Re: [PATCH v2 21/30] Deprecate 32 bit big-endian MIPS

[Pierre Muller <pierre@freepascal.org>]

Le 16/09/2022 à 10:38, Richard Henderson a écrit :
> On 9/16/22 10:08, Pierre Muller wrote:
>>
>>     I am using gcc230 machine for the gcc compile farm.
>>
>>     This is a big endian mips64 machine runnig Debian Buster.
>>
>> When compiling the qemu 7.1.0 release source,
>> the generated binaries are 32-bit mips binaries,
>> and I did not find out how to generate a 64-bit versions
>> of the executables.
> 
> Yes, that host seems to have been installed with the o32 abi instead of the n64 (or n32) abi.

Indeed,
>>     As mips32 seems to still be the default arch that gcc uses,
>> I don't really understand the idea of depreciating big endian mips32.
>>
>> Is this solely related to cross-compilation issues?
> 
> Yes.  Even gcc230 is fairly small for actually compiling qemu, it takes many hours.  So
> for many hosts we rely on cross-compilation from x86_64.
> 
> For that, we rely on the set of cross-compilers built by Debian 11 (bullseye) plus (!) the
> host libraries for that platform.  We cannot simply rely on crossbuild-essential-mips
> because building qemu requires many more system libraries than just libc.
> 
> In https://www.debian.org/releases/bullseye/, you'll note that big-endian mips is not
> listed, so we are now missing those system libraries.

  So this is not limited to mips32, as big endian mips64 is also not supported anymore in bulleye...

> We are not intending to *remove* support for big-endian mips, as 99% of the code paths are
> shared with little-endian mips, which we can continue to test.  But we are now saying that
> big-endian mips is not "supported" and might break.

   Thank you for your answer and the clarifications!

Pierre