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implement unsigned -> float casts

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amd64 lacks an instruction for this so it has to be implemented with
signed -> float casts:
 - Word casting is done by zero-extending the word to a long and then doing
   a regular signed cast.
 - Long casting is done by dividing by two with correct rounding if the
   highest bit is set and casting that to float, then adding
   1 to mantissa with integer addition
This commit is contained in:
Bor Grošelj Simić 2022-01-28 02:06:17 +01:00 • committed by Quentin Carbonneaux
parent b0d27d8a01
commit 74d022f975
6 changed files with 107 additions and 5 deletions
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45
amd64/isel.c
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@ -201,8 +201,8 @@ selcmp(Ref arg[2], int k, int swap, Fn *fn)
static void
sel(Ins i, ANum *an, Fn *fn)
{
Ref r0, r1;
int x, k, kc, swap;
Ref r0, r1, tmp[7];
int x, j, k, kc, swap;
int64_t sz;
Ins *i0, *i1;
@ -266,6 +266,47 @@ sel(Ins i, ANum *an, Fn *fn)
emit(Ocopy, Kw, TMP(RCX), r0, R);
fixarg(&i1->arg[0], argcls(&i, 0), i1, fn);
break;
case Ouwtof:
r0 = newtmp("utof", Kl, fn);
emit(Osltof, k, i.to, r0, R);
emit(Oextuw, Kl, r0, i.arg[0], R);
fixarg(&curi->arg[0], k, curi, fn);
break;
case Oultof:
/*
%mask =l and %arg.0, 1
%isbig =l shr %arg.0, 63
%divided =l shr %arg.0, %isbig
%or =l or %mask, %divided
%float =d sltof %or
%cast =l cast %float
%addend =l shl %isbig, 52
%sum =l add %cast, %addend
%result =d cast %sum
*/
r0 = newtmp("utof", k, fn);
if (k == Ks)
kc = Kw;
else
kc = Kl;
for (j=0; j<4; j++)
tmp[j] = newtmp("utof", Kl, fn);
for (; j<7; j++)
tmp[j] = newtmp("utof", kc, fn);
emit(Ocast, k, i.to, tmp[6], R);
emit(Oadd, kc, tmp[6], tmp[4], tmp[5]);
emit(Oshl, kc, tmp[5], tmp[1], getcon(k == Ks ? 23 : 52, fn));
emit(Ocast, kc, tmp[4], r0, R);
emit(Osltof, k, r0, tmp[3], R);
emit(Oor, Kl, tmp[3], tmp[0], tmp[2]);
emit(Oshr, Kl, tmp[2], i.arg[0], tmp[1]);
sel(*curi++, an, fn);
emit(Oshr, Kl, tmp[1], i.arg[0], getcon(63, fn));
fixarg(&curi->arg[0], Kl, curi, fn);
emit(Oand, Kl, tmp[0], i.arg[0], getcon(1, fn));
fixarg(&curi->arg[0], Kl, curi, fn);
break;
case Onop:
break;
case Ostored: