david.venhoff/QEMU-Nyx-fork
1
0
Fork 0
Code Issues Pull Requests Actions Packages Projects Releases Wiki Activity

target-alpha: Rewrite helper_cmpbge using bit tests

Browse Source 
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
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

37
target-alpha/int_helper.c
View File

@ -58,20 +58,33 @@ uint64_t helper_zap(uint64_t val, uint64_t mask)
return helper_zapnot(val, ~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; uint64_t mask = 0x00ff00ff00ff00ffULL;
int i; uint64_t test = 0x0100010001000100ULL;
uint64_t al, ah, bl, bh, cl, ch;
res = 0; /* Separate the bytes to avoid false positives. */
for (i = 0; i < 8; i++) { al = a & mask;
opa = op1 >> (i * 8); bl = b & mask;
opb = op2 >> (i * 8); ah = (a >> 8) & mask;
if (opa >= opb) { bh = (b >> 8) & mask;
res |= 1 << i;
} /* "Compare". If a byte in B is greater than a byte in A,
} it will clear the test bit. */
return res; 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) uint64_t helper_minub8(uint64_t op1, uint64_t op2)