softfloat: Refactor code handling various rounding modes

Refactor the code in various functions which calculates rounding
increments given the current rounding mode, so that instead of a
set of nested if statements we have a simple switch statement.
This will give us a clean place to add the case for the new
tiesAway rounding mode.

Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
Reviewed-by: Richard Henderson <rth@twiddle.net>
This commit is contained in:
Peter Maydell 2014-01-07 17:19:12 +00:00
parent 7b378119bd
commit 01a0b83cdb
1 changed files with 241 additions and 164 deletions

View File

@ -42,6 +42,9 @@ these four paragraphs for those parts of this code that are retained.
#include "fpu/softfloat.h" #include "fpu/softfloat.h"
/* We only need stdlib for abort() */
#include <stdlib.h>
/*---------------------------------------------------------------------------- /*----------------------------------------------------------------------------
| Primitive arithmetic functions, including multi-word arithmetic, and | Primitive arithmetic functions, including multi-word arithmetic, and
| division and square root approximations. (Can be specialized to target if | division and square root approximations. (Can be specialized to target if
@ -106,20 +109,21 @@ static int32 roundAndPackInt32( flag zSign, uint64_t absZ STATUS_PARAM)
roundingMode = STATUS(float_rounding_mode); roundingMode = STATUS(float_rounding_mode);
roundNearestEven = ( roundingMode == float_round_nearest_even ); roundNearestEven = ( roundingMode == float_round_nearest_even );
switch (roundingMode) {
case float_round_nearest_even:
roundIncrement = 0x40; roundIncrement = 0x40;
if ( ! roundNearestEven ) { break;
if ( roundingMode == float_round_to_zero ) { case float_round_to_zero:
roundIncrement = 0; roundIncrement = 0;
} break;
else { case float_round_up:
roundIncrement = 0x7F; roundIncrement = zSign ? 0 : 0x7f;
if ( zSign ) { break;
if ( roundingMode == float_round_up ) roundIncrement = 0; case float_round_down:
} roundIncrement = zSign ? 0x7f : 0;
else { break;
if ( roundingMode == float_round_down ) roundIncrement = 0; default:
} abort();
}
} }
roundBits = absZ & 0x7F; roundBits = absZ & 0x7F;
absZ = ( absZ + roundIncrement )>>7; absZ = ( absZ + roundIncrement )>>7;
@ -155,19 +159,21 @@ static int64 roundAndPackInt64( flag zSign, uint64_t absZ0, uint64_t absZ1 STATU
roundingMode = STATUS(float_rounding_mode); roundingMode = STATUS(float_rounding_mode);
roundNearestEven = ( roundingMode == float_round_nearest_even ); roundNearestEven = ( roundingMode == float_round_nearest_even );
switch (roundingMode) {
case float_round_nearest_even:
increment = ((int64_t) absZ1 < 0); increment = ((int64_t) absZ1 < 0);
if ( ! roundNearestEven ) { break;
if ( roundingMode == float_round_to_zero ) { case float_round_to_zero:
increment = 0; increment = 0;
} break;
else { case float_round_up:
if ( zSign ) { increment = !zSign && absZ1;
increment = ( roundingMode == float_round_down ) && absZ1; break;
} case float_round_down:
else { increment = zSign && absZ1;
