如何仅为RV32I基本整数指令和扩展M编译C代码？

Question

I have started to work with risc-v few days ago, but yesterday I had a problem. The problem is the following:

I want to compile code for example for the RV32I base integer instruction set and I want to add too the "M" Standard Extension.

When I compile the C code I use the following command

riscv64-unknown-elf-gcc Program.c -o Program.o -m32 -march=RV32IM

Now if for example I want to see assembler code, I use

riscv64-unknown-elf-objdump -d Program.c > Program.dump

Now, if I explore the dump file "Program.dump" . I have noticed that sometimes appear assembly instructions as:

   10c6c:   00a12427            fsw fa0,8(sp)
   10dd0:   00a42023            sd a0,8(sp)

among many other cases.

If I see the "RISC-V Instruction Set Manual, Volume I: User-Level ISA, Version 2.0" at page 52 I observe that the fsw instruction belongs a RV32F Standard Extension and the sd instruction , it belongs to RV64I.

For this reason, I am confused I don't know if my problem is that I am not compiling well.

My question is: How can I compile C code only for the RV32I base integer instruction and the extension M?

Answer 1

As Chris pointed out, the problem seems to be that the libraries have not been built for RV32I.

This is a copy&paste from my instructions here for how to build a pure RV32I toolchain+libraries from git rev 5b1febd (2015-07-05) of riscv-gnu-toolchain:

sudo mkdir /opt/riscv32i
sudo chown $USER /opt/riscv32i

git clone https://github.com/riscv/riscv-gnu-toolchain riscv-gnu-toolchain-rv32i
cd riscv-gnu-toolchain-rv32i
git checkout 5b1febd

mkdir build; cd build
../configure --with-xlen=32 --with-arch=I --prefix=/opt/riscv32i
make -j$(nproc)

This will install a RV32I toolchain with the riscv32-unknown-elf- command prefix.

There seems to be a problem with --with-xlen=32 --with-arch=I in current git head of riscv-gnu-toolchain. I've now reported the issue on github.