[Bug 38780] AArch64 platforms: register X18 must remain reserved for Wine to run 64-bit ARM Windows applications (Distro aarch64 toolchains need '-ffixed-x18' default, loader/libc/userland)

[wine-bugs at winehq.org]

https://bugs.winehq.org/show_bug.cgi?id=38780

--- Comment #5 from Anastasius Focht <focht at gmx.net> ---
Hello André,

--- quote ---
It seems to me that the key is to configure gcc with:
--with-specs=%{!ffixed-x18:-ffixed-x18}
Can someone confirm? So that we can guide people how to do it...
--- quote ---

that would be one way.

Ultimately it's the distro gcc package maintainer to decide how to implement it
- not the end users.

For Fedora (the distro I use) the contact would be Jakub Jelinek

https://admin.fedoraproject.org/pkgdb/package/gcc/

Gcc package repository:

http://pkgs.fedoraproject.org/cgit/gcc.git/tree/

The .spec file to add the option for '%ifarch aarch64':

http://pkgs.fedoraproject.org/cgit/gcc.git/tree/gcc.spec

But ... I've had a look at the aarch64 config for gcc and noticed this:

https://github.com/gcc-mirror/gcc/blob/master/gcc/config/aarch64/aarch64.h#L359

--- snip ---
#define STATIC_CHAIN_REGNUM    R18_REGNUM
--- snip ---

Whoops. To avoid multiple files changed/patched for this "feature" (gcc arch
config header and the .spec file which is distro/build system specific anyway)
one could put a small patch together which only affects one file:

gcc/config/aarch64/aarch64.h

'ffixed-x18' can also be realized by modifying FIXED_REGISTERS,
CALL_USED_REGISTERS register allocator bitmaps (1 = exclude from general use)

https://github.com/gcc-mirror/gcc/blob/master/gcc/config/aarch64/aarch64.h#L275

Regards

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