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提交 dc355b76 编写于 作者: P Peter Maydell
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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: NPeter Maydell <peter.maydell@linaro.org>
Reviewed-by: NRichard Henderson <rth@twiddle.net>
上级 14c9a07e
隐藏空白更改
内联 并排
Showing with 241 addition and 164 deletion
fpu/softfloat.c
浏览文件 @ dc355b76
......@@ -42,6 +42,9 @@ these four paragraphs for those parts of this code that are retained.
#include "fpu/softfloat.h"
/* We only need stdlib for abort() */
#include <stdlib.h>
/*----------------------------------------------------------------------------
| Primitive arithmetic functions, including multi-word arithmetic, and
| 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);
roundNearestEven = ( roundingMode == float_round_nearest_even );
roundIncrement = 0x40;
if ( ! roundNearestEven ) {
if ( roundingMode == float_round_to_zero ) {
roundIncrement = 0;
}
else {
roundIncrement = 0x7F;
if ( zSign ) {
if ( roundingMode == float_round_up ) roundIncrement = 0;
}
else {
if ( roundingMode == float_round_down ) roundIncrement = 0;
}
}
switch (roundingMode) {
case float_round_nearest_even:
roundIncrement = 0x40;
break;
case float_round_to_zero:
roundIncrement = 0;
break;
case float_round_up:
roundIncrement = zSign ? 0 : 0x7f;
break;
case float_round_down:
roundIncrement = zSign ? 0x7f : 0;
break;
default:
abort();
}
roundBits = absZ & 0x7F;
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);
roundNearestEven = ( roundingMode == float_round_nearest_even );
increment = ( (int64_t) absZ1 < 0 );
if ( ! roundNearestEven ) {
if ( roundingMode == float_round_to_zero ) {
increment = 0;
}
else {
if ( zSign ) {
increment = ( roundingMode == float_round_down ) && absZ1;
}
else {
increment = ( roundingMode == float_round_up ) && absZ1;
}
}
switch (roundingMode) {
case float_round_nearest_even:
increment = ((int64_t) absZ1 < 0);
break;
case float_round_to_zero:
increment = 0;
break;
case float_round_up:
increment = !zSign && absZ1;
break;
case float_round_down:
increment = zSign && absZ1;
break;
default:
abort();
}
if ( increment ) {
++absZ0;
......@@ -206,17 +212,21 @@ static int64 roundAndPackUint64(flag zSign, uint64_t absZ0,
roundingMode = STATUS(float_rounding_mode);
roundNearestEven = (roundingMode == float_round_nearest_even);
increment = ((int64_t)absZ1 < 0);
if (!roundNearestEven) {
if (roundingMode == float_round_to_zero) {
increment = 0;
} else if (absZ1) {
if (zSign) {
increment = (roundingMode == float_round_down) && absZ1;
} else {
increment = (roundingMode == float_round_up) && absZ1;
}
}
switch (roundingMode) {
case float_round_nearest_even:
increment = ((int64_t)absZ1 < 0);
break;
case float_round_to_zero:
increment = 0;
break;
case float_round_up:
increment = !zSign && absZ1;
break;
case float_round_down:
increment = zSign && absZ1;
break;
default:
abort();
}
if (increment) {
++absZ0;
......@@ -354,20 +364,22 @@ static float32 roundAndPackFloat32(flag zSign, int_fast16_t zExp, uint32_t zSig
roundingMode = STATUS(float_rounding_mode);
roundNearestEven = ( roundingMode == float_round_nearest_even );
roundIncrement = 0x40;
if ( ! roundNearestEven ) {
if ( roundingMode == float_round_to_zero ) {
roundIncrement = 0;
}
else {
roundIncrement = 0x7F;
if ( zSign ) {
if ( roundingMode == float_round_up ) roundIncrement = 0;
}
else {
