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Date: Fri, 13 Mar 2015 19:59:31 +0200
From: Konstantin Belousov <kostikbel@gmail.com>
To: Nathan Whitehorn <nwhitehorn@freebsd.org>
Subject: Re: svn commit: r279937 - in head/sys/powerpc: include powerpc
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On Fri, Mar 13, 2015 at 10:45:46AM -0700, Nathan Whitehorn wrote:
> We'll need to hack the compiler in this case, since it assumes setjmp() 
> saves and restores the vector registers. I'm really not sure which 
> option is worse.

Changing the compiler is arguably much worse than breaking ABI of the
tier 2 platform, indeed.  We must maintain the situation where the stock
build of the compilers work out of box.

Still, how the compiler' assumptions are laid out ?  It could be argued
that compilers on x86 also assume that FPU register file is restored by
longjmp.  %st* and %xmm* are defined as not preserved across function
calls, but I suspect that practical rule for setjmp() is that floating
vars better not be used in the target frame.

Hm, indeed f14-f31 and v20-v31 are marked as non-volatile for 64bit ABI.