increment = ( roundingMode == float_round_up ) && absZ1; break;
} default:
} abort();
} }
if ( increment ) { if ( increment ) {
++absZ0; ++absZ0;
@ -206,17 +212,21 @@ static int64 roundAndPackUint64(flag zSign, uint64_t absZ0,
roundingMode = STATUS(float_rounding_mode); roundingMode = STATUS(float_rounding_mode);
roundNearestEven = (roundingMode == float_round_nearest_even); roundNearestEven = (roundingMode == float_round_nearest_even);
switch (roundingMode) {
case float_round_nearest_even:
increment = ((int64_t)absZ1 < 0); increment = ((int64_t)absZ1 < 0);
if (!roundNearestEven) { break;
if (roundingMode == float_round_to_zero) { case float_round_to_zero:
increment = 0; increment = 0;
} else if (absZ1) { break;
if (zSign) { case float_round_up:
increment = (roundingMode == float_round_down) && absZ1; increment = !zSign && absZ1;
} else { break;
increment = (roundingMode == float_round_up) && absZ1; case float_round_down:
} increment = zSign && absZ1;
} break;
default:
abort();
} }
if (increment) { if (increment) {
++absZ0; ++absZ0;
@ -354,20 +364,22 @@ static float32 roundAndPackFloat32(flag zSign, int_fast16_t zExp, uint32_t zSig
roundingMode = STATUS(float_rounding_mode); roundingMode = STATUS(float_rounding_mode);
roundNearestEven = ( roundingMode == float_round_nearest_even ); roundNearestEven = ( roundingMode == float_round_nearest_even );
switch (roundingMode) {
case float_round_nearest_even:
roundIncrement = 0x40; roundIncrement = 0x40;
if ( ! roundNearestEven ) { break;
if ( roundingMode == float_round_to_zero ) { case float_round_to_zero:
roundIncrement = 0; roundIncrement = 0;
} break;
else { case float_round_up:
roundIncrement = 0x7F; roundIncrement = zSign ? 0 : 0x7f;
if ( zSign ) { break;
if ( roundingMode == float_round_up ) roundIncrement = 0; case float_round_down:
} roundIncrement = zSign ? 0x7f : 0;
else { break;
if ( roundingMode == float_round_down ) roundIncrement = 0; default:
} abort();
} break;
} }
roundBits = zSig & 0x7F; roundBits = zSig & 0x7F;
if ( 0xFD <= (uint16_t) zExp ) { if ( 0xFD <= (uint16_t) zExp ) {
@ -536,20 +548,21 @@ static float64 roundAndPackFloat64(flag zSign, int_fast16_t zExp, uint64_t zSig
roundingMode = STATUS(float_rounding_mode); roundingMode = STATUS(float_rounding_mode);
roundNearestEven = ( roundingMode == float_round_nearest_even ); roundNearestEven = ( roundingMode == float_round_nearest_even );
switch (roundingMode) {
case float_round_nearest_even:
roundIncrement = 0x200; roundIncrement = 0x200;
if ( ! roundNearestEven ) { break;
if ( roundingMode == float_round_to_zero ) { case float_round_to_zero:
roundIncrement = 0; roundIncrement = 0;
} break;
else { case float_round_up:
roundIncrement = 0x3FF; roundIncrement = zSign ? 0 : 0x3ff;
if ( zSign ) { break;
if ( roundingMode == float_round_up ) roundIncrement = 0; case float_round_down:
} roundIncrement = zSign ? 0x3ff : 0;
else { break;
if ( roundingMode == float_round_down ) roundIncrement = 0; default:
} abort();
}
} }
roundBits = zSig & 0x3FF; roundBits = zSig & 0x3FF;
