On 4/23/2017 9:55 PM, Jiri Olsa wrote:

On Thu, Apr 20, 2017 at 08:07:50PM +0800, Jin Yao wrote:

SNIP

quoted

  
+#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?

quoted

+
+	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

quoted

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