Scripts for GNU Toolchain for ARC-V Targets

This repository contains two useful scripts for the ARC-V GNU toolchain:

1. The riscv64-snps-elf-tcf-gcc tool is a TCF wrapper for GCC for ARC-V targets. It is intended to be used with TCF files originally prepared for MetaWare tools.
2. The riscv64-snps-elf-buildlib tool allows building Picolibc, libgcc, and libstdc++ for a particular set of target and optimization options. Then this configuration may be used for building applications using the TCF wrapper.

Installation

Copy all the scripts, including arcgnulib.py, to the bin directory of a toolchain or add a directory with the scripts to PATH. Note that both scripts try to locate riscv64-snps-elf-gcc in two places:

1. The same directory where the scripts reside.

   If the scripts' directory contains riscv64-snps-elf-gcc, then this binary is used.

2. A directory in PATH.

Note that the scripts' prefix must match GCC's one. For example, if GCC binary is riscv64-unknown-elf-gcc then scripts must be renamed to riscv64-unknown-elf-tcf-gcc and riscv64-unknown-elf-buildlib.

The TCF wrapper

The TCF Wrapper is a wrapper for GCC from the GNU toolchain for ARC-V that takes target options from a TCF file and passes them to GCC. The wrapper introduces a list of extra options prefixed with -tcf:

• -tcf=<path> - use a TCF file for parsing GCC options.
• -tcf-debug - enable printing of debug messages.
• -tcf-dry-run - do not execute the final command, only print it.
• -tcf-help - show a help message.
• -tcf-no-compressed - remove extensions for compressed instructions from -march string. It removes these extensions: c, zca, zcb, zcf, zcd, zcmp, zcmt. It may be useful for targets with slow compressed instructions.
• -tcf-with-memory-defines - pass memory layout variables from TCF through -defsym for a linker file for Newlib (takes effect only with -T arcv.ld) or Picolibc toolchains (takes effect only with -specs=picolibc.specs/picolibcpp.specs). Values for code and data memory layouts are inferred from configurations of ICCM and DCCM memory regions in a TCF. If a TCF does not contain CMM, then nothing will be passed to GCC.
• -tcf-buildlib=<path> - pass a path to a directory with a buildlib configuration. GCC will use libraries from this directory for linking. You can find details in the next section of this README.

An example of using the wrapper with a TCF:

$ riscv64-snps-elf-tcf-gcc -g -O2 -tcf=rmx100_dmips.tcf -tcf-debug -specs=picolibc.specs --oslib=semihost --crt0=semihost main.c -o main.elf
...
DEBUG: Running GCC:
<...>/riscv64-snps-elf-gcc -g -O2 -march=rv32i_zicsr_zifencei_zihintpause_a_zca_m_zcb_zcmp_zcmt_zba_zbb_zbs_zicond_zicbom_zicbop -mtune=arc-v-rmx-100-series -mabi=ilp32 -mcmodel=medlow -mno-strict-align --param arcv-mpy-option=1c -specs=picolibc.specs --oslib=semihost --crt0=semihost main.c -o main.elf

Pass memory definitions for a linker script:

$ riscv64-snps-elf-tcf-gcc -g -O2 -tcf=rmx100_dmips.tcf -tcf-debug -tcf-with-memory-defines -specs=picolibc.specs --oslib=semihost --crt0=semihost main.c -o main.elf
...
DEBUG: Running GCC:
<...>/riscv64-snps-elf-gcc -g -O2 -march=rv32i_zicsr_zifencei_zihintpause_a_zca_m_zcb_zcmp_zcmt_zba_zbb_zbs_zicond_zicbom_zicbop -mtune=arc-v-rmx-100-series -mabi=ilp32 -mcmodel=medlow -mno-strict-align --param arcv-mpy-option=1c -Wl,-defsym=txtmem_addr=0x0 -Wl,-defsym=__flash=0x0 -Wl,-defsym=txtmem_len=0x8000 -Wl,-defsym=__flash_size=0x8000 -Wl,-defsym=datamem_addr=0x80000000 -Wl,-defsym=__ram=0x80000000 -Wl,-defsym=datamem_len=0x8000 -Wl,-defsym=__ram_size=0x8000 -specs=picolibc.specs --oslib=semihost --crt0=semihost main.c -o main.elf

The Buildlib tool

Overview

The Buildlib tool allows building all toolchain libraries for a particular set of target and optimization options and then building applications using these prebuilt libraries. Buildlib builds libgcc, Picolibc, and libstdc++.