if ( 0x7FD <= (uint16_t) zExp ) { if ( 0x7FD <= (uint16_t) zExp ) {
@ -719,19 +732,20 @@ static floatx80
goto precision80; goto precision80;
} }
zSig0 |= ( zSig1 != 0 ); zSig0 |= ( zSig1 != 0 );
if ( ! roundNearestEven ) { switch (roundingMode) {
if ( roundingMode == float_round_to_zero ) { case float_round_nearest_even:
break;
case float_round_to_zero:
roundIncrement = 0; roundIncrement = 0;
} break;
else { case float_round_up:
roundIncrement = roundMask; roundIncrement = zSign ? 0 : roundMask;
if ( zSign ) { break;
if ( roundingMode == float_round_up ) roundIncrement = 0; case float_round_down:
} roundIncrement = zSign ? roundMask : 0;
else { break;
if ( roundingMode == float_round_down ) roundIncrement = 0; default:
} abort();
}
} }
roundBits = zSig0 & roundMask; roundBits = zSig0 & roundMask;
if ( 0x7FFD <= (uint32_t) ( zExp - 1 ) ) { if ( 0x7FFD <= (uint32_t) ( zExp - 1 ) ) {
@ -778,19 +792,21 @@ static floatx80
if ( zSig0 == 0 ) zExp = 0; if ( zSig0 == 0 ) zExp = 0;
return packFloatx80( zSign, zExp, zSig0 ); return packFloatx80( zSign, zExp, zSig0 );
precision80: precision80:
switch (roundingMode) {
case float_round_nearest_even:
increment = ((int64_t)zSig1 < 0); increment = ((int64_t)zSig1 < 0);
if ( ! roundNearestEven ) { break;
if ( roundingMode == float_round_to_zero ) { case float_round_to_zero:
increment = 0; increment = 0;
} break;
else { case float_round_up:
if ( zSign ) { increment = !zSign && zSig1;
increment = ( roundingMode == float_round_down ) && zSig1; break;
} case float_round_down:
else { increment = zSign && zSig1;
increment = ( roundingMode == float_round_up ) && zSig1; break;
} default:
} abort();
} }
if ( 0x7FFD <= (uint32_t) ( zExp - 1 ) ) { if ( 0x7FFD <= (uint32_t) ( zExp - 1 ) ) {
if ( ( 0x7FFE < zExp ) if ( ( 0x7FFE < zExp )
@ -820,16 +836,21 @@ static floatx80
zExp = 0; zExp = 0;
if ( isTiny && zSig1 ) float_raise( float_flag_underflow STATUS_VAR); if ( isTiny && zSig1 ) float_raise( float_flag_underflow STATUS_VAR);
if ( zSig1 ) STATUS(float_exception_flags) |= float_flag_inexact; if ( zSig1 ) STATUS(float_exception_flags) |= float_flag_inexact;
if ( roundNearestEven ) { switch (roundingMode) {
case float_round_nearest_even:
increment = ((int64_t)zSig1 < 0); increment = ((int64_t)zSig1 < 0);
} break;
else { case float_round_to_zero:
if ( zSign ) { increment = 0;
increment = ( roundingMode == float_round_down ) && zSig1; break;
} case float_round_up:
else { increment = !zSign && zSig1;
increment = ( roundingMode == float_round_up ) && zSig1; break;
} case float_round_down:
increment = zSign && zSig1;
break;
default:
abort();
} }
if ( increment ) { if ( increment ) {
++zSig0; ++zSig0;
@ -1029,19 +1050,21 @@ static float128
roundingMode = STATUS(float_rounding_mode); roundingMode = STATUS(float_rounding_mode);
roundNearestEven = ( roundingMode == float_round_nearest_even ); roundNearestEven = ( roundingMode == float_round_nearest_even );
switch (roundingMode) {
case float_round_nearest_even:
increment = ((int64_t)zSig2 < 0); increment = ((int64_t)zSig2 < 0);
if ( ! roundNearestEven ) { break;
