GCB tool chain instructions

Nanhu structure of Xiangshan support RV64GCBK extension (RV64IMAFDC_zba_zbb_zbc_zbs_zbkb_zbkc_zbkx_zknd_zkne_zknh_zksed_zksh_svinval)

This instruction explains how to compile B extension GNU tool as GNU toolchain release does not support it yet. You can modify the configuration options in this instruction if you need more support such as K extension.

Release notes of tool chain

~~Option 1 (Deprecated)~~

• riscv-gnu-toolchain official master branch (df6ecbe4ddb2a1a261b44af822d22f1253d3f0e4 verified)
• Replace riscv-gcc with the version of ISCAS https://github.com/pz9115/riscv-gcc switch to branch riscv-gcc-experimental-bkp (fbfa8d9ad496a2d69a38be2c2c3c0dc0956ffb9e verified)
• Replace riscv-binutils with the version of ISCAS https://github.com/pz9115/riscv-binutils-gdb switch to branch riscv-binutils-experimental-bkp (586f9af7f39d5185e8c133ab794167e46bd721de verified)

(Hint: you can clone riscv-gnu-toolchain before replacing riscv-gcc and riscv-binutils as above)

~~Option 2 (Deprecated)~~

To simplify the operation of switching branchs in submodule, Xiangshan forked a riscv-gnu-toolchain and had updated the submodules in order to support B extension and K extension. Submodules in this repository has been switched and can be compiled directly without switching manually.

git clone git@github.com:OpenXiangShan/riscv-gnu-toolchain.git

Option 3 (Recommended)

For users in China, we highly recommend using the mirrors provided by PLCT at ISCAS. We express our special thanks to them for providing the mirrors for riscv-gnu-toolchain and had updated the submodules constantly.

## to clone (not recommended)
git clone https://mirror.iscas.ac.cn/riscv-toolchains/git/riscv-collab/riscv-gnu-toolchain.git
## to clone with submodules (recommended)
curl https://mirror.iscas.ac.cn/riscv-toolchains/git/riscv-collab/riscv-gnu-toolchain.sh | bash

For users outside China, we recommend using the official riscv-gnu-toolchain repository.

Compiling method of tool chain

Install related standard packages

Please refer to the corresponding parts in riscv-gnu-toolchain official documents。

Compile tool chain

cd riscv-gnu-toolchain
mkdir build
cd build
../configure --prefix=PATH_TO_INSTALL --with-arch=rv64gc_zba_zbb_zbc_zbs
# newlib (riscv-unknown-elf-)
make -jN
# linux (riscv-unknown-linux-gnu-)
make linux -jN

• If make fails, it may be a permissions issue, so try again with the sudo make command
• Set the environment variable RISCV=PATH_TO_INSTALL after compiling
• Add RISCV/bin to PATH

export RISCV=PATH_TO_INSTALL
export PATH=$RISCV/bin:$PATH

Generate B extension instructions

Add -march=rv64gc_zba_zbb_zbc_zbs to gcc compilation options

Here we take an example of compilation applications in AM:

# $AM_HOME/am/arch/isa/riscv64.mk

-COMMON_FLAGS  := -fno-pic -march=rv64gc -mcmodel=medany
+COMMON_FLAGS  := -fno-pic -march=rv64gc_zba_zbb_zbc_zbs -mcmodel=medany