loganleland / llvm

Mirror of official llvm git repository located at http://llvm.org/git/llvm. Updated every five minutes.

LLVM

This directory and its subdirectories contain source code for LLVM, a toolkit for the construction of highly optimized compilers, optimizers, and runtime environments. On top of LLVM 3.9, an experimental backend targeting ANSI C is being implemented for the PIC16F877 in lib/Target/PIC16.

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 are writing a package for LLVM, see docs/Packaging.rst for our suggestions.

PIC16F877

A microcontroller created by MicroChip, more details can be found here: http://www.microchip.com/wwwproducts/en/PIC16F877A

Quick Start

This repo can be built from source. To do this, follow the offical LLVM guide to building: http://llvm.org/docs/CMake.html

Alternatively this project's binaries can be downloaded: This executable was built using Debian Jessie, although it should work for any x86 linux operating system.

wget https://github.com/loganleland/llvm/releases/download/rc1/pic16rc1.tar.gz
tar -zxvf pic16rc1.tar.gz
PATH=$PATH:$PWD/PIC16rc1

Usage

If you downloaded the binary:

compilePIC16 source.c

If you built from source:

postLLC can be found at llvm/lib/Target/PIC16/postLLC.sh

clang -S -emit-llvm -target pic16 source.c
llc -mcpu=generic -march=pic16 source.ll
postLLC.sh source.s

Survey

While using this compiler it would be greatly beneficial to the developers of this backend if you fill out the following survey: https://goo.gl/forms/AYxzRiEtKxIy9aBy2

Limitations

This backend is a preliminary prototype undergoing active development. Pull requests are very welcome.

Currently Supported:

• Functions
• Variable scoping
• Control Structures
• Variable assignment
• Integer addition/subtraction
• Bitwise operations: &,|,^
• integer comparisons: &&, ||, ==, !=

Compiler Overview

Languages

• ANSI C: Everyday C
• LLVM IR: LLVM's intermediate representation
• PIC16 ISA: PIC16F877's ISA

Compiler Phases

ANSI C

• ANSI C to LLVM IR clang

LLVM IR

• LLVM IR to Pre-PIC16 ISA llc

Pre-PIC16 ISA

• Pre-PIC16 ISA to PIC16 ISA postLLC: Transforms the llc output assembly into PIC16 ISA (will be removed once assembler is implemented)

PIC16 ISA

• PIC16 ISA to Byte-code mpasm

Future Work

• Implement assembler
• Implement multiplication and division
• Implement more integer comparisons
• Refactor
• Create API for timing, I/O ports, etc
• Currently our implementation is confined to one out of the four available banks of general purpose registers. Using more of these banks would allow for more variables
• Implement vector support