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*From*: DJ Delorie <dj at redhat dot com>*To*: binutils at sources dot redhat dot com*Date*: Mon, 1 May 2006 15:37:40 -0400*Subject*: [patch] expanding tables for bfd/hash.c

I originally proposed this patch nearly two years ago, but only recently got access to a testcase that proved it fixed what I originall wrote it for (in this case, a 1.5Gb executable went from 65 minutes of CPU time to 45 seconds!) I've tested this for regressions with a mips64-elf GCC test run, and I'm finally committing it. PS: anyone who wants to volunteer to replace bfd's has with libiberty's hash may do so by saying "why aren't we using libiberty's hash functions?" ;-) 2006-05-01 DJ Delorie <dj@redhat.com> * bfd-in.h (bfd_hash_table): Add count field. * bfd-in2.h: Regenerate. * hash.c (higher_prime_number): New. (bfd_hash_table_inint_n): Init count field. (bfd_hash_lookup): Grow table as needed. Index: bfd-in.h =================================================================== RCS file: /cvs/src/src/bfd/bfd-in.h,v retrieving revision 1.113 diff -p -U3 -r1.113 bfd-in.h --- bfd-in.h 16 Mar 2006 12:20:15 -0000 1.113 +++ bfd-in.h 1 May 2006 19:32:05 -0000 @@ -376,6 +376,8 @@ struct bfd_hash_table struct bfd_hash_entry **table; /* The number of slots in the hash table. */ unsigned int size; + /* The number of entries in the hash table. */ + unsigned int count; /* The size of elements. */ unsigned int entsize; /* A function used to create new elements in the hash table. The Index: bfd-in2.h =================================================================== RCS file: /cvs/src/src/bfd/bfd-in2.h,v retrieving revision 1.387 diff -p -U3 -r1.387 bfd-in2.h --- bfd-in2.h 26 Mar 2006 00:38:42 -0000 1.387 +++ bfd-in2.h 1 May 2006 19:32:06 -0000 @@ -383,6 +383,8 @@ struct bfd_hash_table struct bfd_hash_entry **table; /* The number of slots in the hash table. */ unsigned int size; + /* The number of entries in the hash table. */ + unsigned int count; /* The size of elements. */ unsigned int entsize; /* A function used to create new elements in the hash table. The Index: hash.c =================================================================== RCS file: /cvs/src/src/bfd/hash.c,v retrieving revision 1.20 diff -p -U3 -r1.20 hash.c --- hash.c 16 Mar 2006 12:20:15 -0000 1.20 +++ hash.c 1 May 2006 19:32:06 -0000 @@ -298,7 +298,72 @@ SUBSUBSECTION */ /* The default number of entries to use when creating a hash table. */ -#define DEFAULT_SIZE 4051 +#define DEFAULT_SIZE (4093) + +/* The following function returns a nearest prime number which is + greater than N, and near a power of two. Copied from libiberty. */ + +static unsigned long +higher_prime_number (unsigned long n) +{ + /* These are primes that are near, but slightly smaller than, a + power of two. */ + static const unsigned long primes[] = { + (unsigned long) 7, + (unsigned long) 13, + (unsigned long) 31, + (unsigned long) 61, + (unsigned long) 127, + (unsigned long) 251, + (unsigned long) 509, + (unsigned long) 1021, + (unsigned long) 2039, + (unsigned long) 4093, + (unsigned long) 8191, + (unsigned long) 16381, + (unsigned long) 32749, + (unsigned long) 65521, + (unsigned long) 131071, + (unsigned long) 262139, + (unsigned long) 524287, + (unsigned long) 1048573, + (unsigned long) 2097143, + (unsigned long) 4194301, + (unsigned long) 8388593, + (unsigned long) 16777213, + (unsigned long) 33554393, + (unsigned long) 67108859, + (unsigned long) 134217689, + (unsigned long) 268435399, + (unsigned long) 536870909, + (unsigned long) 1073741789, + (unsigned long) 2147483647, + /* 4294967291L */ + ((unsigned long) 2147483647) + ((unsigned long) 2147483644), + }; + + const unsigned long *low = &primes[0]; + const unsigned long *high = &primes[sizeof(primes) / sizeof(primes[0])]; + + while (low != high) + { + const unsigned long *mid = low + (high - low) / 2; + if (n >= *mid) + low = mid + 1; + else + high = mid; + } + + /* If we've run out of primes, abort. */ + if (n > *low) + { + fprintf (stderr, "Cannot find prime bigger than %lu\n", n); + abort (); + } + + return *low; +} + static size_t bfd_default_hash_table_size = DEFAULT_SIZE; /* Create a new hash table, given a number of entries. */ @@ -330,6 +395,7 @@ bfd_hash_table_init_n (struct bfd_hash_t memset ((void *) table->table, 0, alloc); table->size = size; table->entsize = entsize; + table->count = 0; table->newfunc = newfunc; return TRUE; } @@ -402,6 +468,7 @@ bfd_hash_lookup (struct bfd_hash_table * if (copy) { char *new; + table->count ++; new = objalloc_alloc ((struct objalloc *) table->memory, len + 1); if (!new) @@ -417,6 +484,38 @@ bfd_hash_lookup (struct bfd_hash_table * hashp->next = table->table[index]; table->table[index] = hashp; + if (table->count > table->size * 3 / 4) + { + int newsize = higher_prime_number (table->size); + struct bfd_hash_entry **newtable; + unsigned int hi; + unsigned int alloc; + + alloc = newsize * sizeof (struct bfd_hash_entry *); + + newtable = ((struct bfd_hash_entry **) + objalloc_alloc ((struct objalloc *) table->memory, alloc)); + memset ((PTR) newtable, 0, alloc); + + for (hi = 0; hi < table->size; hi ++) + while (table->table[hi]) + { + struct bfd_hash_entry *chain = table->table[hi]; + struct bfd_hash_entry *chain_end = chain; + int index; + + while (chain_end->next && chain_end->next->hash == chain->hash) + chain_end = chain_end->next; + + table->table[hi] = chain_end->next; + index = chain->hash % newsize; + chain_end->next = newtable[index]; + newtable[index] = chain; + } + table->table = newtable; + table->size = newsize; + } + return hashp; }

**Follow-Ups**:**Re: [patch] expanding tables for bfd/hash.c***From:*H. J. Lu

**Re: [patch] expanding tables for bfd/hash.c***From:*Alan Modra

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