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    SubjectRe: PGCC and the kernel
    John Twilley wrote:

    Hello John,

    > I'm using the newest version of PGCC I can find. Here's the version
    > string:
    > gcc driver version 2.7.2p snapshot 970522 executing gcc version 2.7.2p
    The latest version is pgcc snapshot 970721
    but 970522 is OK too ;-)

    > I'd like to know if there are any tweaks I should make to kernel
    > makefiles other than changing '-O2' to '-O6 -frisc'.
    > Also, the kernel compiles fine except for arch/i386/lib/checksum.c,
    > where it fails with this error:
    > gcc -D__KERNEL__ -I/usr/src/linux/include -Wall -Wno-sign-compare
    > -Wstrict-prototypes -O5 -frisc -fomit-frame-pointer -D__SMP__ -pipe
    > -fno-strength-reduce -mpentium -malign-loops=2 -malign-jumps=2
    > -malign-functions=2 -DCPU=586 -D__SMP__ -c -o checksum.o checksum.c
    > {standard input}: Assembler messages:
    > {standard input}:509: Fatal error: Symbol end_of_body already defined.
    > It compiles fine with -O2. I'm going to try all the different
    > optimizations between -O2 and -O6 just to see what's breaking, and
    > report it to the PGCC crew. Has anyone else noticed this?

    Here's what I did:

    1. change CFLAGS in toplevel Makefile to simply -O6
    (-frisc and -fomit-frame-pointer are included in this O-Level !)
    The -fno-inline-functions is a workaround for the "checksum.c" -
    Problem, there is no decrease in performance, because the Kernel uses
    mostly explizit inline Statements B-)

    2. in arch/i386/Makefile change CFLAGS to -mpentium -DCPU586 and
    remove -fno-strength-reduce (pgcc has this bug fixed). The
    alignment options are not necessary, the pgcc uses the best
    (zero) alignment per default.

    3. The compiler generates a lot of warnings about signed/unsigned
    comparison, if you don't like this, add -Wno-sign-compare after
    -Wall to the CFLAGS.

    I have no problems with the pgcc and Linux since I used them together,
    the System runs stable. One interesting thing would be the performance
    increase (if there is one), maybe you could run some benchmarks
    (eg lmbench), i haven't done this so far (sorry).

    Hope this helps


    PS: Thanks to the pgcc and linux guys, I (and my K6) love both ;-)

    * Frank Heldt
    * ===> Linux for IQ's higher than 95 <===
    * +49 0551/7073-511

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