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Re: Fw: Possible missed optimization opportunity with const?

From: Florian Weimer <fweimer at redhat dot com>
To: Toshi Morita <tm314159 at yahoo dot com>, David Brown <david at westcontrol dot com>
Cc: "gcc-help at gcc dot gnu dot org" <gcc-help at gcc dot gnu dot org>
Date: Thu, 1 Sep 2016 21:19:37 +0200
Subject: Re: Fw: Possible missed optimization opportunity with const?
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References: <848378447.3130483.1472699334626.ref@mail.yahoo.com> <848378447.3130483.1472699334626@mail.yahoo.com> <57C7F6C6.1020102@westcontrol.com> <115067949.3431131.1472753492632@mail.yahoo.com> <57C87B59.3090207@westcontrol.com> <1650095493.3446818.1472757080483@mail.yahoo.com>

On 09/01/2016 09:11 PM, Toshi Morita wrote:

I suspect when the C front-end parses (const int * const)0x1234, it fails
to apply the const_tree attribute to the subtree, and this is why the
optimization is failing.

The optimization is not failing—it results in *invalid code* if thecompiler cannot observe that the pointer points to a const object. Forpointers, const does not mean immutable.


Florian

References:
- Re: Fw: Possible missed optimization opportunity with const?
  - From: Toshi Morita
- Re: Fw: Possible missed optimization opportunity with const?
  - From: David Brown
- Re: Fw: Possible missed optimization opportunity with const?
  - From: Toshi Morita
- Re: Fw: Possible missed optimization opportunity with const?
  - From: David Brown
- Re: Fw: Possible missed optimization opportunity with const?
  - From: Toshi Morita

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