The macro BITMAP_LAST_WORD_MASK can be implemented without a conditional, which will generally lead to slightly better generated code (221 bytes saved for allmodconfig-GCOV_KERNEL, ~2k with GCOV_KERNEL). As a small bonus, this also ensures that the nbits parameter is expanded exactly once. In BITMAP_FIRST_WORD_MASK, if start is signed gcc is technically allowed to assume it is positive (or divisible by BITS_PER_LONG), and hence just do the simple mask. It doesn't seem to use this, and even on an architecture like x86 where the shift only depends on the lower 5 or 6 bits, and these bits are not affected by the signedness of the expression, gcc still generates code to compute the C99 mandated value of start % BITS_PER_LONG. So just use a mask explicitly, also for consistency with BITMAP_LAST_WORD_MASK.
Unified · Split
| @@ -172,12 +172,8 @@ extern unsigned int bitmap_ord_to_pos(const unsigned long *bitmap, unsigned int · 171 unmodified lines | |||
| 172 | extern int bitmap_print_to_pagebuf(bool list, char *buf, | 172 | extern int bitmap_print_to_pagebuf(bool list, char *buf, |
| 173 | const unsigned long *maskp, int nmaskbits); | 173 | const unsigned long *maskp, int nmaskbits); |
| 174 | 174 | ||
| 175 | #define BITMAP_FIRST_WORD_MASK(start) (~0UL << ((start) % BITS_PER_LONG)) | 175 | #define BITMAP_FIRST_WORD_MASK(start) (~0UL << ((start) & (BITS_PER_LONG - 1))) |
| 176 | #define BITMAP_LAST_WORD_MASK(nbits) \ | 176 | #define BITMAP_LAST_WORD_MASK(nbits) (~0UL >> (-(nbits) & (BITS_PER_LONG - 1))) |
| 177 | ( \ | ||
| 178 | ((nbits) % BITS_PER_LONG) ? \ | ||
| 179 | (1UL<<((nbits) % BITS_PER_LONG))-1 : ~0UL \ | ||
| 180 | ) | ||
| 181 | 177 | ||
| 182 | #define small_const_nbits(nbits) \ | 178 | #define small_const_nbits(nbits) \ |
| 183 | (__builtin_constant_p(nbits) && (nbits) <= BITS_PER_LONG) | 179 | (__builtin_constant_p(nbits) && (nbits) <= BITS_PER_LONG) |