Skip to content

Commit

Permalink
softfloat: merge floatx80_mod and floatx80_rem
Browse files Browse the repository at this point in the history 
The m68k-specific softfloat code includes a function floatx80_mod that
is extremely similar to floatx80_rem, but computing the remainder
based on truncating the quotient toward zero rather than rounding it
to nearest integer.  This is also useful for emulating the x87 fprem
and fprem1 instructions.  Change the floatx80_rem implementation into
floatx80_modrem that can perform either operation, with both
floatx80_rem and floatx80_mod as thin wrappers available for all
targets.

There does not appear to be any use for the _mod operation for other
floating-point formats in QEMU (the only other architectures using
_rem at all are linux-user/arm/nwfpe, for FPA emulation, and openrisc,
for instructions that have been removed in the latest version of the
architecture), so no change is made to the code for other formats.

Signed-off-by: Joseph Myers <joseph@codesourcery.com>
Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
Message-Id: <alpine.DEB.2.21.2006081654280.23637@digraph.polyomino.org.uk>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
  • Loading branch information
@jsm28 @bonzini
jsm28 authored and bonzini committed Jun 26, 2020
1 parent eca3064 commit 6b8b013
Show file tree
Hide file tree
Showing 4 changed files with 40 additions and 95 deletions.
49 changes: 38 additions & 11 deletions fpu/softfloat.c
View file
Original file line number Diff line number Diff line change
Expand Up @@ -5697,10 +5697,13 @@ floatx80 floatx80_div(floatx80 a, floatx80 b, float_status *status)
/*----------------------------------------------------------------------------
| Returns the remainder of the extended double-precision floating-point value
| `a' with respect to the corresponding value `b'. The operation is performed
| according to the IEC/IEEE Standard for Binary Floating-Point Arithmetic.
| according to the IEC/IEEE Standard for Binary Floating-Point Arithmetic,
| if 'mod' is false; if 'mod' is true, return the remainder based on truncating
| the quotient toward zero instead.
*----------------------------------------------------------------------------*/

floatx80 floatx80_rem(floatx80 a, floatx80 b, float_status *status)
floatx80 floatx80_modrem(floatx80 a, floatx80 b, bool mod,
float_status *status)
{
bool aSign, zSign;
int32_t aExp, bExp, expDiff;
Expand Down Expand Up @@ -5746,7 +5749,7 @@ floatx80 floatx80_rem(floatx80 a, floatx80 b, float_status *status)
expDiff = aExp - bExp;
aSig1 = 0;
if ( expDiff < 0 ) {
if ( expDiff < -1 ) return a;
if ( mod || expDiff < -1 ) return a;
shift128Right( aSig0, 0, 1, &aSig0, &aSig1 );
expDiff = 0;
}
Expand Down Expand Up @@ -5778,21 +5781,45 @@ floatx80 floatx80_rem(floatx80 a, floatx80 b, float_status *status)
term1 = 0;
term0 = bSig;
}
sub128( term0, term1, aSig0, aSig1, &alternateASig0, &alternateASig1 );
if ( lt128( alternateASig0, alternateASig1, aSig0, aSig1 )
|| ( eq128( alternateASig0, alternateASig1, aSig0, aSig1 )
&& ( q & 1 ) )
) {
aSig0 = alternateASig0;
aSig1 = alternateASig1;
zSign = ! zSign;
if (!mod) {
sub128( term0, term1, aSig0, aSig1, &alternateASig0, &alternateASig1 );
if ( lt128( alternateASig0, alternateASig1, aSig0, aSig1 )
|| ( eq128( alternateASig0, alternateASig1, aSig0, aSig1 )
&& ( q & 1 ) )
) {
aSig0 = alternateASig0;
aSig1 = alternateASig1;
zSign = ! zSign;
}
}
return
normalizeRoundAndPackFloatx80(
80, zSign, bExp + expDiff, aSig0, aSig1, status);

}

/*----------------------------------------------------------------------------
| Returns the remainder of the extended double-precision floating-point value
| `a' with respect to the corresponding value `b'. The operation is performed
| according to the IEC/IEEE Standard for Binary Floating-Point Arithmetic.
*----------------------------------------------------------------------------*/

floatx80 floatx80_rem(floatx80 a, floatx80 b, float_status *status)
{
return floatx80_modrem(a, b, false, status);
}

/*----------------------------------------------------------------------------
| Returns the remainder of the extended double-precision floating-point value
| `a' with respect to the corresponding value `b', with the quotient truncated
| toward zero.
*----------------------------------------------------------------------------*/

floatx80 floatx80_mod(floatx80 a, floatx80 b, float_status *status)
{
return floatx80_modrem(a, b, true, status);
}

