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Re: GAS .fpu directive
- From: Nicholas Clifton <nickc at redhat dot com>
- To: Renato Golin <renato dot golin at linaro dot org>, binutils at sourceware dot org
- Date: Wed, 20 Aug 2014 16:44:33 +0100
- Subject: Re: GAS .fpu directive
- Authentication-results: sourceware.org; auth=none
- References: <CAMSE1keWd0+uUS0fpaC3-yXsnN-z2_Bsa5anwvQAQwXgWuw_Yw at mail dot gmail dot com>
It seems GAS accepts .fpu anywhere in the file, and the meaning is
that it can change the FPU type mid-way through an assembly file, or
even in a block.
Is that intentional?
Is there any real usage for this kind of thing?
I naively assumed that .cpu / .fpu were like .eabi_attribute flags
that would tell what the *file* is, because normally one assembly
won't run on different machines at the same time.
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. The real reason why
the directive is accepted anywhere is that it was just too much bother
to write additional code to make sure that it is only used once, and
then only in an appropriate place. Much easier to just let it be
accepted anywhere and to rely upon the assembler programmer or the
compiler to only generate one instance of the directive.