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;
+}
