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target-alpha: Special case cmpbge with zero 

Knowing the comparator is zero leads to a simpler operation.

Signed-off-by: Richard Henderson <rth@twiddle.net>
This commit is contained in:
Richard Henderson 2015-08-05 11:04:11 -07:00
parent 5f2a80adc6
commit 112e4518f0
3 changed files with 21 additions and 1 deletions
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1
target-alpha/helper.h
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@ -10,6 +10,7 @@ DEF_HELPER_FLAGS_1(cttz, TCG_CALL_NO_RWG_SE, i64, i64)
DEF_HELPER_FLAGS_2(zap, TCG_CALL_NO_RWG_SE, i64, i64, i64)
DEF_HELPER_FLAGS_2(zapnot, TCG_CALL_NO_RWG_SE, i64, i64, i64)
DEF_HELPER_FLAGS_1(cmpbe0, TCG_CALL_NO_RWG_SE, i64, i64)
DEF_HELPER_FLAGS_2(cmpbge, TCG_CALL_NO_RWG_SE, i64, i64, i64)
DEF_HELPER_FLAGS_2(minub8, TCG_CALL_NO_RWG_SE, i64, i64, i64)

14
target-alpha/int_helper.c
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@ -58,6 +58,20 @@ uint64_t helper_zap(uint64_t val, uint64_t mask)
return helper_zapnot(val, ~mask);
}
uint64_t helper_cmpbe0(uint64_t a)
{
uint64_t m = 0x7f7f7f7f7f7f7f7fULL;
uint64_t c = ~(((a & m) + m) | a | m);
/* a.......b.......c.......d.......e.......f.......g.......h....... */
c |= c << 7;
/* ab......bc......cd......de......ef......fg......gh......h....... */
c |= c << 14;
/* abcd....bcde....cdef....defg....efgh....fgh.....gh......h....... */
c |= c << 28;
/* abcdefghbcdefgh.cdefgh..defgh...efgh....fgh.....gh......h....... */
return c >> 56;
}
uint64_t helper_cmpbge(uint64_t a, uint64_t b)
{
uint64_t mask = 0x00ff00ff00ff00ffULL;

7
target-alpha/translate.c
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@ -1507,7 +1507,12 @@ static ExitStatus translate_one(DisasContext *ctx, uint32_t insn)
break;
case 0x0F:
/* CMPBGE */
gen_helper_cmpbge(vc, va, vb);
if (ra == 31) {
/* Special case 0 >= X as X == 0. */
gen_helper_cmpbe0(vc, vb);
} else {
gen_helper_cmpbge(vc, va, vb);
}
break;
case 0x12:
/* S8ADDL */