https://gcc.gnu.org/bugzilla/show_bug.cgi?id=110899
Maxim Egorushkin <maxim.yegorushkin at gmail dot com> changed:
What |Removed |Added
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CC| |maxim.yegorushkin at gmail dot
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--- Comment #14 from Maxim Egorushkin <maxim.yegorushkin at gmail dot com> ---
(In reply to Marco Elver from comment #0)
> On X86-64 the callee preserves all general purpose registers, except for
> R11. R11 can be used as a scratch register.
R11 is reserved for use in those lazy-resolved PLT stubs, invented for
OpenOffice to load faster than users giving up waiting on it and buying MS
Office instead.
In other words, R11 is assumed to be wiped by any/every call instruction on its
own, since any call instruction may need to resolve a PLT stub on its way.
You may like to compile your code with `-fno-plt` to bypass calling those pesky
PLT stubs invented for OpenOffice. But that doesn't affect the machine code of
any 3rd-party libraries you invoke, they still do their calls through PLT and,
hence, may clobber R11.
R10 is also clobbered by some nebulous features no user asked for, and, hence,
is generally unavailable, except in tail functions making no calls.
