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Date: Mon, 25 Jun 2007 17:15:08 +0200
From: Ed Schouten <ed@fxq.nl>
To: Andrey Chernov <ache@nagual.pp.ru>, Alexander Kabaev <kabaev@gmail.com>,
	current@freebsd.org, kan@freebsd.org
Message-ID: <20070625151508.GO27942@hoeg.nl>
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Subject: Re: Silent gcc 4.2.0 loop optimization bug with -O2
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Hello Andrey,

* Andrey Chernov <ache@nagual.pp.ru> wrote:
> Well... Is this small enough?

I did some more stripping and it turns out this is the problem

| int
| main(int argc, char *argv[])
| {
|         int i;
|         int numbers[4] =3D { 0xdead, 0xbeef, 0x1337, 0x4242 };
|=20
|         for (i =3D 1; i <=3D 12; i++) {
|                 if (i <=3D 4)
|                         printf("%d: %x\n", i, numbers[i-1]);
|                 else if (i >=3D 7 && i <=3D 9)
|                         printf("MUST BE HERE!!! %d\n", i);
|         }
| }

When you increase the size of the array to 6 or higher, it does what you
want. It clearly looks like a compiler bug; the size of the array
shouldn't have an effect on the amount of iterations.=20

You should really file a bug at GCC's to make sure this gets fixed in
4.2.1.

Yours,
--=20
 Ed Schouten <ed@fxq.nl>
 WWW: http://g-rave.nl/

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