6.64.25.2 Basic PowerPC Built-in Functions Available on ISA 2.05 ¶

The basic built-in functions described in this section are available on the PowerPC family of processors starting with ISA 2.05 or later. Unless specific options are explicitly disabled on the command line, specifying option -mcpu=power6 has the effect of enabling the -mpowerpc64, -mpowerpc-gpopt, -mpowerpc-gfxopt, -mmfcrf, -mpopcntb, -mfprnd, -mcmpb, -mhard-dfp, and -mrecip-precision options. Specify the -maltivec option explicitly in combination with the above options if desired.

The following functions require option -mcmpb.

unsigned long long __builtin_cmpb (unsigned long long int, unsigned long long int);
unsigned int __builtin_cmpb (unsigned int, unsigned int);

The __builtin_cmpb function performs a byte-wise compare on the contents of its two arguments, returning the result of the byte-wise comparison as the returned value. For each byte comparison, the corresponding byte of the return value holds 0xff if the input bytes are equal and 0 if the input bytes are not equal. If either of the arguments to this built-in function is wider than 32 bits, the function call expands into the form that expects unsigned long long int arguments which is only available on 64-bit targets.

The following built-in functions are available when hardware decimal floating point (-mhard-dfp) is available:

void __builtin_set_fpscr_drn(int);
_Decimal64 __builtin_ddedpd (int, _Decimal64);
_Decimal128 __builtin_ddedpdq (int, _Decimal128);
_Decimal64 __builtin_denbcd (int, _Decimal64);
_Decimal128 __builtin_denbcdq (int, _Decimal128);
_Decimal64 __builtin_diex (long long, _Decimal64);
_Decimal128 _builtin_diexq (long long, _Decimal128);
_Decimal64 __builtin_dscli (_Decimal64, int);
_Decimal128 __builtin_dscliq (_Decimal128, int);
_Decimal64 __builtin_dscri (_Decimal64, int);
_Decimal128 __builtin_dscriq (_Decimal128, int);
long long __builtin_dxex (_Decimal64);
long long __builtin_dxexq (_Decimal128);
_Decimal128 __builtin_pack_dec128 (unsigned long long, unsigned long long);
unsigned long long __builtin_unpack_dec128 (_Decimal128, int);

The __builtin_set_fpscr_drn builtin allows changing the three decimal
floating point rounding mode bits.  The argument is a 3-bit value.  The
argument can either be a const int or the value can be stored in
a variable.
The builtin uses the ISA 3.0 instruction mffscdrn if available.
Otherwise the builtin reads the FPSCR, masks the current decimal rounding
mode bits out and OR's in the new value.

_Decimal64 __builtin_dfp_quantize (_Decimal64, _Decimal64, const int);
_Decimal64 __builtin_dfp_quantize (const int, _Decimal64, const int);
_Decimal128 __builtin_dfp_quantize (_Decimal128, _Decimal128, const int);
_Decimal128 __builtin_dfp_quantize (const int, _Decimal128, const int);

The __builtin_dfp_quantize built-in, converts and rounds the second
argument to the form with the exponent as specified by the first
argument based on the rounding mode specified by the third argument.
If the first argument is a decimal floating point value, its exponent is used
for converting and rounding of the second argument.  If the first argument is a
5-bit constant integer value, then the value specifies the exponent to be used
when rounding and converting the second argument.  The third argument is a
two bit constant integer that specifies the rounding mode.  The possible modes
are: 00 Round to nearest, ties to even; 01 Round toward 0; 10 Round to nearest,
ties away from 0; 11 Round according to DRN where DRN is the Decimal Floating
point field of the FPSCR.

The following functions require -mhard-float, -mpowerpc-gfxopt, and -mpopcntb options.

double __builtin_recipdiv (double, double);
float __builtin_recipdivf (float, float);
double __builtin_rsqrt (double);
float __builtin_rsqrtf (float);

The vec_rsqrt, __builtin_rsqrt, and __builtin_rsqrtf functions generate multiple instructions to implement the reciprocal sqrt functionality using reciprocal sqrt estimate instructions.

The __builtin_recipdiv, and __builtin_recipdivf functions generate multiple instructions to implement division using the reciprocal estimate instructions.

The following functions require -mhard-float and -mmultiple options.

The __builtin_unpack_longdouble function takes a long double argument and a compile time constant of 0 or 1. If the constant is 0, the first double within the long double is returned, otherwise the second double is returned. The __builtin_unpack_longdouble function is only available if long double uses the IBM extended double representation.

The __builtin_pack_longdouble function takes two double arguments and returns a long double value that combines the two arguments. The __builtin_pack_longdouble function is only available if long double uses the IBM extended double representation.

The __builtin_unpack_ibm128 function takes a __ibm128 argument and a compile time constant of 0 or 1. If the constant is 0, the first double within the __ibm128 is returned, otherwise the second double is returned.

The __builtin_pack_ibm128 function takes two double arguments and returns a __ibm128 value that combines the two arguments.

Additional built-in functions are available for the 64-bit PowerPC family of processors, for efficient use of 128-bit floating point (__float128) values.