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Re: [PATCH, i386]: Insert "cld" via optimize mode switching

From: Paolo Bonzini <paolo dot bonzini at lu dot unisi dot ch>
To: Uros Bizjak <ubizjak at gmail dot com>
Cc: Michael Matz <matz at suse dot de>, Richard Guenther <richard dot guenther at gmail dot com>, GCC Patches <gcc-patches at gcc dot gnu dot org>
Date: Mon, 04 Dec 2006 15:58:22 +0100
Subject: Re: [PATCH, i386]: Insert "cld" via optimize mode switching
References: <45709025.7090804@gmail.com> <84fc9c000612011343yfd94969x4406a6dbd1a837d9@mail.gmail.com> <45742858.20702@lu.unisi.ch> <Pine.LNX.4.64.0612041515260.29962@wotan.suse.de> <5787cf470612040653u6018aef4qc20fd69f43cb3ad2@mail.gmail.com>

The we in fact need cld insn only after asm statements. MODE_ENTRY can
be set to CLD_FLAG_SET (actually CLD_FLAG_CLEARED...) and call insns
wouldn't set MODE_UNINITIALIZED anymore. If we specify MODE_EXIT as
CLD_FLAG_CLEARED, then optimize_mode_switching pass will automatically
emmit cld after every asm statement, fulfilling ABI requirement about
exit mode.

Is this thinking pushing cld optimization too far?

Given Michael's clarification, I think it absolutely is not.

Paolo

References:
- [PATCH, i386]: Insert "cld" via optimize mode switching
  - From: Uros Bizjak
- Re: [PATCH, i386]: Insert "cld" via optimize mode switching
  - From: Richard Guenther
- Re: [PATCH, i386]: Insert "cld" via optimize mode switching
  - From: Paolo Bonzini
- Re: [PATCH, i386]: Insert "cld" via optimize mode switching
  - From: Michael Matz
- Re: [PATCH, i386]: Insert "cld" via optimize mode switching
  - From: Uros Bizjak

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