Sanitize dump payload: performance optimizations and tuning

First, if the ziplist header is surely inside the ziplist, do fast path
decoding rather than the careful one.

In that case, streamline the encoding if-else chain to be executed only
once, and the encoding validity tested at the end.

encourage inlining

likely / unlikely hints for speculative execution

Assertion used _exit(1) to tell the compiler that the code after them is
not reachable and get rid of warnings.

But in some cases assertions are placed inside tight loops, and any
piece of code in them can slow down execution (code cache and other
reasons), instead using either abort() or better yet, unreachable
builtin.

1 files changed, 14 insertions, 0 deletions

diff --git a/src/config.h b/src/config.h
index 2cd44f927..b8723e7ce 100644
--- a/src/config.h
+++ b/src/config.h
@@ -97,6 +97,20 @@
 #define redis_fsync fsync
 #endif
 
+#if __GNUC__ >= 4
+#define redis_unreachable __builtin_unreachable
+#else
+#define redis_unreachable abort
+#endif
+
+#if __GNUC__ >= 3
+#define likely(x) __builtin_expect(!!(x), 1)
+#define unlikely(x) __builtin_expect(!!(x), 0)
+#else
+#define likely(x) (x)
+#define unlikely(x) (x)
+#endif
+
 /* Define rdb_fsync_range to sync_file_range() on Linux, otherwise we use
  * the plain fsync() call. */
 #ifdef __linux__