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Re: GAS .fpu directive
- From: Peter Bergner <bergner at vnet dot ibm dot com>
- To: Nicholas Clifton <nickc at redhat dot com>
- Cc: Renato Golin <renato dot golin at linaro dot org>, binutils at sourceware dot org
- Date: Wed, 20 Aug 2014 11:17:23 -0500
- Subject: Re: GAS .fpu directive
- Authentication-results: sourceware.org; auth=none
- References: <CAMSE1keWd0+uUS0fpaC3-yXsnN-z2_Bsa5anwvQAQwXgWuw_Yw at mail dot gmail dot com> <53F4C261 dot 8090900 at redhat dot com>
On Wed, 2014-08-20 at 16:44 +0100, Nicholas Clifton wrote:
> Renato Golin wrote:
> > The only use case I can think of is if there is a conditional jump
> > based on the existence of instructions, so a block that has neon is
> > only executed if there's no exception, but that still doesn't need a
> > .fpu vfp somewhere else.
>
> Right. Basically such an sceanario is theoretically possible, but it is
> unlikely that it will ever turn up in real code.
Is this true for .machine as well? If so, I know we emit a .machine <cpu>
midway through some glibc code to temporarily modify the .machine value
in as assembler file, before changing it back. The ugly details are here:
https://sourceware.org/ml/binutils/2009-01/msg00278.html
As Alan mentions in the follow-up, we ended up using:
.machine push
.machine power6
source that needs power6 insn
.machine pop
...so there is _some_ use for being able to emit these directives anywhere
in the source file.
Peter