Here is a list of usage examples:

• Build libraries for rhx100_base.tcf TCF template:

  $ riscv64-snps-elf-buildlib --output rhx100_base --tcf rhx100_base.tcf --nproc 4
  INFO: Found GCC in PATH: /SCRATCH/ykolerov/tools/gcc-arcv-elf-picolibc-latest/bin/riscv64-snps-elf-gcc
  INFO: Final target options:
  -march=rv32i_zicsr_zifencei_zihintpause_a_zca_m_zcb_zcmp_zba_zbb_zbs_zicond_zicbom_zicbop -mabi=ilp32 -mtune=arc-v-rhx-100-series -mcmodel=medlow
  INFO: Final cflags:
  -mno-strict-align -g -O2
  INFO: Cloning Picolibc repository.
  INFO: Creating a build directory: /home/ykolerov/workspace/arc-v/gcc-buildlib/custom-build/arcv-tcf-wrapper/rhx100_base/build-picolibc
  INFO: Configuring Picolibc library.
  INFO: Building Picolibc library.
  INFO: Installing Picolibc library.
  INFO: Cloning GCC repository.
  INFO: Downloading GCC dependencies.
  INFO: Creating a build directory: /home/ykolerov/workspace/arc-v/gcc-buildlib/custom-build/arcv-tcf-wrapper/rhx100_base/build-gcc
  INFO: Configuring GCC.
  INFO: Building libgcc and libstdc++.
  INFO: Installing libgcc and libstdc++.
  INFO: Saving buildlib.specs.
  INFO: Finished building and installing libgcc and libstdc++.
  
  $ riscv64-snps-elf-tcf-gcc -tcf=rhx100_base.tcf -tcf-buildlib=./rhx100_base -specs=picolibc.specs --oslib=semihost --crt0=semihost hello.c -o hello.elf
  

• Pass all target options explicitly without using a TCF and then build your application with the prebuilt libraries:

  $ riscv64-snps-elf-buildlib --output buildlib --march rv32imac --mabi ilp32 --mtune arc-v-rmx-100-series --cflags="-g -O3" -j 4
  ...
  $ riscv64-snps-elf-tcf-gcc -march=rv32imac -mabi=ilp32 -mtune=arc-v-rmx-100-series -tcf-buildlib=./buildlib -specs=picolibc.specs --oslib=semihost --crt0=semihost hello.c -o hello.elf
  

Here is a list of all command line options:

• -h, --help - show the help message and exit.
• --output PATH, -bd PATH, -buildlib_dir PATH - set the path to the output directory.
• --tcf TCF, -tcf TCF - set the path to a TCF configuration file.
• --march ARCH, -march ARCH - set the value for the -march target option.
• --mabi ABI, -mabi ABI - set the value for the -mabi target option.
• --mtune TUNE, -mtune TUNE - set the value for the -mtune target option.
• --mcmodel CMODEL, -mcmodel CMODEL - set the value for the -mcmodel target option. By default, -mcmodel=medlow for rv32 and -mcmodel=medany for rv64.
• --cflags CFLAGS - pass extra target flags to GCC (default: -g0 -O2).
• --no-libstdcpp, -nocplus - do not build libstdc++ library.
• --gcc-sources-git-branch PATH - set the release branch for GCC (default: arc-2026.03).
• --gcc-sources-dir-path PATH - set the path to GCC sources (overrides --gcc-sources-git-branch).
• --picolibc-sources-git-branch PATH - set the release branch for Picolibc (default: arc-2026.03).
• --picolibc-sources-dir-path PATH - set the path to Picolibc sources (overrides --picolibc-sources-git-branch).
• --flash-addr ADDR - set the default value for the flash address (default: 0x0).
• --flash-size SIZE - set the default value for the flash size (default: 128K).
• --ram-addr ADDR - set the default value for the RAM address (default: 0x40000000).
• --ram-size SIZE - set the default value for the RAM size (default: 128K).
• --nproc N, -j N - set the number of threads for building (default: 1).
• --no-clean, -noclean - do not delete build artifacts.
• --debug, -v - show debug messages.

