YT-23346: Introduce YT_ASSUME and YT_UNREACHABLE macros.

Y_ASSUME and Y_UNREACHABLE macros are platform-independent ways to
give a hint for a compiler about some value or state. Compilier may
use that hint for optimization. On the other hand if the hint is
wrong it may lead to undefined behavior.

YT_ASSUME and YT_UNREACHABLE are wrappers around Y_ASSUME and
Y_UNREACHABLE that actually check that the hint is correct in
debug build. That introduces some code safety and at the same time
allows certain optimization in optimized build.
commit_hash:2d0969361910a10a870bae226d838d494e656edb

Author: thenewone

library/cpp/yt/assert/assert.h

@@ -55,6 +55,20 @@ void AssertTrapImpl(
         } \
     } while (false)
 
+//! Behaves as |YT_ASSERT| in debug mode and as |Y_ASSUME| in release.
+#ifdef NDEBUG
+    #define YT_ASSUME(expr) Y_ASSUME(expr)
+#else
+    #define YT_ASSUME(expr) YT_ASSERT(expr)
+#endif
+
+//! Behaves as |YT_ASSERT(false)| in debug mode and as |Y_UNREACHABLE| in release.
+#ifdef NDEBUG
+    #define YT_UNREACHABLE() Y_UNREACHABLE()
+#else
+    #define YT_UNREACHABLE() YT_ASSERT(false)
+#endif
+
 //! Fatal error code marker. Abnormally terminates the current process.
 #ifdef YT_COMPILING_UDF
     #define YT_ABORT() __YT_BUILTIN_ABORT()