This is the mail archive of the gcc@gcc.gnu.org mailing list for the GCC project.

Index Nav:	[Date Index] [Subject Index] [Author Index] [Thread Index]
Message Nav:	[Date Prev] [Date Next]	[Thread Prev] [Thread Next]
Other format:	[Raw text]

Re: virtual stack regs.

From: "Uros Bizjak" <ubizjak at gmail dot com>
To: "Rask Ingemann Lambertsen" <rask at sygehus dot dk>
Cc: "Kenneth Zadeck" <zadeck at naturalbridge dot com>, gcc at gcc dot gnu dot org
Date: Tue, 19 Jun 2007 11:11:54 +0200
Subject: Re: virtual stack regs.
References: <46772329.5010500@naturalbridge.com> <20070619090455.GH5690@sygehus.dk>

On 6/19/07, Rask Ingemann Lambertsen <rask@sygehus.dk> wrote:

> 3) If they really are uninitialized, why is it a problem to assign zero
> to them.

   It is possible to mess up the substitution that the vregs pass performs.
IIRC, it happened to me once because I accidentally put one of these virtual
pseudo inside a (clobber) or (use) or something like that. I don't quite
recall the details, but maybe the substitution fails if they appear outside
an operand?


There is one annoying case in PR32374, where on-the-stack constructor
creates invalid memory clobber that includes virtual-stack-regs. These
are simply ignored by vregs pass and this confuses dataflow register
initialization.

Uros.

Follow-Ups:
- Re: virtual stack regs.
  - From: Rask Ingemann Lambertsen

References:
- virtual stack regs.
  - From: Kenneth Zadeck
- Re: virtual stack regs.
  - From: Rask Ingemann Lambertsen

Index Nav:	[Date Index] [Subject Index] [Author Index] [Thread Index]
Message Nav:	[Date Prev] [Date Next]	[Thread Prev] [Thread Next]