From owner-freebsd-hackers  Sat Mar 13 15:38:12 1999
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Date: Sun, 14 Mar 1999 00:37:04 +0100 (CET)
From: Remy Nonnenmacher <remy@synx.com>
Reply-To: remy@synx.com
Subject: Re: 'C' language question
To: dennis@etinc.com
Cc: hackers@FreeBSD.ORG
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On 13 Mar, Dennis wrote:
> *reg |= 0x80000000;
> 
> generates a byte OR (ORB instruction) which trashes the register with
> gcc 2.9.2....a stupid "optimization" that happens to be wrong in this
> case.

Just for fun: i couldn't resist to expose you all a real 'optimization'
madness of the C compiler of a big (really big) company :

(after macros expension)

Original :

   if (A == 0) {...}
   if ((A == 0 ? *ptr++ : func()) == 7) {...}

assembler code generated :

   if (A == 0) {..}
   else if (*++ptr == 7) {..}
             ^^^^^

just to say that 'stupid' seems a little hard in the original
message case.

RN.








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