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softfloat: Replace countLeadingZeros32/64 with clz32/64
Our minimum required compiler for compiling QEMU is GCC 4.1 these days, so we can drop the support for compilers which do not provide the __builtin_clz*() functions yet. Since the countLeadingZeros32/64 are then identical to the clz32/64 functions, and we do not have to sync the softloat 2 codebase with upstream anymore (softloat 3 is a complete rewrite) we can simply replace the functions with our QEMU versions. Backports commit 0019d5c3a18c31604fb55f9cec3ceb13999c4866 from qemu
This commit is contained in:
Thomas Huth
Lioncash
parent
9f08fb35bc
commit
bd116582e8
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@ -79,17 +79,6 @@ this code that are retained.
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* version 2 or later. See the COPYING file in the top-level directory.
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*/
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/*----------------------------------------------------------------------------
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| This macro tests for minimum version of the GNU C compiler.
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*----------------------------------------------------------------------------*/
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#if defined(__GNUC__) && defined(__GNUC_MINOR__)
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# define SOFTFLOAT_GNUC_PREREQ(maj, min) \
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((__GNUC__ << 16) + __GNUC_MINOR__ >= ((maj) << 16) + (min))
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#else
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# define SOFTFLOAT_GNUC_PREREQ(maj, min) 0
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#endif
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/*----------------------------------------------------------------------------
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| Shifts `a' right by the number of bits given in `count'. If any nonzero
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| bits are shifted off, they are ``jammed'' into the least significant bit of
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@ -712,82 +701,6 @@ static inline uint32_t estimateSqrt32(int aExp, uint32_t a)
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}
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/*----------------------------------------------------------------------------
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| Returns the number of leading 0 bits before the most-significant 1 bit of
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| `a'. If `a' is zero, 32 is returned.
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*----------------------------------------------------------------------------*/
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static inline int8_t countLeadingZeros32(uint32_t a)
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{
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#if SOFTFLOAT_GNUC_PREREQ(3, 4)
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if (a) {
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return __builtin_clz(a);
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} else {
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return 32;
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}
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#else
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static const int8_t countLeadingZerosHigh[] = {
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8, 7, 6, 6, 5, 5, 5, 5, 4, 4, 4, 4, 4, 4, 4, 4,
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3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3,
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2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2,
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2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2,
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1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1,
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1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1,
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1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1,
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1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1,
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0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
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0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
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0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
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0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
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0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
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0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
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0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
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0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0
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};
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int8_t shiftCount;
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shiftCount = 0;
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if ( a < 0x10000 ) {
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shiftCount += 16;
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a <<= 16;
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}
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if ( a < 0x1000000 ) {
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shiftCount += 8;
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a <<= 8;
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}
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shiftCount += countLeadingZerosHigh[ a>>24 ];
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return shiftCount;
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#endif
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}
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/*----------------------------------------------------------------------------
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| Returns the number of leading 0 bits before the most-significant 1 bit of
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| `a'. If `a' is zero, 64 is returned.
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*----------------------------------------------------------------------------*/
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static inline int8_t countLeadingZeros64(uint64_t a)
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{
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#if SOFTFLOAT_GNUC_PREREQ(3, 4)
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if (a) {
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return __builtin_clzll(a);
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} else {
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return 64;
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}
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#else
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int8_t shiftCount;
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shiftCount = 0;
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if ( a < ( (uint64_t) 1 )<<32 ) {
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shiftCount += 32;
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}
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else {
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a >>= 32;
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}
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shiftCount += countLeadingZeros32( (uint32_t)a );
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return shiftCount;
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#endif
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}
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/*----------------------------------------------------------------------------
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| Returns 1 if the 128-bit value formed by concatenating `a0' and `a1'
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| is equal to the 128-bit value formed by concatenating `b0' and `b1'.
