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target-alpha: Rewrite helper_cmpbge using bit tests 

Not quite as good as using a proper host vector compare,
but certainly better than a loop.

Signed-off-by: Richard Henderson <rth@twiddle.net>
This commit is contained in:
Richard Henderson 2015-08-05 10:33:12 -07:00
parent 074a9925e1
commit 5f2a80adc6
1 changed files with 25 additions and 12 deletions
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37
target-alpha/int_helper.c
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@ -58,20 +58,33 @@ uint64_t helper_zap(uint64_t val, uint64_t mask)
return helper_zapnot(val, ~mask);
}
uint64_t helper_cmpbge(uint64_t op1, uint64_t op2)
uint64_t helper_cmpbge(uint64_t a, uint64_t b)
{
uint8_t opa, opb, res;
int i;
uint64_t mask = 0x00ff00ff00ff00ffULL;
uint64_t test = 0x0100010001000100ULL;
uint64_t al, ah, bl, bh, cl, ch;
res = 0;
for (i = 0; i < 8; i++) {
opa = op1 >> (i * 8);
opb = op2 >> (i * 8);
if (opa >= opb) {
res |= 1 << i;
}
}
return res;
/* Separate the bytes to avoid false positives. */
al = a & mask;
bl = b & mask;
ah = (a >> 8) & mask;
bh = (b >> 8) & mask;
/* "Compare". If a byte in B is greater than a byte in A,
it will clear the test bit. */
cl = ((al | test) - bl) & test;
ch = ((ah | test) - bh) & test;
/* Fold all of the test bits into a contiguous set. */
/* ch=.......a...............c...............e...............g........ */
/* cl=.......b...............d...............f...............h........ */
cl += ch << 1;
/* cl=......ab..............cd..............ef..............gh........ */
cl |= cl << 14;
/* cl=......abcd............cdef............efgh............gh........ */
cl |= cl << 28;
/* cl=......abcdefgh........cdefgh..........efgh............gh........ */
return cl >> 50;
}
uint64_t helper_minub8(uint64_t op1, uint64_t op2)