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pointer-set.c (hash1): Use integer part of 2^64 / phi instead 2^32 / phi if long is 64-bit.

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* pointer-set.c (hash1): Use integer part of 2^64 / phi
	instead 2^32 / phi if long is 64-bit.

From-SVN: r89165
This commit is contained in:
Jakub Jelinek 2004-10-17 09:15:53 +02:00 committed by Jakub Jelinek
parent 9596e0648d
commit bc54ef99a2
2 changed files with 16 additions and 3 deletions
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5
gcc/ChangeLog
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@ -1,3 +1,8 @@
2004-10-17 Jakub Jelinek <jakub@redhat.com>
* pointer-set.c (hash1): Use integer part of 2^64 / phi
instead 2^32 / phi if long is 64-bit.
2004-10-17 Joseph S. Myers <jsm@polyomino.org.uk>
* c-common.h (enum rid): Remove RID_PTRBASE, RID_PTREXTENT and

14
gcc/pointer-set.c
View File

@ -46,8 +46,8 @@ struct pointer_set_t
relatively prime to 2^sizeof(size_t). The result is two words.
Discard the most significant word, and return the most significant
N bits of the least significant word. As suggested by Knuth, our
choice for A is the integer part of 2^32 / phi, where phi is the
golden ratio.
choice for A is the integer part of (ULONG_MAX + 1.0) / phi, where phi
is the golden ratio.
We don't need to do anything special for full-width multiplication
because we're only interested in the least significant word of the
@ -56,8 +56,16 @@ struct pointer_set_t
static inline size_t
hash1 (const void *p, unsigned long max, unsigned long logmax)
{
#if HOST_BITS_PER_LONG == 32
const unsigned long A = 0x9e3779b9u;
const unsigned long shift = sizeof(unsigned long) * CHAR_BIT - logmax;
#elif HOST_BITS_PER_LONG == 64
const unsigned long A = 0x9e3779b97f4a7c16ul;
#else
const double M = (ULONG_MAX + 1.0);
const double B = M / ((sqrt (5) - 1) / 2.0);
const unsigned long A = B - (floor (B / M) * M);
#endif
const unsigned long shift = sizeof (unsigned long) * CHAR_BIT - logmax;
return ((A * (unsigned long) p) >> shift) & (max - 1);
}