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ARM: Speed up __mesabi_uldiv for powers-of-two divisors.

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* lib/mes/div.c (__mesabi_uldiv): Speed up division for powers-of-two
divisors.
This commit is contained in:
Danny Milosavljevic 2020-11-15 14:36:10 +01:00 committed by Jan (janneke) Nieuwenhuizen
parent bfd6792d07
commit 10bcb3709b
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GPG key ID: F3C1A0D9C1D65273
1 changed files with 25 additions and 3 deletions
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28
lib/mes/div.c
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@ -50,11 +50,32 @@ __mesabi_uldiv (unsigned long a, unsigned long b, unsigned long* remainder)
if (!remainder) if (!remainder)
remainder = &tmp; remainder = &tmp;
*remainder = 0; *remainder = 0;
if (b == 1) switch (b) {
case 64UL:
*remainder = a & 63UL;
return a >> 6UL;
case 32UL:
*remainder = a & 31UL;
return a >> 5UL;
case 16UL:
*remainder = a & 15UL;
return a >> 4UL;
case 8UL:
*remainder = a & 7UL;
return a >> 3UL;
case 4UL:
*remainder = a & 3UL;
return a >> 2UL;
case 2UL:
*remainder = a & 1UL;
return a >> 1UL;
case 1UL:
*remainder = 0;
return a; return a;
else if (b == 0) case 0UL:
__mesabi_div0(); __mesabi_div0();
else return 0UL;
default:
{ {
unsigned long x; unsigned long x;
for (x = 0; a >= b; a -= b) for (x = 0; a >= b; a -= b)
@ -62,6 +83,7 @@ __mesabi_uldiv (unsigned long a, unsigned long b, unsigned long* remainder)
*remainder = a; *remainder = a;
return x; return x;
} }
}
} }
/* Note: Rounds towards zero. /* Note: Rounds towards zero.