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PULP RISC-V GNU Compiler Toolchain

This is the PULP RISC-V C and C++ cross-compiler a generic ELF/Newlib toolchain.

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Getting the sources

This repository uses submodules. You need the --recursive option to fetch the submodules automatically

$ git clone --recursive https://github.com/pulp-platform/riscv-gnu-toolchain.git

Alternatively :

$ git clone https://github.com/pulp-platform/riscv-gnu-toolchain.git
$ cd riscv-gnu-toolchain
$ git submodule update --init --recursive

Prerequisites

Several standard packages are needed to build the toolchain. On Ubuntu, executing the following command should suffice:

$ sudo apt-get install autoconf automake autotools-dev curl python3 libmpc-dev libmpfr-dev libgmp-dev gawk build-essential bison flex texinfo gperf libtool patchutils bc zlib1g-dev libexpat-dev

On Fedora/CentOS/RHEL OS, executing the following command should suffice:

$ sudo yum install autoconf automake python3 libmpc-devel mpfr-devel gmp-devel gawk  bison flex texinfo patchutils gcc gcc-c++ zlib-devel expat-devel

On OS X, you can use Homebrew to install the dependencies:

$ brew install python3 gawk gnu-sed gmp mpfr libmpc isl zlib expat

To build the glibc (Linux) on OS X, you will need to build within a case-sensitive file system. The simplest approach is to create and mount a new disk image with a case sensitive format. Make sure that the mount point does not contain spaces. This is not necessary to build newlib or gcc itself on OS X.

This process will start by downloading about 200 MiB of upstream sources, then will patch, build, and install the toolchain. If a local cache of the upstream sources exists in $(DISTDIR), it will be used; the default location is /var/cache/distfiles. Your computer will need about 8 GiB of disk space to complete the process.

Installation (Newlib)

To build the Newlib cross-compiler, pick an install path. If you choose, say, /opt/riscv, then add /opt/riscv/bin to your PATH now. Then, simply run the following command:

./configure --prefix=/opt/riscv --with-arch=rv32imfcxpulpv3 --with-abi=ilp32 --enable-multilib
make

You should now be able to use riscv32-unknown-elf-gcc and its cousins. You can omit --enable-multilib if you are only interested in the specific -march/-mabi combination.

Supported ABIs are ilp32 (32-bit soft-float), ilp32d (32-bit hard-float), ilp32f (32-bit with single-precision in registers and double in memory, niche use only), and ilp32e (embedded abi, fewer caller-saved registers for better interrupt latency)

Troubleshooting Build Problems

Builds work best if installing into an empty directory. If you build a hard-float toolchain and then try to build a soft-float toolchain with the same --prefix directory, then the build scripts may get confused and exit with a linker error complaining that hard float code can't be linked with soft float code. Removing the existing toolchain first, or using a different prefix for the second build, avoids the problem. It is OK to build one newlib and one linux toolchain with the same prefix. But you should avoid building two newlib or two linux toolchains with the same prefix.

Centos (and RHEL) provide old GNU tools versions that may be too old to build a RISC-V toolchain. There is an alternate toolset provided that includes current versions of the GNU tools. This is the devtoolset provided as part of the Software Collection service. For more info, see the devtoolset-7 URL. There are various versions of the devtoolset that are available, so you can also try other versions of it, but we have at least one report that devtoolset-7 works.

Advanced Options

There are a number of additional options that may be passed to configure. See './configure --help' for more details.

Running the Test Suite

The DejaGnu test suite has been ported to RISC-V. This can run with GDB simulator or QEMU. To test GCC, run the following commands:

./configure --prefix=$RISCV --with-arch=rv32ima
make report-gcc-newlib # or make report-gcc-newlib-qemu
make report-binutils-newlib
make report-gdb-newlib

Supported PULP Extensions

Read pulp.md for information about the supported PULP extensions. Read core-v.rst to see how these extension can be used with the cv32e40p.

Check riscv32-unknown-elf-gcc --target=help for supported options in the compiler, riscv32-unknown-elf-gcc-as --help for supported options in the assembler.

In the riscv-isa-manual you can check out how to write ISA strings that specify the enabled extensions. In general, custom extension are denoted by a leading x followed the extension name. Extension are separated by and underscore _ and you can also specify version numbers by appending a string xpy e.g. 2p0 do specify version 2.0. Here a few quick commands:

• riscv32-unknown-elf-gcc -march=rv32imfcxpulpv3 FILES: rv32 with the imfc standard extension and the pulpv3 extension group.

• riscv32-unknown-elf-gcc -march=rv32imc_xpulphwloops_xpulppostmod FILES: rv32 with imc standard extension, pulp hardware loop and pulp load-store post modify instructions.

Sometimes you want to run with an extension group such as xpulpv3 but disable certain subsets e.g. hardware loops. Do it like this:

• riscv32-unknown-elf-gcc -march=rv32imfc_xpulpv3 -mno-pulp-hwloop FILES

Check riscv32-unknown-elf-gcc --target=help for more such switches.