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From: Tom Tromey <tromey@redhat.com>
To: Pedro Alves <pedro@codesourcery.com>
Cc: gdb-patches@sourceware.org, Daniel Jacobowitz <drow@false.org>
Subject: Re: RFC: partially available registers
References: <m3vcv6xegp.fsf@fleche.redhat.com>	<201107221425.46930.pedro@codesourcery.com>	<m3ei1iz6k5.fsf@fleche.redhat.com>	<201107221940.32070.pedro@codesourcery.com>
Date: Fri, 22 Jul 2011 19:19:00 -0000
In-Reply-To: <201107221940.32070.pedro@codesourcery.com> (Pedro Alves's	message of "Fri, 22 Jul 2011 19:40:31 +0100")
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>>>>> "Pedro" == Pedro Alves <pedro@codesourcery.com> writes:

Pedro> Ah, that's it then.  I was curious to know why were the
Pedro> upper parts of the ymm unavailable.

amd64_linux_fetch_inferior_registers calls ptrace(PTRACE_GETREGSET)
to fetch the registers.  Then it passes this to amd64_supply_xsave,
which calls i387_supply_xsave.  This function then decodes the "XCR0"
flag and determines that the upper parts were not supplied by the
kernel; that is, we take the true branch here:

	  if ((clear_bv & I386_XSTATE_AVX))
	    p = NULL;
	  else
	    p = regs;

Tom