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From: anton@mips.complang.tuwien.ac.at (Anton Ertl)
Newsgroups: comp.arch
Subject: Re: Calling conventions (particularly 32-bit ARM)
Date: Tue, 14 Jan 2025 18:02:29 GMT
Organization: Institut fuer Computersprachen, Technische Universitaet Wien
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Michael S <already5chosen@yahoo.com> writes:
>On Tue, 14 Jan 2025 14:22:19 GMT
>scott@slp53.sl.home (Scott Lurndal) wrote:
>> Clearly there are programmers who wish to be able to detect
>> certain exceptions, and POSIX allows programmers to
>> select that behavior.
>
>Raising of FP exceptions is orthogonal to question of one instruction
>vs library call. If anything, when exceptions are enabled, with
>single-instruction implementation it is probably easier for exception
>handler to find the reason and generate useful diagnostics.

It seems to me that "raise an exception" is in the IEEE 754 sense (by
default set a sticky flag in an internal register), not in the C sense
of raising a signal.  AFAIK you can tell the system to produce a
signal for some exceptions, but the default on Linux is not to.

>As to what POSIX allows, on the manual page that you quoted I see no
>indication that implementation is required to give to programmer to
>select this or that behavior. I read it like implementation is allowed
>to make the choice fully by itself.

And if it is friendly, it can give the programmer a compiler option to
select between the variants.

- anton
-- 
'Anyone trying for "industrial quality" ISA should avoid undefined behavior.'
  Mitch Alsup, <c17fcd89-f024-40e7-a594-88a85ac10d20o@googlegroups.com>