if ( roundingMode == float_round_to_zero ) { case float_round_to_zero:
increment = 0; increment = 0;
} break;
else { case float_round_up:
if ( zSign ) { increment = !zSign && zSig2;
increment = ( roundingMode == float_round_down ) && zSig2; break;
} case float_round_down:
else { increment = zSign && zSig2;
increment = ( roundingMode == float_round_up ) && zSig2; break;
} default:
} abort();
} }
if ( 0x7FFD <= (uint32_t) zExp ) { if ( 0x7FFD <= (uint32_t) zExp ) {
if ( ( 0x7FFD < zExp ) if ( ( 0x7FFD < zExp )
@ -1089,16 +1112,21 @@ static float128
zSig0, zSig1, zSig2, - zExp, &zSig0, &zSig1, &zSig2 ); zSig0, zSig1, zSig2, - zExp, &zSig0, &zSig1, &zSig2 );
zExp = 0; zExp = 0;
if ( isTiny && zSig2 ) float_raise( float_flag_underflow STATUS_VAR); if ( isTiny && zSig2 ) float_raise( float_flag_underflow STATUS_VAR);
if ( roundNearestEven ) { switch (roundingMode) {
case float_round_nearest_even:
increment = ((int64_t)zSig2 < 0); increment = ((int64_t)zSig2 < 0);
} break;
else { case float_round_to_zero:
if ( zSign ) { increment = 0;
increment = ( roundingMode == float_round_down ) && zSig2; break;
} case float_round_up:
else { increment = !zSign && zSig2;
increment = ( roundingMode == float_round_up ) && zSig2; break;
} case float_round_down:
increment = zSign && zSig2;
break;
default:
abort();
} }
} }
} }
@ -1737,7 +1765,6 @@ float32 float32_round_to_int( float32 a STATUS_PARAM)
flag aSign; flag aSign;
int_fast16_t aExp; int_fast16_t aExp;
uint32_t lastBitMask, roundBitsMask; uint32_t lastBitMask, roundBitsMask;
int8 roundingMode;
uint32_t z; uint32_t z;
a = float32_squash_input_denormal(a STATUS_VAR); a = float32_squash_input_denormal(a STATUS_VAR);
@ -1769,15 +1796,27 @@ float32 float32_round_to_int( float32 a STATUS_PARAM)
lastBitMask <<= 0x96 - aExp; lastBitMask <<= 0x96 - aExp;
roundBitsMask = lastBitMask - 1; roundBitsMask = lastBitMask - 1;
z = float32_val(a); z = float32_val(a);
roundingMode = STATUS(float_rounding_mode); switch (STATUS(float_rounding_mode)) {
if ( roundingMode == float_round_nearest_even ) { case float_round_nearest_even:
z += lastBitMask>>1; z += lastBitMask>>1;
if ( ( z & roundBitsMask ) == 0 ) z &= ~ lastBitMask; if ((z & roundBitsMask) == 0) {
z &= ~lastBitMask;
} }
else if ( roundingMode != float_round_to_zero ) { break;
if ( extractFloat32Sign( make_float32(z) ) ^ ( roundingMode == float_round_up ) ) { case float_round_to_zero:
break;
case float_round_up:
if (!extractFloat32Sign(make_float32(z))) {
z += roundBitsMask; z += roundBitsMask;
} }
break;
case float_round_down:
if (extractFloat32Sign(make_float32(z))) {
z += roundBitsMask;
}
break;
default:
abort();
} }
z &= ~ roundBitsMask; z &= ~ roundBitsMask;
if ( z != float32_val(a) ) STATUS(float_exception_flags) |= float_flag_inexact; if ( z != float32_val(a) ) STATUS(float_exception_flags) |= float_flag_inexact;
@ -3120,7 +3159,6 @@ static float32 roundAndPackFloat16(flag zSign, int_fast16_t zExp,
int maxexp = ieee ? 29 : 30; int maxexp = ieee ? 29 : 30;
uint32_t mask; uint32_t mask;
uint32_t increment; uint32_t increment;
int8 roundingMode;
