Messages in this thread | | | Subject | Re: [PATCH v8 2/7] perf/x86/intel: Record branch type | From | "Jin, Yao" <> | Date | Thu, 13 Jul 2017 22:53:04 +0800 |
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On 7/13/2017 10:31 PM, Peter Zijlstra wrote: > On Thu, Jul 13, 2017 at 08:04:14PM +0800, Jin Yao wrote: >> +#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_UNKNOWN, /* X86_BR_INT */ >> + PERF_BR_UNKNOWN, /* X86_BR_IRET */ >> + PERF_BR_COND, /* X86_BR_JCC */ >> + PERF_BR_UNCOND, /* X86_BR_JMP */ >> + PERF_BR_UNKNOWN, /* X86_BR_IRQ */ >> + PERF_BR_IND_CALL, /* X86_BR_IND_CALL */ >> + PERF_BR_UNKNOWN, /* X86_BR_ABORT */ >> + PERF_BR_UNKNOWN, /* X86_BR_IN_TX */ >> + PERF_BR_UNKNOWN, /* X86_BR_NO_TX */ >> + PERF_BR_CALL, /* X86_BR_ZERO_CALL */ >> + PERF_BR_UNKNOWN, /* X86_BR_CALL_STACK */ >> + PERF_BR_IND, /* X86_BR_IND_JMP */ >> + }; >> + >> + type >>= 2; /* skip X86_BR_USER and X86_BR_KERNEL */ > >> + mask = ~(~0 << 1); > OCC worthy means of writing: 1 Yes, mask = 1. I just want to represent the bit 0 of mask is 1. >> + >> + for (i = 0; i < X86_BR_TYPE_MAP_MAX; i++) { >> + if (type & mask) >> + return branch_map[i]; >> + >> + type >>= 1; >> + } > That is some of the more confused code I've seen in a while :/ > > if (type) > return branch_map[__ffs(type)]; > > is what you meant to write, no?
Not write, I just want to return the element of branch_map[].
The input type is one of X86_BR and the X86_BR is:
X86_BR_CALL = 1 << 2, /* call */ X86_BR_RET = 1 << 3, /* return */ X86_BR_SYSCALL = 1 << 4, /* syscall */ X86_BR_SYSRET = 1 << 5, /* syscall return */ X86_BR_INT = 1 << 6, /* sw interrupt */ X86_BR_IRET = 1 << 7, /* return from interrupt */ X86_BR_JCC = 1 << 8, /* conditional */ X86_BR_JMP = 1 << 9, /* jump */ X86_BR_IRQ = 1 << 10,/* hw interrupt or trap or fault */ X86_BR_IND_CALL = 1 << 11,/* indirect calls */ X86_BR_ABORT = 1 << 12,/* transaction abort */ X86_BR_IN_TX = 1 << 13,/* in transaction */ X86_BR_NO_TX = 1 << 14,/* not in transaction */ X86_BR_ZERO_CALL = 1 << 15,/* zero length call */ X86_BR_CALL_STACK = 1 << 16,/* call stack */ X86_BR_IND_JMP = 1 << 17,/* indirect jump */
Lookup the table to get the common branch type.
Sorry, what is the __ffs()?
Thanks Jin Yao
>> + >> + return PERF_BR_UNKNOWN; >> +}
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