Known issues

• The --cflags option works correctly only in the --cflags=".." form.
• The Buildlib tool works only with a Picolibc toolchain for ARC-V.

Technical details

These steps are performed to build a custom configuration:

• First, buildlib tries to find riscv64-snps-elf-gcc in PATH or in a local directory. It fails if GCC cannot be found.
• Create the main buildlib directory and build directories for Picolibc and GCC. Create symbolic links for Picolibc and GCC sources.
• Configure, build, and install Picolibc and then GCC. All libraries are installed to the buildlib directory.
• Delete symbolic links to sources and build directories for Picolibc and GCC (if --no-clean is not passed).

Basically, a buildlib directory is a subset of the toolchain's directory. Here is a buildlib directory structure:

$ tree -d -L 3 buildlib
buildlib
├── lib
│   └── gcc
│       └── riscv64-snps-elf
├── riscv64-snps-elf
│   ├── include
│   │   ├── arpa
│   │   ├── bits
│   │   ├── c++
│   │   ├── machine
│   │   ├── rpc
│   │   ├── ssp
│   │   └── sys
│   ├── lib
│   └── sys-include
│       ├── arpa
│       ├── bits
│       ├── machine
│       ├── rpc
│       ├── ssp
│       └── sys
└── share
    └── gcc-15.2.0
        └── python

To build and link an application with a custom library, you need to pass extra arguments:

• -specs=./buildlib/buildlib.specs - include a .specs file which turns off default multilib rules.
• -isystem ./buildlib/riscv64-snps-elf/sys-include -isystem ./buildlib/riscv64-snps-elf/include - use includes from a custom Picolibc build.
• -B./buildlib/lib/gcc -B./buildlib/riscv64-snps-elf/lib - use custom libraries by default instead of original ones.

Now consider this example:

int main()
{
    printf("Hello, World!\n");
    return 0;
}

How to link an application with custom libraries (also, we pass -Wl,-t to ensure that custom libraries are linked with our application):

$ riscv64-snps-elf-gcc \
     -march=rv32imac \
     -mabi=ilp32 \
     -mtune=arc-v-rmx-100-series \
     -mcmodel=medlow \
     -isystem ./buildlib/riscv64-snps-elf/sys-include \
     -isystem ./buildlib/riscv64-snps-elf/include \
     -B./buildlib/lib/gcc \
     -B./buildlib/riscv64-snps-elf/lib \
     -specs=picolibc.specs \
     -specs=buildlib.specs \
     --oslib=semihost \
     --crt0=semihost \
     hello.c -o hello.elf \
    -Wl,-t
./buildlib/riscv64-snps-elf/lib/crt0-semihost.o
/tmp/ccUptbxg.o
./buildlib/lib/gcc/riscv64-snps-elf/15.2.0/libgcc.a
./buildlib/lib/gcc/riscv64-snps-elf/15.2.0/libgcc.a
./buildlib/riscv64-snps-elf/lib/libc.a
./buildlib/riscv64-snps-elf/lib/libsemihost.a
./buildlib/lib/gcc/riscv64-snps-elf/15.2.0/libgcc.a
./buildlib/riscv64-snps-elf/lib/libc.a
./buildlib/riscv64-snps-elf/lib/libsemihost.a
./buildlib/lib/gcc/riscv64-snps-elf/15.2.0/libgcc.a

Now we can run the example in nSIM:

$ nsimdrv -p nsim_isa_family=rv32 -p nsim_isa_ext=-all.i.m.a.c.zicsr -p nsim_semihosting=1 -p enable_exceptions=0 hello.elf
Hello, World!

Run tests

$ python3 -m pytest -v