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    SubjectRe: [PATCH v6 2/7] perf/x86/intel: Record branch type
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    On 4/23/2017 9:55 PM, Jiri Olsa wrote:
    > On Thu, Apr 20, 2017 at 08:07:50PM +0800, Jin Yao wrote:
    >
    > SNIP
    >
    >>
    >> +#define X86_BR_TYPE_MAP_MAX 16
    >> +
    >> +static int
    >> +common_branch_type(int type)
    >> +{
    >> + int i, mask;
    >> + const int branch_map[X86_BR_TYPE_MAP_MAX] = {
    >> + PERF_BR_CALL, /* X86_BR_CALL */
    >> + PERF_BR_RET, /* X86_BR_RET */
    >> + PERF_BR_SYSCALL, /* X86_BR_SYSCALL */
    >> + PERF_BR_SYSRET, /* X86_BR_SYSRET */
    >> + PERF_BR_INT, /* X86_BR_INT */
    >> + PERF_BR_IRET, /* X86_BR_IRET */
    >> + PERF_BR_JCC, /* X86_BR_JCC */
    >> + PERF_BR_JMP, /* X86_BR_JMP */
    >> + PERF_BR_IRQ, /* X86_BR_IRQ */
    >> + PERF_BR_IND_CALL, /* X86_BR_IND_CALL */
    >> + PERF_BR_NONE, /* X86_BR_ABORT */
    >> + PERF_BR_NONE, /* X86_BR_IN_TX */
    >> + PERF_BR_NONE, /* X86_BR_NO_TX */
    >> + PERF_BR_CALL, /* X86_BR_ZERO_CALL */
    >> + PERF_BR_NONE, /* X86_BR_CALL_STACK */
    >> + PERF_BR_IND_JMP, /* X86_BR_IND_JMP */
    >> + };
    >> +
    >> + type >>= 2; /* skip X86_BR_USER and X86_BR_KERNEL */
    >> + mask = ~(~0 << 1);
    > is that a fancy way to get 1 into the mask? what do I miss?
    >
    >> +
    >> + for (i = 0; i < X86_BR_TYPE_MAP_MAX; i++) {
    >> + if (type & mask)
    >> + return branch_map[i];
    > I wonder some bit search would be faster in here, but maybe not big deal
    >
    > jirka

    I just think the branch_map[] doesn't contain many entries (16 entries
    here), so maybe checking 1 bit one time should be acceptable. I just
    want to keep the code simple.

    But if the number of entries is more (e.g. 64), maybe it'd better check
    2 or 4 bits one time.

    Thanks
    Jin Yao

    >
    >> +
    >> + type >>= 1;
    >> + }
    >> +
    >> + return PERF_BR_NONE;
    >> +}
    >> +
    >> /*

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