if ( roundingMode == float_round_down ) roundIncrement = 0;
}
}
switch (roundingMode) {
case float_round_nearest_even:
roundIncrement = 0x40;
break;
case float_round_to_zero:
roundIncrement = 0;
break;
case float_round_up:
roundIncrement = zSign ? 0 : 0x7f;
break;
case float_round_down:
roundIncrement = zSign ? 0x7f : 0;
break;
default:
abort();
break;
}
roundBits = zSig & 0x7F;
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);
roundNearestEven = ( roundingMode == float_round_nearest_even );
roundIncrement = 0x200;
if ( ! roundNearestEven ) {
if ( roundingMode == float_round_to_zero ) {
roundIncrement = 0;
}
else {
roundIncrement = 0x3FF;
if ( zSign ) {
if ( roundingMode == float_round_up ) roundIncrement = 0;
}
else {
if ( roundingMode == float_round_down ) roundIncrement = 0;
}
}
switch (roundingMode) {
case float_round_nearest_even:
roundIncrement = 0x200;
break;
case float_round_to_zero:
roundIncrement = 0;
break;
case float_round_up:
roundIncrement = zSign ? 0 : 0x3ff;
break;
case float_round_down:
roundIncrement = zSign ? 0x3ff : 0;
break;
default:
abort();
}
roundBits = zSig & 0x3FF;
if ( 0x7FD <= (uint16_t) zExp ) {
......@@ -719,19 +732,20 @@ static floatx80
goto precision80;
}
zSig0 |= ( zSig1 != 0 );
if ( ! roundNearestEven ) {
if ( roundingMode == float_round_to_zero ) {
roundIncrement = 0;
}
else {
roundIncrement = roundMask;
if ( zSign ) {
if ( roundingMode == float_round_up ) roundIncrement = 0;
}
else {
if ( roundingMode == float_round_down ) roundIncrement = 0;
}
}
switch (roundingMode) {
case float_round_nearest_even:
break;
case float_round_to_zero:
roundIncrement = 0;
break;
case float_round_up:
roundIncrement = zSign ? 0 : roundMask;
break;
case float_round_down:
roundIncrement = zSign ? roundMask : 0;
break;
default:
abort();
}
roundBits = zSig0 & roundMask;
if ( 0x7FFD <= (uint32_t) ( zExp - 1 ) ) {
......@@ -778,19 +792,21 @@ static floatx80
if ( zSig0 == 0 ) zExp = 0;
return packFloatx80( zSign, zExp, zSig0 );
precision80:
increment = ( (int64_t) zSig1 < 0 );
if ( ! roundNearestEven ) {
if ( roundingMode == float_round_to_zero ) {
increment = 0;
}
else {
if ( zSign ) {
increment = ( roundingMode == float_round_down ) && zSig1;
}
else {
increment = ( roundingMode == float_round_up ) && zSig1;
}
}
switch (roundingMode) {
case float_round_nearest_even:
increment = ((int64_t)zSig1 < 0);
break;
case float_round_to_zero:
increment = 0;
break;
case float_round_up:
increment = !zSign && zSig1;
break;
case float_round_down:
increment = zSign && zSig1;
break;
default:
abort();
}
if ( 0x7FFD <= (uint32_t) ( zExp - 1 ) ) {
if ( ( 0x7FFE < zExp )
......@@ -820,16 +836,21 @@ static floatx80
zExp = 0;
if ( isTiny && zSig1 ) float_raise( float_flag_underflow STATUS_VAR);
if ( zSig1 ) STATUS(float_exception_flags) |= float_flag_inexact;
if ( roundNearestEven ) {
increment = ( (int64_t) zSig1 < 0 );
}
else {
if ( zSign ) {
increment = ( roundingMode == float_round_down ) && zSig1;
}
else {
increment = ( roundingMode == float_round_up ) && zSig1;
}
switch (roundingMode) {
case float_round_nearest_even:
increment = ((int64_t)zSig1 < 0);
break;
case float_round_to_zero:
increment = 0;
break;
case float_round_up:
increment = !zSign && zSig1;
break;
case float_round_down:
increment = zSign && zSig1;
break;
default:
abort();
}
if ( increment ) {
++zSig0;
......@@ -1029,19 +1050,21 @@ static float128
roundingMode = STATUS(float_rounding_mode);
