DragonFly BSD
DragonFly kernel List (threaded) for 2004-05
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Re: kernel broken using CPUTYPE and 2.95.4

From: Matthew Dillon <dillon@xxxxxxxxxxxxxxxxxxxx>
Date: Mon, 10 May 2004 08:28:28 -0700 (PDT)

:I don't think theres anyway we can support the P4 option any time soon 
:and I know that theres no chance of it working under gcc 2.95.

    I agree.  Trying to use cpu-specific optimizations in 2.95.x is roughly 
    equivalent to a blind man driving an 18 wheeler down the highway.  
    In other words: "don't do it, it doesn't work".  GCC2 is known to 
    produce bad code not only with CPUTYPE, but also with higher 
    optimization levels like -O2.  Blame the GCC folks for this.

    GCC3 does a better job but even so I would not use CPUTYPE without being
    prepared to turn it off when something breaks, and at best I might use
    -O2 or -Os (under GCC3 only, and even then we don't really officially
    support it, since differentiating between compiler code generation bugs
    and DFly bugs is extremely difficult).

    Besides, you won't notice any improvement in kernel performance.

					Matthew Dillon 

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