macro.h: provide a switch-case statement generator for IN_SET

Rather than walking a list of valid values one-by-one, generate a
switch-case statement for the IN_SET() macro. This allows the compiler to
further optimize its code output, possibly by generating jump tables.
This effectively decreases the binary size slightly.

The implementation is based on macro overloading depending on the number of
arguments. h/t to the following post:

  https://stackoverflow.com/questions/11761703/overloading-macro-on-number-of-arguments

diff --git a/src/basic/macro.h b/src/basic/macro.h
index 5088e6720d8640e8e13c1d58e7c74a1da7ff9423..c529c6ecade118cd4a83552251930f28febd1d28 100644 (file)
--- a/src/basic/macro.h
+++ b/src/basic/macro.h
@@ -320,18 +320,47 @@ static inline unsigned long ALIGN_POWER2(unsigned long u) {
 #define SET_FLAG(v, flag, b) \
         (v) = (b) ? ((v) | (flag)) : ((v) & ~(flag))
 
-#define IN_SET(x, y, ...)                                               \
-        ({                                                              \
-                static const typeof(y) _array[] = { (y), __VA_ARGS__ }; \
-                const typeof(y) _x = (x);                               \
-                unsigned _i;                                            \
-                bool _found = false;                                    \
-                for (_i = 0; _i < ELEMENTSOF(_array); _i++)             \
-                        if (_array[_i] == _x) {                         \
-                                _found = true;                          \
-                                break;                                  \
-                        }                                               \
-                _found;                                                 \
+#define CASE_F(X) case X:
+#define CASE_F_1(CASE, X) CASE_F(X)
+#define CASE_F_2(CASE, X, ...)  CASE(X) CASE_F_1(CASE, __VA_ARGS__)
+#define CASE_F_3(CASE, X, ...)  CASE(X) CASE_F_2(CASE, __VA_ARGS__)
+#define CASE_F_4(CASE, X, ...)  CASE(X) CASE_F_3(CASE, __VA_ARGS__)
+#define CASE_F_5(CASE, X, ...)  CASE(X) CASE_F_4(CASE, __VA_ARGS__)
+#define CASE_F_6(CASE, X, ...)  CASE(X) CASE_F_5(CASE, __VA_ARGS__)
+#define CASE_F_7(CASE, X, ...)  CASE(X) CASE_F_6(CASE, __VA_ARGS__)
+#define CASE_F_8(CASE, X, ...)  CASE(X) CASE_F_7(CASE, __VA_ARGS__)
+#define CASE_F_9(CASE, X, ...)  CASE(X) CASE_F_8(CASE, __VA_ARGS__)
+#define CASE_F_10(CASE, X, ...) CASE(X) CASE_F_9(CASE, __VA_ARGS__)
+#define CASE_F_11(CASE, X, ...) CASE(X) CASE_F_10(CASE, __VA_ARGS__)
+#define CASE_F_12(CASE, X, ...) CASE(X) CASE_F_11(CASE, __VA_ARGS__)
+#define CASE_F_13(CASE, X, ...) CASE(X) CASE_F_12(CASE, __VA_ARGS__)
+#define CASE_F_14(CASE, X, ...) CASE(X) CASE_F_13(CASE, __VA_ARGS__)
+#define CASE_F_15(CASE, X, ...) CASE(X) CASE_F_14(CASE, __VA_ARGS__)
+#define CASE_F_16(CASE, X, ...) CASE(X) CASE_F_15(CASE, __VA_ARGS__)
+#define CASE_F_17(CASE, X, ...) CASE(X) CASE_F_16(CASE, __VA_ARGS__)
+#define CASE_F_18(CASE, X, ...) CASE(X) CASE_F_17(CASE, __VA_ARGS__)
+#define CASE_F_19(CASE, X, ...) CASE(X) CASE_F_18(CASE, __VA_ARGS__)
+#define CASE_F_20(CASE, X, ...) CASE(X) CASE_F_19(CASE, __VA_ARGS__)
+
+#define GET_CASE_F(_1,_2,_3,_4,_5,_6,_7,_8,_9,_10,_11,_12,_13,_14,_15,_16,_17,_18,_19,_20,NAME,...) NAME
+#define FOR_EACH_MAKE_CASE(...) \
+        GET_CASE_F(__VA_ARGS__,CASE_F_20,CASE_F_19,CASE_F_18,CASE_F_17,CASE_F_16,CASE_F_15,CASE_F_14,CASE_F_13,CASE_F_12,CASE_F_11, \
+                               CASE_F_10,CASE_F_9,CASE_F_8,CASE_F_7,CASE_F_6,CASE_F_5,CASE_F_4,CASE_F_3,CASE_F_2,CASE_F_1) \
+                   (CASE_F,__VA_ARGS__)
+
+#define IN_SET(x, ...)                          \
+        ({                                      \
+                bool _found = false;            \
+                /* If the build breaks in the line below, you need to extend the case macros */ \
+                static _unused_ char _static_assert__macros_need_to_be_extended[20 - sizeof((int[]){__VA_ARGS__})/sizeof(int)]; \
+                switch(x) {                     \
+                FOR_EACH_MAKE_CASE(__VA_ARGS__) \
+                        _found = true;          \
+                        break;                  \
+                default:                        \
+                        break;                  \
+                }                               \
+                _found;                         \
         })
 
 /* Define C11 thread_local attribute even on older gcc compiler