libgfortran/caf/shmem/allocator.c

/* Copyright (C) 2025-2026 Free Software Foundation, Inc.
   Contributed by Thomas Koenig, Nicolas Koenig, Andre Vehreschild

This file is part of the GNU Fortran Shmem Coarray Library (caf_shmem).

Caf_shmem is free software; you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation; either version 3, or (at your option)
any later version.

Caf_shmem is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
GNU General Public License for more details.

Under Section 7 of GPL version 3, you are granted additional
permissions described in the GCC Runtime Library Exception, version
3.1, as published by the Free Software Foundation.

You should have received a copy of the GNU General Public License and
a copy of the GCC Runtime Library Exception along with this program;
see the files COPYING3 and COPYING.RUNTIME respectively.  If not, see
<http://www.gnu.org/licenses/>.  */

/* Main allocation routine, works like malloc.  Round up allocations
   to the next power of two and keep free lists in buckets.  */

#ifdef HAVE_CONFIG_H
#include "config.h"
#endif

#include "libgfortran.h"

#include "allocator.h"
#include "supervisor.h"
#include "thread_support.h"

#include <assert.h>

typedef struct
{
  shared_mem_ptr next;
} bucket;

size_t
alignto (size_t size, size_t align)
{
  return align * ((size + align - 1) / align);
}

size_t pagesize;

size_t
round_to_pagesize (size_t s)
{
  return alignto (s, pagesize);
}

/* Initialize the allocator.  */

void
allocator_init (allocator *a, allocator_shared *s, shared_memory sm)
{
  *a = (allocator) {s, sm};
}

void
allocator_init_supervisor (allocator *a, allocator_shared *s, shared_memory sm)
{
  *a = (allocator) {s, sm};
  initialize_shared_mutex (&s->lock);
  for (size_t i = 0; i < VOIDP_BITS; i++)
    s->free_bucket_head[i] = SHMPTR_NULL;
}

#define MAX_ALIGN 16

static size_t
next_power_of_two (size_t size)
{
  assert (size != 1);
  return (size_t)1 << (__SIZEOF_LONG_LONG__ * __CHAR_BIT__ - __builtin_clzll (size - 1));
}

shared_mem_ptr
allocator_shared_malloc (allocator *a, size_t size)
{
  shared_mem_ptr ret;
  size_t sz;
  size_t act_size;
  int bucket_list_index;

  sz = next_power_of_two (size);
  act_size = sz > sizeof (bucket) ? sz : sizeof (bucket);
  bucket_list_index = __builtin_clzl (act_size);
  assert (bucket_list_index
	  < (int) (sizeof (a->s->free_bucket_head) / sizeof (shared_mem_ptr)));

  if (SHMPTR_IS_NULL (a->s->free_bucket_head[bucket_list_index]))
    return shared_memory_get_mem_with_alignment (a->shm, act_size, MAX_ALIGN);

  ret = a->s->free_bucket_head[bucket_list_index];
  a->s->free_bucket_head[bucket_list_index]
      = (SHMPTR_AS (bucket *, ret, a->shm)->next);
  return ret;
}

/* Free memory.  */

void
allocator_shared_free (allocator *a, shared_mem_ptr p, size_t size)
{
  bucket *b;
  size_t sz;
  int bucket_list_index;
  size_t act_size;

  sz = next_power_of_two (size);
  act_size = sz > sizeof (bucket) ? sz : sizeof (bucket);
  bucket_list_index = __builtin_clzl (act_size);

  b = SHMPTR_AS (bucket *, p, a->shm);
  b->next = a->s->free_bucket_head[bucket_list_index];
  a->s->free_bucket_head[bucket_list_index] = p;
}

void
allocator_lock (allocator *a)
{
  caf_shmem_mutex_lock (&a->s->lock);
}

void
allocator_unlock (allocator *a)
{
  caf_shmem_mutex_unlock (&a->s->lock);
}