Re: [PATCH v8 4/7] stdlib: qsort: Move some macros to inline function

[Noah Goldstein <goldstein.w.n@gmail.com>]

On Tue, Oct 3, 2023 at 7:23 AM Adhemerval Zanella
<adhemerval.zanella@linaro.org> wrote:
>
> ---
>  stdlib/qsort.c | 35 +++++++++++++++++++++++------------
>  1 file changed, 23 insertions(+), 12 deletions(-)
>
> diff --git a/stdlib/qsort.c b/stdlib/qsort.c
> index 5691249a9b..80706b3357 100644
> --- a/stdlib/qsort.c
> +++ b/stdlib/qsort.c
> @@ -100,15 +100,28 @@ typedef struct
>      char *hi;
>    } stack_node;
>
> -/* The next 4 #defines implement a very fast in-line stack abstraction. */
>  /* The stack needs log (total_elements) entries (we could even subtract
>     log(MAX_THRESH)).  Since total_elements has type size_t, we get as
>     upper bound for log (total_elements):
>     bits per byte (CHAR_BIT) * sizeof(size_t).  */
> -#define STACK_SIZE     (CHAR_BIT * sizeof (size_t))
> -#define PUSH(low, high)        ((void) ((top->lo = (low)), (top->hi = (high)), ++top))
> -#define        POP(low, high)  ((void) (--top, (low = top->lo), (high = top->hi)))
> -#define        STACK_NOT_EMPTY (stack < top)
> +enum { STACK_SIZE = CHAR_BIT * sizeof (size_t) };
> +
> +static inline stack_node *
> +push (stack_node *top, char *lo, char *hi)
> +{
> +  top->lo = lo;
> +  top->hi = hi;
> +  return ++top;
> +}
> +
> +static inline stack_node *
> +pop (stack_node *top, char **lo, char **hi)
> +{
> +  --top;
> +  *lo = top->lo;
> +  *hi = top->hi;
> +  return top;
> +}
>
>
>  static inline void
> @@ -212,11 +225,9 @@ _quicksort (void *const pbase, size_t total_elems, size_t size,
>        char *lo = base_ptr;
>        char *hi = &lo[size * (total_elems - 1)];
>        stack_node stack[STACK_SIZE];
> -      stack_node *top = stack;
> -
> -      PUSH (NULL, NULL);
> +      stack_node *top = stack + 1;
>
> -      while (STACK_NOT_EMPTY)
> +      while (stack < top)
>          {
>            char *left_ptr;
>            char *right_ptr;
> @@ -281,7 +292,7 @@ _quicksort (void *const pbase, size_t total_elems, size_t size,
>              {
>                if ((size_t) (hi - left_ptr) <= max_thresh)
>                 /* Ignore both small partitions. */
> -                POP (lo, hi);
> +                top = pop (top, &lo, &hi);
>                else
>                 /* Ignore small left partition. */
>                  lo = left_ptr;
> @@ -292,13 +303,13 @@ _quicksort (void *const pbase, size_t total_elems, size_t size,
>            else if ((right_ptr - lo) > (hi - left_ptr))
>              {
>               /* Push larger left partition indices. */
> -              PUSH (lo, right_ptr);
> +              top = push (top, lo, right_ptr);
>                lo = left_ptr;
>              }
>            else
>              {
>               /* Push larger right partition indices. */
> -              PUSH (left_ptr, hi);
> +              top = push (top, left_ptr, hi);
>                hi = right_ptr;
>              }
>          }
> --
> 2.34.1
>
LGTM
Reviewed-by: Noah Goldstein <goldstein.w.n@gmail.com>