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Re: Effect of 'register' keyword on debug info

From: Ian Lance Taylor <iant at google dot com>
To: Rohit Arul Raj <rohitarulraj at gmail dot com>
Cc: gcc-help at gcc dot gnu dot org
Date: Fri, 25 May 2012 06:11:38 -0700
Subject: Re: Effect of 'register' keyword on debug info
References: <CAPVMLfWHqD2caZroPUWPPOcgOOThBw0+YksZ1F9SXS2hbH64XQ@mail.gmail.com> <mcrlikituoi.fsf@dhcp-172-18-216-180.mtv.corp.google.com> <CAPVMLfWKfnmBWbSBGuSEtMh8ScEVyX8Zm0GXqH5-85o+zwvK-w@mail.gmail.com> <mcrtxz5r5ow.fsf@dhcp-172-18-216-180.mtv.corp.google.com> <CAPVMLfUpZUxSW2g5tTjSdAPiB=ADiiKWebUEAZHDur408VYMjQ@mail.gmail.com>

Rohit Arul Raj <rohitarulraj@gmail.com> writes:

> Further, by default the debug info for variables 'd1' and 'f1' are
> generated as location expressions. Where as with '-fvar-tracking', the
> debug info is generated as location lists.
>
> 1) Is it possible to generate location expressions to identify that
> the variable has been optimized out?

I don't know.

> 2) If (1) is not possible and if '-fvar-tracking' gives accurate info
> on live variables, why isn't it turned ON by default at '-O0'?

That is a good question.  Right now -fvar-tracking is turned on by
default at -O1.  I guess the assumption was that at -O0 variables
wouldn't wind up in the same register.

> Since the code is compiled at '-O0' should correct debug info be generated?

Yes.

Ian

References:
- Re: Effect of 'register' keyword on debug info
  - From: Rohit Arul Raj
- Re: Effect of 'register' keyword on debug info
  - From: Ian Lance Taylor
- Re: Effect of 'register' keyword on debug info
  - From: Rohit Arul Raj

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