roundNearestEven = ( roundingMode == float_round_nearest_even );
increment = ( (int64_t) zSig2 < 0 );
if ( ! roundNearestEven ) {
if ( roundingMode == float_round_to_zero ) {
increment = 0;
}
else {
if ( zSign ) {
increment = ( roundingMode == float_round_down ) && zSig2;
}
else {
increment = ( roundingMode == float_round_up ) && zSig2;
}
}
switch (roundingMode) {
case float_round_nearest_even:
increment = ((int64_t)zSig2 < 0);
break;
case float_round_to_zero:
increment = 0;
break;
case float_round_up:
increment = !zSign && zSig2;
break;
case float_round_down:
increment = zSign && zSig2;
break;
default:
abort();
}
if ( 0x7FFD <= (uint32_t) zExp ) {
if ( ( 0x7FFD < zExp )
......@@ -1089,16 +1112,21 @@ static float128
zSig0, zSig1, zSig2, - zExp, &zSig0, &zSig1, &zSig2 );
zExp = 0;
if ( isTiny && zSig2 ) float_raise( float_flag_underflow STATUS_VAR);
if ( roundNearestEven ) {
increment = ( (int64_t) zSig2 < 0 );
}
else {
if ( zSign ) {
increment = ( roundingMode == float_round_down ) && zSig2;
}
else {
increment = ( roundingMode == float_round_up ) && zSig2;
}
switch (roundingMode) {
case float_round_nearest_even:
increment = ((int64_t)zSig2 < 0);
break;
case float_round_to_zero:
increment = 0;
break;
case float_round_up:
increment = !zSign && 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;
int_fast16_t aExp;
uint32_t lastBitMask, roundBitsMask;
int8 roundingMode;
uint32_t z;
a = float32_squash_input_denormal(a STATUS_VAR);
......@@ -1769,15 +1796,27 @@ float32 float32_round_to_int( float32 a STATUS_PARAM)
lastBitMask <<= 0x96 - aExp;
roundBitsMask = lastBitMask - 1;
z = float32_val(a);
roundingMode = STATUS(float_rounding_mode);
if ( roundingMode == float_round_nearest_even ) {
switch (STATUS(float_rounding_mode)) {
case float_round_nearest_even:
z += lastBitMask>>1;
if ( ( z & roundBitsMask ) == 0 ) z &= ~ lastBitMask;
}
else if ( roundingMode != float_round_to_zero ) {
if ( extractFloat32Sign( make_float32(z) ) ^ ( roundingMode == float_round_up ) ) {
if ((z & roundBitsMask) == 0) {
z &= ~lastBitMask;
}
break;
case float_round_to_zero:
break;
case float_round_up:
if (!extractFloat32Sign(make_float32(z))) {
z += roundBitsMask;
}
break;
case float_round_down:
if (extractFloat32Sign(make_float32(z))) {
z += roundBitsMask;
}
break;
default:
abort();
}
z &= ~ roundBitsMask;
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;
uint32_t mask;
uint32_t increment;
int8 roundingMode;
bool rounding_bumps_exp;
bool is_tiny = false;
......@@ -3138,8 +3176,7 @@ static float32 roundAndPackFloat16(flag zSign, int_fast16_t zExp,
mask = 0x00001fff;
}
roundingMode = STATUS(float_rounding_mode);
switch (roundingMode) {
switch (STATUS(float_rounding_mode)) {
case float_round_nearest_even:
increment = (mask + 1) >> 1;
if ((zSig & mask) == increment) {
......@@ -3430,7 +3467,6 @@ float64 float64_round_to_int( float64 a STATUS_PARAM )
flag aSign;
int_fast16_t aExp;
uint64_t lastBitMask, roundBitsMask;
int8 roundingMode;
uint64_t z;
a = float64_squash_input_denormal(a STATUS_VAR);
......@@ -3463,15 +3499,27 @@ float64 float64_round_to_int( float64 a STATUS_PARAM )
lastBitMask <<= 0x433 - aExp;
roundBitsMask = lastBitMask - 1;
z = float64_val(a);
roundingMode = STATUS(float_rounding_mode);
if ( roundingMode == float_round_nearest_even ) {
z += lastBitMask>>1;
if ( ( z & roundBitsMask ) == 0 ) z &= ~ lastBitMask;
}
else if ( roundingMode != float_round_to_zero ) {
