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fpu/softfloat: re-factor scalbn 

This is one of the simpler manipulations you could make to a floating
point number.

Signed-off-by: Alex Bennée <alex.bennee@linaro.org>
Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
This commit is contained in:
Alex Bennée 2017-11-30 11:31:40 +00:00
parent c02e1fb80b
commit 0bfc9f1952
2 changed files with 34 additions and 73 deletions
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106
fpu/softfloat.c
View File

@ -1663,6 +1663,39 @@ float64 uint16_to_float64(uint16_t a, float_status *status)
return uint64_to_float64(a, status);
}
/* Multiply A by 2 raised to the power N. */
static FloatParts scalbn_decomposed(FloatParts a, int n, float_status *s)
{
if (unlikely(is_nan(a.cls))) {
return return_nan(a, s);
}
if (a.cls == float_class_normal) {
a.exp += n;
}
return a;
}
float16 float16_scalbn(float16 a, int n, float_status *status)
{
FloatParts pa = float16_unpack_canonical(a, status);
FloatParts pr = scalbn_decomposed(pa, n, status);
return float16_round_pack_canonical(pr, status);
}
float32 float32_scalbn(float32 a, int n, float_status *status)
{
FloatParts pa = float32_unpack_canonical(a, status);
FloatParts pr = scalbn_decomposed(pa, n, status);
return float32_round_pack_canonical(pr, status);
}
float64 float64_scalbn(float64 a, int n, float_status *status)
{
FloatParts pa = float64_unpack_canonical(a, status);
FloatParts pr = scalbn_decomposed(pa, n, status);
return float64_round_pack_canonical(pr, status);
}
/*----------------------------------------------------------------------------
| Takes a 64-bit fixed-point value `absZ' with binary point between bits 6
| and 7, and returns the properly rounded 32-bit integer corresponding to the
@ -6986,79 +7019,6 @@ MINMAX(32)
MINMAX(64)
/* Multiply A by 2 raised to the power N. */
float32 float32_scalbn(float32 a, int n, float_status *status)
{
flag aSign;
int16_t aExp;
uint32_t aSig;
a = float32_squash_input_denormal(a, status);
aSig = extractFloat32Frac( a );
aExp = extractFloat32Exp( a );
aSign = extractFloat32Sign( a );
if ( aExp == 0xFF ) {
if ( aSig ) {
return propagateFloat32NaN(a, a, status);
}
return a;
}
if (aExp != 0) {
aSig |= 0x00800000;
} else if (aSig == 0) {
return a;
} else {
aExp++;
}
if (n > 0x200) {
n = 0x200;
} else if (n < -0x200) {
n = -0x200;
}
aExp += n - 1;
aSig <<= 7;
return normalizeRoundAndPackFloat32(aSign, aExp, aSig, status);
}
float64 float64_scalbn(float64 a, int n, float_status *status)
{
flag aSign;
int16_t aExp;
uint64_t aSig;
a = float64_squash_input_denormal(a, status);
aSig = extractFloat64Frac( a );
aExp = extractFloat64Exp( a );
aSign = extractFloat64Sign( a );
if ( aExp == 0x7FF ) {
if ( aSig ) {
return propagateFloat64NaN(a, a, status);
}
return a;
}
if (aExp != 0) {
aSig |= LIT64( 0x0010000000000000 );
} else if (aSig == 0) {
return a;
} else {
aExp++;
}
if (n > 0x1000) {
n = 0x1000;
} else if (n < -0x1000) {
n = -0x1000;
}
aExp += n - 1;
aSig <<= 10;
return normalizeRoundAndPackFloat64(aSign, aExp, aSig, status);
}
floatx80 floatx80_scalbn(floatx80 a, int n, float_status *status)
{
flag aSign;

1
include/fpu/softfloat.h
View File

@ -244,6 +244,7 @@ float16 float16_sub(float16, float16, float_status *status);
float16 float16_mul(float16, float16, float_status *status);
float16 float16_muladd(float16, float16, float16, int, float_status *status);
float16 float16_div(float16, float16, float_status *status);
float16 float16_scalbn(float16, int, float_status *status);
int float16_is_quiet_nan(float16, float_status *status);
int float16_is_signaling_nan(float16, float_status *status);