bool rounding_bumps_exp; bool rounding_bumps_exp;
bool is_tiny = false; bool is_tiny = false;
@ -3138,8 +3176,7 @@ static float32 roundAndPackFloat16(flag zSign, int_fast16_t zExp,
mask = 0x00001fff; mask = 0x00001fff;
} }
roundingMode = STATUS(float_rounding_mode); switch (STATUS(float_rounding_mode)) {
switch (roundingMode) {
case float_round_nearest_even: case float_round_nearest_even:
increment = (mask + 1) >> 1; increment = (mask + 1) >> 1;
if ((zSig & mask) == increment) { if ((zSig & mask) == increment) {
@ -3430,7 +3467,6 @@ float64 float64_round_to_int( float64 a STATUS_PARAM )
flag aSign; flag aSign;
int_fast16_t aExp; int_fast16_t aExp;
uint64_t lastBitMask, roundBitsMask; uint64_t lastBitMask, roundBitsMask;
int8 roundingMode;
uint64_t z; uint64_t z;
a = float64_squash_input_denormal(a STATUS_VAR); a = float64_squash_input_denormal(a STATUS_VAR);
@ -3463,15 +3499,27 @@ float64 float64_round_to_int( float64 a STATUS_PARAM )
lastBitMask <<= 0x433 - aExp; lastBitMask <<= 0x433 - aExp;
roundBitsMask = lastBitMask - 1; roundBitsMask = lastBitMask - 1;
z = float64_val(a); z = float64_val(a);
roundingMode = STATUS(float_rounding_mode); switch (STATUS(float_rounding_mode)) {
if ( roundingMode == float_round_nearest_even ) { case float_round_nearest_even:
z += lastBitMask >> 1; z += lastBitMask >> 1;
if ( ( z & roundBitsMask ) == 0 ) z &= ~ lastBitMask; if ((z & roundBitsMask) == 0) {
z &= ~lastBitMask;
} }
else if ( roundingMode != float_round_to_zero ) { break;
if ( extractFloat64Sign( make_float64(z) ) ^ ( roundingMode == float_round_up ) ) { case float_round_to_zero:
break;
case float_round_up:
if (!extractFloat64Sign(make_float64(z))) {
z += roundBitsMask; z += roundBitsMask;
} }
break;
case float_round_down:
if (extractFloat64Sign(make_float64(z))) {
z += roundBitsMask;
}
break;
default:
abort();
} }
z &= ~ roundBitsMask; z &= ~ roundBitsMask;
if ( z != float64_val(a) ) if ( z != float64_val(a) )
@ -4699,7 +4747,6 @@ floatx80 floatx80_round_to_int( floatx80 a STATUS_PARAM )
flag aSign; flag aSign;
int32 aExp; int32 aExp;
uint64_t lastBitMask, roundBitsMask; uint64_t lastBitMask, roundBitsMask;
int8 roundingMode;
floatx80 z; floatx80 z;
aExp = extractFloatx80Exp( a ); aExp = extractFloatx80Exp( a );
@ -4740,15 +4787,27 @@ floatx80 floatx80_round_to_int( floatx80 a STATUS_PARAM )
lastBitMask <<= 0x403E - aExp; lastBitMask <<= 0x403E - aExp;
roundBitsMask = lastBitMask - 1; roundBitsMask = lastBitMask - 1;
z = a; z = a;
roundingMode = STATUS(float_rounding_mode); switch (STATUS(float_rounding_mode)) {
if ( roundingMode == float_round_nearest_even ) { case float_round_nearest_even:
z.low += lastBitMask>>1; z.low += lastBitMask>>1;
if ( ( z.low & roundBitsMask ) == 0 ) z.low &= ~ lastBitMask; if ((z.low & roundBitsMask) == 0) {
z.low &= ~lastBitMask;
} }
else if ( roundingMode != float_round_to_zero ) { break;
if ( extractFloatx80Sign( z ) ^ ( roundingMode == float_round_up ) ) { case float_round_to_zero:
break;
case float_round_up:
if (!extractFloatx80Sign(z)) {
z.low += roundBitsMask; z.low += roundBitsMask;