if ( extractFloat64Sign( make_float64(z) ) ^ ( roundingMode == float_round_up ) ) {
switch (STATUS(float_rounding_mode)) {
case float_round_nearest_even:
z += lastBitMask >> 1;
if ((z & roundBitsMask) == 0) {
z &= ~lastBitMask;
}
break;
case float_round_to_zero:
break;
case float_round_up:
if (!extractFloat64Sign(make_float64(z))) {
z += roundBitsMask;
}
break;
case float_round_down:
if (extractFloat64Sign(make_float64(z))) {
z += roundBitsMask;
}
break;
default:
abort();
}
z &= ~ roundBitsMask;
if ( z != float64_val(a) )
......@@ -4699,7 +4747,6 @@ floatx80 floatx80_round_to_int( floatx80 a STATUS_PARAM )
flag aSign;
int32 aExp;
uint64_t lastBitMask, roundBitsMask;
int8 roundingMode;
floatx80 z;
aExp = extractFloatx80Exp( a );
......@@ -4740,15 +4787,27 @@ floatx80 floatx80_round_to_int( floatx80 a STATUS_PARAM )
lastBitMask <<= 0x403E - aExp;
roundBitsMask = lastBitMask - 1;
z = a;
roundingMode = STATUS(float_rounding_mode);
if ( roundingMode == float_round_nearest_even ) {
switch (STATUS(float_rounding_mode)) {
case float_round_nearest_even:
z.low += lastBitMask>>1;
if ( ( z.low & roundBitsMask ) == 0 ) z.low &= ~ lastBitMask;
}
else if ( roundingMode != float_round_to_zero ) {
if ( extractFloatx80Sign( z ) ^ ( roundingMode == float_round_up ) ) {
if ((z.low & roundBitsMask) == 0) {
z.low &= ~lastBitMask;
}
break;
case float_round_to_zero:
break;
case float_round_up:
if (!extractFloatx80Sign(z)) {
z.low += roundBitsMask;
}
break;
case float_round_down:
if (extractFloatx80Sign(z)) {
z.low += roundBitsMask;
}
break;
default:
abort();
}
z.low &= ~ roundBitsMask;
if ( z.low == 0 ) {
......@@ -5774,7 +5833,6 @@ float128 float128_round_to_int( float128 a STATUS_PARAM )
flag aSign;
int32 aExp;
uint64_t lastBitMask, roundBitsMask;
int8 roundingMode;
float128 z;
aExp = extractFloat128Exp( a );
......@@ -5791,8 +5849,8 @@ float128 float128_round_to_int( float128 a STATUS_PARAM )
lastBitMask = ( lastBitMask<<( 0x406E - aExp ) )<<1;
roundBitsMask = lastBitMask - 1;
z = a;
roundingMode = STATUS(float_rounding_mode);
if ( roundingMode == float_round_nearest_even ) {
switch (STATUS(float_rounding_mode)) {
case float_round_nearest_even:
if ( lastBitMask ) {
add128( z.high, z.low, 0, lastBitMask>>1, &z.high, &z.low );
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;
}
}
}
else if ( roundingMode != float_round_to_zero ) {
if ( extractFloat128Sign( z )
^ ( roundingMode == float_round_up ) ) {
add128( z.high, z.low, 0, roundBitsMask, &z.high, &z.low );
break;
case float_round_to_zero:
break;
case float_round_up:
if (!extractFloat128Sign(z)) {
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;
}
......@@ -5842,19 +5909,29 @@ float128 float128_round_to_int( float128 a STATUS_PARAM )
roundBitsMask = lastBitMask - 1;
z.low = 0;
z.high = a.high;
roundingMode = STATUS(float_rounding_mode);
if ( roundingMode == float_round_nearest_even ) {
switch (STATUS(float_rounding_mode)) {
case float_round_nearest_even:
z.high += lastBitMask>>1;
if ( ( ( z.high & roundBitsMask ) | a.low ) == 0 ) {
z.high &= ~ lastBitMask;
}
}
else if ( roundingMode != float_round_to_zero ) {
if ( extractFloat128Sign( z )
^ ( roundingMode == float_round_up ) ) {
break;
case float_round_to_zero:
break;
case float_round_up:
if (!extractFloat128Sign(z)) {
z.high |= ( a.low != 0 );
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;
}
......
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