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Re: inline asm and multi-alternative constraints

From: Jeff Law <law at redhat dot com>
To: David Wohlferd <dw at LimeGreenSocks dot com>, Segher Boessenkool <segher at kernel dot crashing dot org>
Cc: Sandra Loosemore <sandra at codesourcery dot com>, "gcc at gcc dot gnu dot org" <gcc at gcc dot gnu dot org>, Richard dot Earnshaw at foss dot arm dot com
Date: Mon, 16 Nov 2015 14:45:17 -0700
Subject: Re: inline asm and multi-alternative constraints
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References: <562DA0E2 dot 1040405 at LimeGreenSocks dot com> <562FE71E dot 7010309 at redhat dot com> <563285D8 dot 6020001 at redhat dot com> <563430F8 dot 7020406 at LimeGreenSocks dot com> <5637EC6F dot 7020505 at redhat dot com> <5637F50A dot 1090002 at codesourcery dot com> <56385495 dot 1050507 at LimeGreenSocks dot com> <563D29D7 dot 9000707 at redhat dot com> <20151107004639 dot GA27264 at gate dot crashing dot org> <563DAD50 dot 1010701 at LimeGreenSocks dot com> <56411599 dot 1040507 at redhat dot com> <5643080D dot 3030403 at LimeGreenSocks dot com>

On 11/11/2015 02:19 AM, David Wohlferd wrote:

On 11/9/2015 1:52 PM, Jeff Law wrote:

On 11/07/2015 12:50 AM, David Wohlferd wrote:


- Starting with 'modifiers', "=+&" and (reluctantly) "%" seem reasonable
for inline asm.  But both "#*" seem sketchy.

Right.  =+& are no-brainer yes, as are the constants 0-9.  % is
probably OK as well.

#* are similar to !? in that they are inherently tied into the
register class preferencing implementation and documenting them would
be inadvisable.


Actually, #* are already doc'ed in the user guide.  Are you advising
they be removed?

Yes. Much like ?! they are pretty tied to implementation details, justnot so badly :-)

It may seem like they've got clearer semantics, and they did at onetime, but they don't anymore.


If so, the attached patch does this.  It also removes references to
define_peephole2 and define_splits from the user guide version of this
page.  There are other parts of this page that are more md than ug, but
these are the ones that annoyed me the most.

I'll install momentarily.

jeff

References:
- Re: inline asm and multi-alternative constraints
  - From: Jeff Law
- Re: inline asm and multi-alternative constraints
  - From: Sandra Loosemore
- Re: inline asm and multi-alternative constraints
  - From: David Wohlferd
- Re: inline asm and multi-alternative constraints
  - From: Jeff Law
- Re: inline asm and multi-alternative constraints
  - From: Segher Boessenkool
- Re: inline asm and multi-alternative constraints
  - From: David Wohlferd
- Re: inline asm and multi-alternative constraints
  - From: Jeff Law
- Re: inline asm and multi-alternative constraints
  - From: David Wohlferd

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