Re: -O2 vs -O3

From: Dave Jones (dave@denial.force9.co.uk)
Date: Wed May 24 2000 - 14:13:22 EDT

  • Next message: Ed Tomlinson: "ide-tape flaky in 2.2.15"

    Christopher Thompson <chris@hypocrite.org> wrote:
    > Linux kernels are compiled with the -O2 flag set. I'm curious, why don't we
    > use -O3?

    During the early development of Powertweak I set the Makefile files to compile
    some routines with -O3 instead of -O2. I then spent hours looking for a bug
    which wasn't there. The optimiser was over-zealous, and removed a pointer
    assignment.

    So I guess -O2 implies that we use only the known-to-be-safe optimisations.

    On a sidenote, the optimiser in egcs 2.91.66 still generates bugged code in some
    situations which can only be worked around by setting -O0
    (Example available upon request)

    regards,

    -- 
    Dave.
    

    - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.rutgers.edu Please read the FAQ at http://www.tux.org/lkml/



    This archive was generated by hypermail 2b29 : Thu May 25 2000 - 07:27:28 EDT