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@ -2683,7 +2683,7 @@ static void
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{
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int8_t shiftCount;
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shiftCount = countLeadingZeros32( aSig ) - 8;
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shiftCount = clz32(aSig) - 8;
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*zSigPtr = aSig<<shiftCount;
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*zExpPtr = 1 - shiftCount;
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@ -2791,7 +2791,7 @@ static float32
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{
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int8_t shiftCount;
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shiftCount = countLeadingZeros32( zSig ) - 1;
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shiftCount = clz32(zSig) - 1;
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return roundAndPackFloat32(zSign, zExp - shiftCount, zSig<<shiftCount,
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status);
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@ -2824,7 +2824,7 @@ static void
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{
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int8_t shiftCount;
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shiftCount = countLeadingZeros64( aSig ) - 11;
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shiftCount = clz64(aSig) - 11;
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*zSigPtr = aSig<<shiftCount;
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*zExpPtr = 1 - shiftCount;
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@ -2962,7 +2962,7 @@ static float64
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{
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int8_t shiftCount;
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shiftCount = countLeadingZeros64( zSig ) - 1;
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shiftCount = clz64(zSig) - 1;
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return roundAndPackFloat64(zSign, zExp - shiftCount, zSig<<shiftCount,
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status);
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@ -2980,7 +2980,7 @@ void normalizeFloatx80Subnormal(uint64_t aSig, int32_t *zExpPtr,
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{
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int8_t shiftCount;
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shiftCount = countLeadingZeros64( aSig );
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shiftCount = clz64(aSig);
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*zSigPtr = aSig<<shiftCount;
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*zExpPtr = 1 - shiftCount;
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}
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@ -3219,7 +3219,7 @@ floatx80 normalizeRoundAndPackFloatx80(int8_t roundingPrecision,
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zSig1 = 0;
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zExp -= 64;
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}
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shiftCount = countLeadingZeros64( zSig0 );
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shiftCount = clz64(zSig0);
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shortShift128Left( zSig0, zSig1, shiftCount, &zSig0, &zSig1 );
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zExp -= shiftCount;
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return roundAndPackFloatx80(roundingPrecision, zSign, zExp,
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@ -3296,7 +3296,7 @@ static void
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int8_t shiftCount;
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if ( aSig0 == 0 ) {
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shiftCount = countLeadingZeros64( aSig1 ) - 15;
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shiftCount = clz64(aSig1) - 15;
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if ( shiftCount < 0 ) {
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*zSig0Ptr = aSig1>>( - shiftCount );
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*zSig1Ptr = aSig1<<( shiftCount & 63 );
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@ -3308,7 +3308,7 @@ static void
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*zExpPtr = - shiftCount - 63;
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}
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else {
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shiftCount = countLeadingZeros64( aSig0 ) - 15;
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shiftCount = clz64(aSig0) - 15;
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shortShift128Left( aSig0, aSig1, shiftCount, zSig0Ptr, zSig1Ptr );
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*zExpPtr = 1 - shiftCount;
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}
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@ -3497,7 +3497,7 @@ static float128 normalizeRoundAndPackFloat128(flag zSign, int32_t zExp,
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zSig1 = 0;
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zExp -= 64;
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}
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shiftCount = countLeadingZeros64( zSig0 ) - 15;
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shiftCount = clz64(zSig0) - 15;
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if ( 0 <= shiftCount ) {
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zSig2 = 0;
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shortShift128Left( zSig0, zSig1, shiftCount, &zSig0, &zSig1 );
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@ -3529,7 +3529,7 @@ floatx80 int32_to_floatx80(int32_t a, float_status *status)
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if ( a == 0 ) return packFloatx80( 0, 0, 0 );
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zSign = ( a < 0 );
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absA = zSign ? - a : a;
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shiftCount = countLeadingZeros32( absA ) + 32;
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shiftCount = clz32(absA) + 32;
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zSig = absA;
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return packFloatx80( zSign, 0x403E - shiftCount, zSig<<shiftCount );
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@ -3551,7 +3551,7 @@ float128 int32_to_float128(int32_t a, float_status *status)
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if ( a == 0 ) return packFloat128( 0, 0, 0, 0 );
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zSign = ( a < 0 );
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absA = zSign ? - a : a;
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shiftCount = countLeadingZeros32( absA ) + 17;
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shiftCount = clz32(absA) + 17;
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zSig0 = absA;
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return packFloat128( zSign, 0x402E - shiftCount, zSig0<<shiftCount, 0 );
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@ -3573,7 +3573,7 @@ floatx80 int64_to_floatx80(int64_t a, float_status *status)
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if ( a == 0 ) return packFloatx80( 0, 0, 0 );
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zSign = ( a < 0 );
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absA = zSign ? - a : a;
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shiftCount = countLeadingZeros64( absA );
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shiftCount = clz64(absA);
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return packFloatx80( zSign, 0x403E - shiftCount, absA<<shiftCount );
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}
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@ -3595,7 +3595,7 @@ float128 int64_to_float128(int64_t a, float_status *status)
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if ( a == 0 ) return packFloat128( 0, 0, 0, 0 );
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zSign = ( a < 0 );
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absA = zSign ? - a : a;
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shiftCount = countLeadingZeros64( absA ) + 49;
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shiftCount = clz64(absA) + 49;
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zExp = 0x406E - shiftCount;
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if ( 64 <= shiftCount ) {
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zSig1 = 0;
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