llvm
• Owner: ucb-bar
• License: other
• Created: 2013-07-26T20:49:47.000Z (almost 12 years ago)
• Default Branch: riscv-trunk
• Last Pushed: 2021-02-10T12:35:54.000Z (over 4 years ago)
• Last Synced: 2024-05-22T04:54:00.491Z (about 1 year ago)
• Language: C++
• Homepage:
• Size: 506 MB
• Stars: 124
• Watchers: 55
• Forks: 55
• Open Issues: 22
• Metadata Files:
  • Readme: README.md
  • License: LICENSE.TXT

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README

        
Low Level Virtual Machine (LLVM)

======================================================

This directory and its subdirectories contain source code for the Low Level

Virtual Machine, a toolkit for the construction of highly optimized compilers,

optimizers, and runtime environments.

LLVM is open source software. You may freely distribute it under the terms of

the license agreement found in `LICENSE.txt`.

Please see the documentation provided in `docs/` for further

assistance with LLVM, and in particular `docs/GettingStarted.rst` for getting

started with LLVM and `docs/README.txt` for an overview of LLVM's

documentation setup.

If you're writing a package for LLVM, see `docs/Packaging.rst` for our

suggestions.

RISC-V LLVM Support [![Build Status](https://travis-ci.org/riscv/riscv-llvm.svg?branch=riscv-trunk)](https://travis-ci.org/riscv/riscv-llvm)

--------------------------------------------------------

Author  : Colin Schmidt ([email protected])  

Date    : February 24, 2014  

Version : (under version control)  

This repository contains a new target for LLVM RISC-V. It supports the latest

version of the ISA 2.0. This backend currently only supports assembly generation

and riscv64-unknown-\*-gcc must be used to assemble and link the executable. The

[RISCV](https://github.com/riscv/riscv-llvm/tree/RISCV) branch is based on LLVM 3.3 and, the 

[riscv-trunk](https://github.com/riscv/riscv-llvm/tree/riscv-trunk) branch is following upstream LLVM master.

The backend is structured similarly to most other LLVM backends and tries to use 

the tablegen format as much as possible. The description of the instructions

are found in `RISCVInstFormats.td`, and `RISCVInstrInfo*.td`. The registers are 

described in `RISCVRegisterInfo.td` and the calling convention is described in

`RISCVCallingConv.td`.

The instructions are defined using the LLVM IR DAG format, and simple 

instructions that use pre-existing LLVM IR operations should be very easy to

add. The instructions are divided into separate files based on their extension,

e.g. atomic operations are defined in `RISCVInstInfoA.td`. Instructions 

implemented with these patterns are simply matched against the programs LLVM IR

DAG for selection. More complicated instructions can use C++ to perform custom

lowering of the LLVM IR in `RISCVISelLowering.cpp`. Combining of multiple LLVM IR

nodes into single target instructions is also possible using C++ in

the same file. In general `RISCVISelLowering.cpp` sets up the lowering based on

the ISA and the specific subtargets features. 

This backend does not include all features of a backend but is focused on 

generating assembly in an extensible way such that adding new ISA extensions

and using them should be relatively painless. As the RISC-V support develops

the backend may provide more features.

The compiler is fairly robust with similar performance to riscv64-unknown-\*-gcc, so it use

in any and all projects is encouraged.

Feedback and suggestions are welcome.

Installation

------------------------------------------------------------------

The LLVM RISCV backend is built just as the normal LLVM system.

	$ git clone -b RISCV https://github.com/riscv/riscv-llvm.git

	$ git submodule update --init

	$ mkdir build

	$ cd build

  $ cmake -DCMAKE_INSTALL_PREFIX=/opt/riscv -DLLVM_TARGETS_TO_BUILD="RISCV" ../

  $ make

  $ make install

Now if `/opt/riscv` is on your path you should be able to use clang and LLVM with

RISC-V support.

Use

--------------------------------------------------------------------

Using the llvm-riscv is fairly simple to build a full executable however you

need riscv64-unknown-\*-gcc to do the assembling and linking. An example of compiling hello

world:

	$ cat hello.c

	#include 

	int main() {

	    printf("Hello World!\n");

	}

	$ clang -target riscv64 -mriscv=RV64IAMFD -S hello.c -o hello.S

	$ riscv64-unknown-elf-gcc -o hello.riscv hello.S