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Diffstat (limited to 'contrib/gcc/config/rs6000/darwin-ldouble-format')
| -rw-r--r-- | contrib/gcc/config/rs6000/darwin-ldouble-format | 84 |
1 files changed, 0 insertions, 84 deletions
diff --git a/contrib/gcc/config/rs6000/darwin-ldouble-format b/contrib/gcc/config/rs6000/darwin-ldouble-format deleted file mode 100644 index 0012a332d719..000000000000 --- a/contrib/gcc/config/rs6000/darwin-ldouble-format +++ /dev/null @@ -1,84 +0,0 @@ -Long double format -================== - - Each long double is made up of two IEEE doubles. The value of the -long double is the sum of the values of the two parts (except for --0.0). The most significant part is required to be the value of the -long double rounded to the nearest double, as specified by IEEE. For -Inf values, the least significant part is required to be one of +0.0 -or -0.0. No other requirements are made; so, for example, 1.0 may be -represented as (1.0, +0.0) or (1.0, -0.0), and the low part of a NaN -is don't-care. - -Classification --------------- - -A long double can represent any value of the form - s * 2^e * sum(k=0...105: f_k * 2^(-k)) -where 's' is +1 or -1, 'e' is between 1022 and -968 inclusive, f_0 is -1, and f_k for k>0 is 0 or 1. These are the 'normal' long doubles. - -A long double can also represent any value of the form - s * 2^-968 * sum(k=0...105: f_k * 2^(-k)) -where 's' is +1 or -1, f_0 is 0, and f_k for k>0 is 0 or 1. These are -the 'subnormal' long doubles. - -There are four long doubles that represent zero, two that represent -+0.0 and two that represent -0.0. The sign of the high part is the -sign of the long double, and the sign of the low part is ignored. - -Likewise, there are four long doubles that represent infinities, two -for +Inf and two for -Inf. - -Each NaN, quiet or signalling, that can be represented as a 'double' -can be represented as a 'long double'. In fact, there are 2^64 -equivalent representations for each one. - -There are certain other valid long doubles where both parts are -nonzero but the low part represents a value which has a bit set below -2^(e-105). These, together with the subnormal long doubles, make up -the denormal long doubles. - -Many possible long double bit patterns are not valid long doubles. -These do not represent any value. - -Limits ------- - -The maximum representable long double is 2^1024-2^918. The smallest -*normal* positive long double is 2^-968. The smallest denormalised -positive long double is 2^-1074 (this is the same as for 'double'). - -Conversions ------------ - -A double can be converted to a long double by adding a zero low part. - -A long double can be converted to a double by removing the low part. - -Comparisons ------------ - -Two long doubles can be compared by comparing the high parts, and if -those compare equal, comparing the low parts. - -Arithmetic ----------- - -The unary negate operation operates by negating the low and high parts. - -An absolute or absolute-negate operation must be done by comparing -against zero and negating if necessary. - -Addition and subtraction are performed using library routines. They -are not at present performed perfectly accurately, the result produced -will be within 1ulp of the range generated by adding or subtracting -1ulp from the input values, where a 'ulp' is 2^(e-106) given the -exponent 'e'. In the presence of cancellation, this may be -arbitrarily inaccurate. Subtraction is done by negation and addition. - -Multiplication is also performed using a library routine. Its result -will be within 2ulp of the correct result. - -Division is also performed using a library routine. Its result will -be within 3ulp of the correct result. |