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softfloat: Introduce sh[lr]_double primitives

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Have x86_64 assembly for them, with a fallback.
This avoids shuffling values through %cl in the x86 case.

Reviewed-by: Alex Bennée <alex.bennee@linaro.org>
Signed-off-by: Richard Henderson <richard.henderson@linaro.org>
This commit is contained in:
Richard Henderson 2020-11-09 19:08:30 -08:00
parent 5ffb6bd9c4
commit 463e45dcb4
2 changed files with 115 additions and 23 deletions
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102
fpu/softfloat.c
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@ -957,15 +957,12 @@ static int frac128_normalize(FloatParts128 *a)
{
if (a->frac_hi) {
int shl = clz64(a->frac_hi);
if (shl) {
int shr = 64 - shl;
a->frac_hi = (a->frac_hi << shl) | (a->frac_lo >> shr);
a->frac_lo = (a->frac_lo << shl);
}
a->frac_hi = shl_double(a->frac_hi, a->frac_lo, shl);
a->frac_lo <<= shl;
return shl;
} else if (a->frac_lo) {
int shl = clz64(a->frac_lo);
a->frac_hi = (a->frac_lo << shl);
a->frac_hi = a->frac_lo << shl;
a->frac_lo = 0;
return shl + 64;
}
@ -976,7 +973,7 @@ static int frac256_normalize(FloatParts256 *a)
{
uint64_t a0 = a->frac_hi, a1 = a->frac_hm;
uint64_t a2 = a->frac_lm, a3 = a->frac_lo;
int ret, shl, shr;
int ret, shl;
if (likely(a0)) {
shl = clz64(a0);
@ -1006,11 +1003,10 @@ static int frac256_normalize(FloatParts256 *a)
ret += shl;
}
shr = -shl & 63;
a0 = (a0 << shl) | (a1 >> shr);
a1 = (a1 << shl) | (a2 >> shr);
a2 = (a2 << shl) | (a3 >> shr);
a3 = (a3 << shl);
a0 = shl_double(a0, a1, shl);
a1 = shl_double(a1, a2, shl);
a2 = shl_double(a2, a3, shl);
a3 <<= shl;
done:
a->frac_hi = a0;
@ -1029,7 +1025,20 @@ static void frac64_shl(FloatParts64 *a, int c)
static void frac128_shl(FloatParts128 *a, int c)
{
shift128Left(a->frac_hi, a->frac_lo, c, &a->frac_hi, &a->frac_lo);
uint64_t a0 = a->frac_hi, a1 = a->frac_lo;
if (c & 64) {
a0 = a1, a1 = 0;
}
c &= 63;
if (c) {
a0 = shl_double(a0, a1, c);
a1 = a1 << c;
}
a->frac_hi = a0;
a->frac_lo = a1;
}
#define frac_shl(A, C) FRAC_GENERIC_64_128(shl, A)(A, C)
@ -1041,19 +1050,68 @@ static void frac64_shr(FloatParts64 *a, int c)
static void frac128_shr(FloatParts128 *a, int c)
{
shift128Right(a->frac_hi, a->frac_lo, c, &a->frac_hi, &a->frac_lo);
uint64_t a0 = a->frac_hi, a1 = a->frac_lo;
if (c & 64) {
a1 = a0, a0 = 0;
}
c &= 63;
if (c) {
a1 = shr_double(a0, a1, c);
a0 = a0 >> c;
}
a->frac_hi = a0;
a->frac_lo = a1;
}
#define frac_shr(A, C) FRAC_GENERIC_64_128(shr, A)(A, C)
static void frac64_shrjam(FloatParts64 *a, int c)
{
shift64RightJamming(a->frac, c, &a->frac);
uint64_t a0 = a->frac;
if (likely(c != 0)) {
if (likely(c < 64)) {
a0 = (a0 >> c) | (shr_double(a0, 0, c) != 0);
} else {
a0 = a0 != 0;
}
a->frac = a0;
}
}
static void frac128_shrjam(FloatParts128 *a, int c)
{
shift128RightJamming(a->frac_hi, a->frac_lo, c, &a->frac_hi, &a->frac_lo);
uint64_t a0 = a->frac_hi, a1 = a->frac_lo;
uint64_t sticky = 0;
if (unlikely(c == 0)) {
return;
} else if (likely(c < 64)) {
/* nothing */
} else if (likely(c < 128)) {
sticky = a1;
a1 = a0;
a0 = 0;
c &= 63;
if (c == 0) {
goto done;
}
} else {
sticky = a0 | a1;
a0 = a1 = 0;
goto done;
}
sticky |= shr_double(a1, 0, c);
a1 = shr_double(a0, a1, c);
a0 = a0 >> c;
done:
a->frac_lo = a1 | (sticky != 0);
a->frac_hi = a0;
}
static void frac256_shrjam(FloatParts256 *a, int c)
@ -1061,7 +1119,6 @@ static void frac256_shrjam(FloatParts256 *a, int c)
uint64_t a0 = a->frac_hi, a1 = a->frac_hm;
uint64_t a2 = a->frac_lm, a3 = a->frac_lo;
uint64_t sticky = 0;
int invc;
if (unlikely(c == 0)) {
return;
@ -1086,12 +1143,11 @@ static void frac256_shrjam(FloatParts256 *a, int c)
goto done;
}
invc = -c & 63;
sticky |= a3 << invc;
a3 = (a3 >> c) | (a2 << invc);
a2 = (a2 >> c) | (a1 << invc);
a1 = (a1 >> c) | (a0 << invc);
a0 = (a0 >> c);
sticky |= shr_double(a3, 0, c);
a3 = shr_double(a2, a3, c);
a2 = shr_double(a1, a2, c);
a1 = shr_double(a0, a1, c);
a0 = a0 >> c;
done:
a->frac_lo = a3 | (sticky != 0);