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    SubjectRe: Want comments regarding patch

    On Dec 28 2006 19:53, Arjan van de Ven wrote:
    >On Thu, 2006-12-28 at 19:41 +0100, Daniel Marjamäki wrote:
    >> Hello all!
    >> I sent a patch with this content:
    >> - for (i = 0; i < MAX_PIRQS; i++)
    >> - pirq_entries[i] = -1;
    >> + memset(pirq_entries, -1, sizeof(pirq_entries));
    >> I'd like to know if you have any comments to this change. It was
    >> of course my intention to make the code shorter, simpler and
    >> faster.
    >personally I don't like the new code; memset only takes a byte as
    >argument and while it probably is the same, that is now implicit
    >behavior and no longer explicit. A reasonably good compiler will
    >notice it's the same and generate the best code anyway, so I would
    >really really suggest to go for the best readable code, which imo is
    >the original code.

    Then GCC is not a "reasonably good compiler". Considering

    #define MAX 6400
    struct foo {
    int line[MAX];
    void bar(struct foo *a) {
    int i;
    for(i = 0; i < MAX; ++i)
    a->line[i] = -1;
    void baz(struct foo *a) {
    __builtin_memset(a->line, -1, sizeof(a->line));

    `gcc -O3 -c test.c` will generate a classic loop rather than a repz
    movsd for bar(). baz() will get a call to an extern memset(),
    probably because gcc could not figure out how to make a repz for it
    and hence thought it was better to use an external hand-crafted

     \ /
      Last update: 2006-12-29 00:55    [W:0.021 / U:0.732 seconds]
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