Handle GMP allocations through libgc and remove bignum finalizers.

This significantly speeds up loads that create lots of bignums, like
(language cps slot-allocation) for files with many top-level
definitions.  Compiling such a file is typically 2.5 times faster.

See <https://lists.gnu.org/archive/html/guile-devel/2020-02/msg00023.html>.

* libguile/numbers.c (custom_gmp_malloc): Use
'scm_gc_malloc_pointerless' instead of 'scm_malloc'.
(custom_gmp_realloc): Use 'scm_gc_realloc'.
(custom_gmp_free): Remove call to 'free'.
(make_bignum): Use 'scm_gc_malloc' instead of 'scm_gc_malloc_pointerless'.
Call 'scm_i_set_finalizer' only when SCM_INSTALL_GMP_MEMORY_FUNCTIONS is
false.

1 files changed, 12 insertions, 7 deletions

diff --git a/libguile/numbers.c b/libguile/numbers.c
index d1b463358..19d2b2d87 100644
--- a/libguile/numbers.c
+++ b/libguile/numbers.c
@@ -1,4 +1,4 @@
-/* Copyright 1995-2016,2018-2019
+/* Copyright 1995-2016,2018-2020
      Free Software Foundation, Inc.
 
    Portions Copyright 1990-1993 by AT&T Bell Laboratories and Bellcore.
@@ -237,19 +237,20 @@ finalize_bignum (void *ptr, void *data)
 static void *
 custom_gmp_malloc (size_t alloc_size)
 {
-  return scm_malloc (alloc_size);
+  return scm_gc_malloc_pointerless (alloc_size, "GMP");
 }
 
 static void *
 custom_gmp_realloc (void *old_ptr, size_t old_size, size_t new_size)
 {
-  return scm_realloc (old_ptr, new_size);
+  return scm_gc_realloc (old_ptr, old_size, new_size, "GMP");
 }
 
 static void
 custom_gmp_free (void *ptr, size_t size)
 {
-  free (ptr);
+  /* Do nothing: all memory allocated by GMP is under GC control and
+     will be freed when needed.  */
 }
 
 
@@ -260,11 +261,15 @@ make_bignum (void)
   scm_t_bits *p;
 
   /* Allocate one word for the type tag and enough room for an `mpz_t'.  */
-  p = scm_gc_malloc_pointerless (sizeof (scm_t_bits) + sizeof (mpz_t),
-				 "bignum");
+  p = scm_gc_malloc (sizeof (scm_t_bits) + sizeof (mpz_t),
+                     "bignum");
   p[0] = scm_tc16_big;
 
-  scm_i_set_finalizer (p, finalize_bignum, NULL);
+  /* When the 'custom_gmp_*' functions are in use, no need to set a
+     finalizer since allocated memory is under GC control.  In other
+     cases, set a finalizer to call 'mpz_clear', which is expensive.  */
+  if (!scm_install_gmp_memory_functions)
+    scm_i_set_finalizer (p, finalize_bignum, NULL);
 
   return SCM_PACK (p);
 }