https://gcc.gnu.org/g:fb72a86ac10d8a005fb6919d0d0bba8457c2b7fd
commit fb72a86ac10d8a005fb6919d0d0bba8457c2b7fd Author: Alexandre Oliva <[email protected]> Date: Fri Nov 28 02:01:18 2025 -0300 hard-reg-set: use ctz for iteration Simplify the HARD_REG_SET iteration, using ctz and avoiding some unnecessary operations. for gcc/ChangeLog * hard-reg-set.h (hard_reg_set_iter_init): Drop unnecessary increment of min. (hard_reg_set_iter_set): Use ctz_hwi, and compute word-advanced regno from word_no. (hard_reg_set_iter_next): Only clear the cached LSB. Diff: --- gcc/hard-reg-set.h | 31 ++++++++++++------------------- 1 file changed, 12 insertions(+), 19 deletions(-) diff --git a/gcc/hard-reg-set.h b/gcc/hard-reg-set.h index e33c8e334d39..ab1f3b9cafab 100644 --- a/gcc/hard-reg-set.h +++ b/gcc/hard-reg-set.h @@ -342,8 +342,8 @@ struct hard_reg_set_iterator #define HARD_REG_ELT_BITS UHOST_BITS_PER_WIDE_INT -/* The implementation of the iterator functions is fully analogous to - the bitmap iterators. */ +/* The implementation of the iterator functions is a simplified version of + those of bitmap iterators. */ inline void hard_reg_set_iter_init (hard_reg_set_iterator *iter, const_hard_reg_set set, unsigned min, unsigned *regno) @@ -360,9 +360,6 @@ hard_reg_set_iter_init (hard_reg_set_iterator *iter, const_hard_reg_set set, { iter->bits = iter->pelt[iter->word_no]; iter->bits >>= min % HARD_REG_ELT_BITS; - - /* This is required for correct search of the next bit. */ - min += !iter->bits; } *regno = min; } @@ -378,37 +375,33 @@ hard_reg_set_iter_set (hard_reg_set_iterator *iter, unsigned *regno) if (iter->bits) { - /* Find the correct bit and return it. */ - while (!(iter->bits & 1)) - { - iter->bits >>= 1; - *regno += 1; - } + unsigned skip = ctz_hwi (iter->bits); + iter->bits >>= skip; + *regno += skip; return (*regno < FIRST_PSEUDO_REGISTER); } - /* Round to the beginning of the next word. */ - *regno = (*regno + HARD_REG_ELT_BITS - 1); - *regno -= *regno % HARD_REG_ELT_BITS; - /* Find the next non-zero word. */ while (++iter->word_no < iter->length) { iter->bits = iter->pelt[iter->word_no]; if (iter->bits) break; - *regno += HARD_REG_ELT_BITS; } + + *regno = iter->word_no * HARD_REG_ELT_BITS; } } inline void -hard_reg_set_iter_next (hard_reg_set_iterator *iter, unsigned *regno) +hard_reg_set_iter_next (hard_reg_set_iterator *iter, unsigned *) { - iter->bits >>= 1; - *regno += 1; + /* Only clear the bit, so that we skip it in iter_set. */ + iter->bits &= ~ HARD_CONST (1); } +/* SET must not change throughout the iteration. + REGNUM (and ITER) may only be changed by the iteration functions. */ #define EXECUTE_IF_SET_IN_HARD_REG_SET(SET, MIN, REGNUM, ITER) \ for (hard_reg_set_iter_init (&(ITER), (SET), (MIN), &(REGNUM)); \ hard_reg_set_iter_set (&(ITER), &(REGNUM)); \
