1 #define EXPAND_2_INNER_CASES(i, x, y) INNER_CASE(i, x, y); INNER_CASE(i + 1, x, y); 2 #define EXPAND_4_INNER_CASES(i, x, y) EXPAND_2_INNER_CASES(i, x, y) EXPAND_2_INNER_CASES(i + 2, x, y) 3 #define EXPAND_8_INNER_CASES(i, x, y) EXPAND_4_INNER_CASES(i, x, y) EXPAND_4_INNER_CASES(i + 4, x, y) 4 #define EXPAND_16_INNER_CASES(i, x, y) EXPAND_8_INNER_CASES(i, x, y) EXPAND_8_INNER_CASES(i + 8, x, y) 5 #define EXPAND_32_INNER_CASES(i, x, y) EXPAND_16_INNER_CASES(i, x, y) EXPAND_16_INNER_CASES(i + 16, x, y) 6 #define EXPAND_64_INNER_CASES(i, x, y) EXPAND_32_INNER_CASES(i, x, y) EXPAND_32_INNER_CASES(i + 32, x, y) 7 8 #define EXPAND_2_OUTER_CASES(i, x, y) OUTER_CASE(i, x, y); OUTER_CASE(i + 1, x, y); 9 #define EXPAND_4_OUTER_CASES(i, x, y) EXPAND_2_OUTER_CASES(i, x, y) EXPAND_2_OUTER_CASES(i + 2, x, y) 10 #define EXPAND_8_OUTER_CASES(i, x, y) EXPAND_4_OUTER_CASES(i, x, y) EXPAND_4_OUTER_CASES(i + 4, x, y) 11 #define EXPAND_16_OUTER_CASES(i, x, y) EXPAND_8_OUTER_CASES(i, x, y) EXPAND_8_OUTER_CASES(i + 8, x, y) 12 #define EXPAND_32_OUTER_CASES(i, x, y) EXPAND_16_OUTER_CASES(i, x, y) EXPAND_16_OUTER_CASES(i + 16, x, y) 13 #define EXPAND_64_OUTER_CASES(i, x, y) EXPAND_32_OUTER_CASES(i, x, y) EXPAND_32_OUTER_CASES(i + 32, x, y) 14 15 // Rather than a single monstrous fan-out, this fans out in smaller increments, 16 // but to a similar size. 17 unsigned cfg_nested_switch(int x) { 18 unsigned y = 0; 19 while (x > 0) { 20 switch (x) { 21 #define INNER_CASE(i, x, y) \ 22 case i: { int case_var = 3*x + i; y += case_var - 1; break; } 23 #define OUTER_CASE(i, x, y) \ 24 case i: { \ 25 int case_var = y >> 8; \ 26 switch (case_var) { \ 27 EXPAND_64_INNER_CASES(0, x, y); \ 28 } \ 29 break; \ 30 } 31 EXPAND_64_OUTER_CASES(0, x, y); 32 } 33 --x; 34 } 35 return y; 36 } 37
