From dc355b764de890e1b5872d0b402dccfd9a9b5286 Mon Sep 17 00:00:00 2001 From: Peter Maydell Date: Tue, 7 Jan 2014 17:19:12 +0000 Subject: 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 Reviewed-by: Richard Henderson --- fpu/softfloat.c | 405 +++++++++++++++++++++++++++++++++----------------------- 1 file changed, 241 insertions(+), 164 deletions(-) diff --git a/fpu/softfloat.c b/fpu/softfloat.c index d4ca7cf7f1..6c7a90a054 100644 --- a/fpu/softfloat.c +++ b/fpu/softfloat.c @@ -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 + /*---------------------------------------------------------------------------- | 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; } -- cgit v1.2.3