} }
break;
case float_round_down:
if (extractFloatx80Sign(z)) {
z.low += roundBitsMask;
}
break;
default:
abort();
} }
z.low &= ~ roundBitsMask; z.low &= ~ roundBitsMask;
if ( z.low == 0 ) { if ( z.low == 0 ) {
@ -5774,7 +5833,6 @@ float128 float128_round_to_int( float128 a STATUS_PARAM )
flag aSign; flag aSign;
int32 aExp; int32 aExp;
uint64_t lastBitMask, roundBitsMask; uint64_t lastBitMask, roundBitsMask;
int8 roundingMode;
float128 z; float128 z;
aExp = extractFloat128Exp( a ); aExp = extractFloat128Exp( a );
@ -5791,8 +5849,8 @@ float128 float128_round_to_int( float128 a STATUS_PARAM )
lastBitMask = ( lastBitMask<<( 0x406E - aExp ) )<<1; lastBitMask = ( lastBitMask<<( 0x406E - aExp ) )<<1;
roundBitsMask = lastBitMask - 1; roundBitsMask = lastBitMask - 1;
z = a; z = a;
roundingMode = STATUS(float_rounding_mode); switch (STATUS(float_rounding_mode)) {
if ( roundingMode == float_round_nearest_even ) { case float_round_nearest_even:
if ( lastBitMask ) { if ( lastBitMask ) {
add128( z.high, z.low, 0, lastBitMask>>1, &z.high, &z.low ); add128( z.high, z.low, 0, lastBitMask>>1, &z.high, &z.low );
if ( ( z.low & roundBitsMask ) == 0 ) z.low &= ~ lastBitMask; if ( ( z.low & roundBitsMask ) == 0 ) z.low &= ~ lastBitMask;
@ -5803,12 +5861,21 @@ float128 float128_round_to_int( float128 a STATUS_PARAM )
if ( (uint64_t) ( z.low<<1 ) == 0 ) z.high &= ~1; if ( (uint64_t) ( z.low<<1 ) == 0 ) z.high &= ~1;
} }
} }
} break;
else if ( roundingMode != float_round_to_zero ) { case float_round_to_zero:
if ( extractFloat128Sign( z ) break;
^ ( roundingMode == float_round_up ) ) { case float_round_up:
if (!extractFloat128Sign(z)) {
add128(z.high, z.low, 0, roundBitsMask, &z.high, &z.low); add128(z.high, z.low, 0, roundBitsMask, &z.high, &z.low);
} }
break;
case float_round_down:
if (extractFloat128Sign(z)) {
add128(z.high, z.low, 0, roundBitsMask, &z.high, &z.low);
}
break;
default:
abort();
} }
z.low &= ~ roundBitsMask; z.low &= ~ roundBitsMask;
} }
@ -5842,19 +5909,29 @@ float128 float128_round_to_int( float128 a STATUS_PARAM )
roundBitsMask = lastBitMask - 1; roundBitsMask = lastBitMask - 1;
z.low = 0; z.low = 0;
z.high = a.high; z.high = a.high;
roundingMode = STATUS(float_rounding_mode); switch (STATUS(float_rounding_mode)) {
if ( roundingMode == float_round_nearest_even ) { case float_round_nearest_even:
z.high += lastBitMask>>1; z.high += lastBitMask>>1;
if ( ( ( z.high & roundBitsMask ) | a.low ) == 0 ) { if ( ( ( z.high & roundBitsMask ) | a.low ) == 0 ) {
z.high &= ~ lastBitMask; z.high &= ~ lastBitMask;
} }
} break;
else if ( roundingMode != float_round_to_zero ) { case float_round_to_zero:
if ( extractFloat128Sign( z ) break;
^ ( roundingMode == float_round_up ) ) { case float_round_up:
if (!extractFloat128Sign(z)) {
z.high |= ( a.low != 0 ); z.high |= ( a.low != 0 );
z.high += roundBitsMask; z.high += roundBitsMask;
} }
break;
case float_round_down:
if (extractFloat128Sign(z)) {
z.high |= (a.low != 0);
z.high += roundBitsMask;
}
break;
default:
abort();
} }
z.high &= ~ roundBitsMask; z.high &= ~ roundBitsMask;
} }