Multilib support in Chipyard toolchains?

[baltaz...@gmail.com]

This has been somewhat discussed in other threads, but I seem to be running into a slightly different issue.

I'm trying to compile a test in the chipyard `tests` directory for 32 bit. I added `-march=rv32ima -mabi=ilp32` to the Makefile CFLAGS. This seems to compile okay, but then I hit a bunch of linking errors along the lines of

> riscv-tools-install/lib/gcc/riscv64-unknown-elf/9.2.0/crtend.o: ABI is incompatible with that of the selected emulation:
>  target emulation `elf64-littleriscv' does not match `elf32-littleriscv'

and

> riscv64-unknown-elf/lib/crt0.o: file class ELFCLASS64 incompatible with ELFCLASS32

I tried adding `--enable-multilib` to both libgloss and gcc in the toolchain install script, but it doesn't help. When I use a non-chipyard compiled riscv32 gcc, I get issues in the libgloss makefile ("configure: error: The target architecture of the C compiler does not appear to be RISC-V." even though this is definitely a riscv32 GCC).

Is there a clean way to compile for 32 bit in a way that incorporates the htif linker script?

[Albert Ou]

rv32ima-ilp32 is not one of the default multilib combinations enabled in
riscv-gnu-toolchain. You will need to modify and regenerate configure.ac
yourself:

https://github.com/riscv/riscv-gnu-toolchain/blob/256a4108922f76403a63d6567501c479971d5575/configure.ac#L106

The libgloss configure test is quite definitive, as it checks that the
__riscv built-in macro is defined. If running configure manually, you
must pass the correct --host triplet (as the error message helpfully
suggests), or autoconf instead detects the native gcc.

> Is there a clean way to compile for 32 bit in a way that incorporates the
> htif linker script?
>

It is usually simpler to dispense with multilib and build an ELF
toolchain for the exact march/mabi combination desired by using the
--with-arch and --with-abi configure options. Then libgloss can be
built and used as usual (after providing --host), since gcc will just
use the default target in the absence of -march or -mabi.

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--
Albert Ou

[baltaz...@gmail.com]

Thanks! I realized I actually only needed rv32im-ilp32, which is supported. Thanks for pointing out where to check that!