/*----------------------------------------------------------------------------
| Returns the square root of the extended double-precision floating-point
| value `a'. The operation is performed according to the IEC/IEEE Standard
Expand Down
2 changes: 2 additions & 0 deletions include/fpu/softfloat.h
View file
Original file line number Diff line number Diff line change
Expand Up @@ -687,6 +687,8 @@ floatx80 floatx80_add(floatx80, floatx80, float_status *status);
floatx80 floatx80_sub(floatx80, floatx80, float_status *status);
floatx80 floatx80_mul(floatx80, floatx80, float_status *status);
floatx80 floatx80_div(floatx80, floatx80, float_status *status);
floatx80 floatx80_modrem(floatx80, floatx80, bool, float_status *status);
floatx80 floatx80_mod(floatx80, floatx80, float_status *status);
floatx80 floatx80_rem(floatx80, floatx80, float_status *status);
floatx80 floatx80_sqrt(floatx80, float_status *status);
FloatRelation floatx80_compare(floatx80, floatx80, float_status *status);
Expand Down
83 changes: 0 additions & 83 deletions target/m68k/softfloat.c
View file
Original file line number Diff line number Diff line change
Expand Up @@ -42,89 +42,6 @@ static floatx80 propagateFloatx80NaNOneArg(floatx80 a, float_status *status)
return a;
}

/*
* Returns the modulo remainder of the extended double-precision floating-point
* value `a' with respect to the corresponding value `b'.
*/

floatx80 floatx80_mod(floatx80 a, floatx80 b, float_status *status)
{
bool aSign, zSign;
int32_t aExp, bExp, expDiff;
uint64_t aSig0, aSig1, bSig;
uint64_t qTemp, term0, term1;

aSig0 = extractFloatx80Frac(a);
aExp = extractFloatx80Exp(a);
aSign = extractFloatx80Sign(a);
bSig = extractFloatx80Frac(b);
bExp = extractFloatx80Exp(b);

if (aExp == 0x7FFF) {
if ((uint64_t) (aSig0 << 1)
|| ((bExp == 0x7FFF) && (uint64_t) (bSig << 1))) {
return propagateFloatx80NaN(a, b, status);
}
goto invalid;
}
if (bExp == 0x7FFF) {
if ((uint64_t) (bSig << 1)) {
return propagateFloatx80NaN(a, b, status);
}
return a;
}
if (bExp == 0) {
if (bSig == 0) {
invalid:
float_raise(float_flag_invalid, status);
return floatx80_default_nan(status);
}
normalizeFloatx80Subnormal(bSig, &bExp, &bSig);
}
if (aExp == 0) {
if ((uint64_t) (aSig0 << 1) == 0) {
return a;
}
normalizeFloatx80Subnormal(aSig0, &aExp, &aSig0);
}
bSig |= UINT64_C(0x8000000000000000);
zSign = aSign;
expDiff = aExp - bExp;
aSig1 = 0;
if (expDiff < 0) {
return a;
}
qTemp = (bSig <= aSig0);
if (qTemp) {
aSig0 -= bSig;
}
expDiff -= 64;
while (0 < expDiff) {
qTemp = estimateDiv128To64(aSig0, aSig1, bSig);
qTemp = (2 < qTemp) ? qTemp - 2 : 0;
mul64To128(bSig, qTemp, &term0, &term1);
sub128(aSig0, aSig1, term0, term1, &aSig0, &aSig1);
shortShift128Left(aSig0, aSig1, 62, &aSig0, &aSig1);
expDiff -= 62;
}
expDiff += 64;
if (0 < expDiff) {
qTemp = estimateDiv128To64(aSig0, aSig1, bSig);
qTemp = (2 < qTemp) ? qTemp - 2 : 0;
qTemp >>= 64 - expDiff;
mul64To128(bSig, qTemp << (64 - expDiff), &term0, &term1);
sub128(aSig0, aSig1, term0, term1, &aSig0, &aSig1);
shortShift128Left(0, bSig, 64 - expDiff, &term0, &term1);
while (le128(term0, term1, aSig0, aSig1)) {
++qTemp;
sub128(aSig0, aSig1, term0, term1, &aSig0, &aSig1);
}
}
return
normalizeRoundAndPackFloatx80(
80, zSign, bExp + expDiff, aSig0, aSig1, status);
}

/*
* Returns the mantissa of the extended double-precision floating-point
* value `a'.
Expand Down
1 change: 0 additions & 1 deletion target/m68k/softfloat.h
View file
Original file line number Diff line number Diff line change
Expand Up @@ -23,7 +23,6 @@
#define TARGET_M68K_SOFTFLOAT_H
#include "fpu/softfloat.h"

floatx80 floatx80_mod(floatx80 a, floatx80 b, float_status *status);
floatx80 floatx80_getman(floatx80 a, float_status *status);
floatx80 floatx80_getexp(floatx80 a, float_status *status);
floatx80 floatx80_scale(floatx80 a, floatx80 b, float_status *status);
Expand Down

0 comments on commit 6b8b013

Please sign in to comment.