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radix_trie: simplify trimkey functions

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Replacing a branch and two shifts with a single masking operation saves 64 bytes the pair of functions lookup_le and lookup_ge on amd64.  Refresh the associated comments.
Reviewed by:	alc
Differential Revision:	https://reviews.freebsd.org/D40722
This commit is contained in:
Doug Moore 2023-06-25 12:49:15 -05:00
parent 9cbc371c8a
commit a42d8fe001
2 changed files with 4 additions and 18 deletions
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11
sys/kern/subr_pctrie.c
View File

@ -156,18 +156,11 @@ pctrie_slot(uint64_t index, uint16_t level)
return ((index >> (level * PCTRIE_WIDTH)) & PCTRIE_MASK);
}
/* Trims the key after the specified level. */
/* Computes the key (index) with the low-order 'level' radix-digits zeroed. */
static __inline uint64_t
pctrie_trimkey(uint64_t index, uint16_t level)
{
uint64_t ret;
ret = index;
if (level > 0) {
ret >>= level * PCTRIE_WIDTH;
ret <<= level * PCTRIE_WIDTH;
}
return (ret);
return (index & -PCTRIE_UNITLEVEL(level));
}
/*

11
sys/vm/vm_radix.c
View File

@ -181,18 +181,11 @@ vm_radix_slot(vm_pindex_t index, uint16_t level)
return ((index >> (level * VM_RADIX_WIDTH)) & VM_RADIX_MASK);
}
/* Trims the key after the specified level. */
/* Computes the key (index) with the low-order 'level' radix-digits zeroed. */
static __inline vm_pindex_t
vm_radix_trimkey(vm_pindex_t index, uint16_t level)
{
vm_pindex_t ret;
ret = index;
if (level > 0) {
ret >>= level * VM_RADIX_WIDTH;
ret <<= level * VM_RADIX_WIDTH;
}
return (ret);
return (index & -VM_RADIX_UNITLEVEL(level));
}
/*