gfphoenix78 commented on code in PR #1467:
URL: https://github.com/apache/cloudberry/pull/1467#discussion_r2587683182
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contrib/udp2/ic_common/udp2/ic_udp2_internal.hpp:
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@@ -63,6 +66,21 @@
namespace {
+/*
+ * Hints to the compiler about the likelihood of a branch. Both likely() and
+ * unlikely() return the boolean value of the contained expression.
+ *
+ * These should only be used sparingly, in very hot code paths. It's very easy
+ * to mis-estimate likelihoods.
+ */
+#if __GNUC__ >= 3
+#define likely(x) __builtin_expect((x) != 0, 1)
+#define unlikely(x) __builtin_expect((x) != 0, 0)
+#else
+#define likely(x) ((x) != 0)
+#define unlikely(x) ((x) != 0)
+#endif
+
Review Comment:
`likely` and `unlikely` are already defined in `c.h`. It's better not
defined in another header file.
If you prefer not include the header `c.h` in the source file, better define
these macros inside the source file.
It's unpredictable that if someone include both of the two headers, which
will cause error for redefined macros.
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