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Re: GCC optimizes integer overflow: bug or feature?
From: |
Paul Brook |
Subject: |
Re: GCC optimizes integer overflow: bug or feature? |
Date: |
Fri, 22 Dec 2006 02:03:23 +0000 |
User-agent: |
KMail/1.9.5 |
On Friday 22 December 2006 00:58, Denis Vlasenko wrote:
> On Tuesday 19 December 2006 23:39, Denis Vlasenko wrote:
> > There are a lot of 100.00% safe optimizations which gcc
> > can do. Value range propagation for bitwise operations, for one
>
> Or this, absolutely typical C code. i386 arch can compare
> 16 bits at a time here (luckily, no alighment worries on this arch):
>
> int f(char *p)
> {
> if (p[0] == 1 && p[1] == 2) return 1;
> return 0;
> }
Definitely not 100% safe. p may point to memory that is sensitive to the
access width and/or number of accesses. (ie. memory mapped IO).
Paul
- Re: GCC optimizes integer overflow: bug or feature?, (continued)
- Re: GCC optimizes integer overflow: bug or feature?, Gabriel Dos Reis, 2006/12/20
- Message not available
- Re: GCC optimizes integer overflow: bug or feature?, Ian Lance Taylor, 2006/12/20
- Re: GCC optimizes integer overflow: bug or feature?, Zdenek Dvorak, 2006/12/20
- Re: GCC optimizes integer overflow: bug or feature?, Robert Dewar, 2006/12/20
- Re: GCC optimizes integer overflow: bug or feature?, Denis Vlasenko, 2006/12/20
- Re: GCC optimizes integer overflow: bug or feature?, Paul Brook, 2006/12/20
- Re: GCC optimizes integer overflow: bug or feature?, Denis Vlasenko, 2006/12/21
- Re: GCC optimizes integer overflow: bug or feature?,
Paul Brook <=
- Re: GCC optimizes integer overflow: bug or feature?, Robert Dewar, 2006/12/21
- Re: GCC optimizes integer overflow: bug or feature?, Paul Brook, 2006/12/21
- Re: GCC optimizes integer overflow: bug or feature?, Robert Dewar, 2006/12/21
- Re: GCC optimizes integer overflow: bug or feature?, Denis Vlasenko, 2006/12/22
- RE: GCC optimizes integer overflow: bug or feature?, Dave Korn, 2006/12/22
- RE: GCC optimizes integer overflow: bug or feature?, Andrew Pinski, 2006/12/22
- Re: GCC optimizes integer overflow: bug or feature?, Robert Dewar, 2006/12/22
- Re: GCC optimizes integer overflow: bug or feature?, Andrew Pinski, 2006/12/22
- Re: GCC optimizes integer overflow: bug or feature?, Robert Dewar, 2006/12/22
- Re: GCC optimizes integer overflow: bug or feature?, Rask Ingemann Lambertsen, 2006/12/23