120 lines
2.6 KiB
C
120 lines
2.6 KiB
C
#include <assert.h>
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#include <minix/endpoint.h>
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#include <math.h>
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#include "fpu_cw.h"
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#include "fpu_sw.h"
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#define FPUSW_FLAG_MASK \
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(FPUSW_CONDITION_C0 | FPUSW_CONDITION_C2 | FPUSW_CONDITION_C3)
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#define DOUBLE_NORMAL_MIN 2.2250738585072013830902327173324e-308 /* 2^-1022 */
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int fpclassify(double x)
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{
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/* use status word returned by fpu_xam to determine type */
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switch (fpu_xam(x) & FPUSW_FLAG_MASK)
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{
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case FPUSW_CONDITION_C0:
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return FP_NAN;
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case FPUSW_CONDITION_C2:
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/*
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* unfortunately, fxam always operates on long doubles
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* regardless of the precision setting. This means some
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* subnormals are incorrectly classified as normals,
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* since they can be normalized using the additional
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* exponent bits available. However, if we already know
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* that the number is normal as a long double, finding
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* out whether it would be subnormal as a double is just
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* a simple comparison.
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*/
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if (-DOUBLE_NORMAL_MIN < x && x < DOUBLE_NORMAL_MIN)
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return FP_SUBNORMAL;
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else
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return FP_NORMAL;
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case FPUSW_CONDITION_C0 | FPUSW_CONDITION_C2:
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return FP_INFINITE;
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case FPUSW_CONDITION_C3:
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return FP_ZERO;
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case FPUSW_CONDITION_C3 | FPUSW_CONDITION_C2:
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return FP_SUBNORMAL;
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}
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/* we don't expect any other case: unsupported, emtpy or reserved */
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assert(0);
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return -1;
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}
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int signbit(double x)
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{
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u16_t sw;
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/* examine and use status word to determine sign */
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sw = fpu_xam(x);
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return (sw & FPUSW_CONDITION_C1) ? 1 : 0;
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}
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#define FPUSW_GREATER 0
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#define FPUSW_LESS FPUSW_CONDITION_C0
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#define FPUSW_EQUAL FPUSW_CONDITION_C3
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#define FPUSW_UNORDERED \
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(FPUSW_CONDITION_C0 | FPUSW_CONDITION_C2 | FPUSW_CONDITION_C3)
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static int fpcompare(double x, double y, u16_t sw1, u16_t sw2)
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{
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u16_t sw;
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/* compare and check sanity */
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sw = fpu_compare(x, y) & FPUSW_FLAG_MASK;
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switch (sw)
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{
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case FPUSW_GREATER:
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case FPUSW_LESS:
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case FPUSW_EQUAL:
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case FPUSW_UNORDERED:
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break;
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default:
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/* other values are not possible (see IA32 Dev Man) */
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assert(0);
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return -1;
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}
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/* test whether FPUSW equals either sw1 or sw2 */
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return sw == sw1 || sw == sw2;
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}
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int isgreater(double x, double y)
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{
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return fpcompare(x, y, FPUSW_GREATER, -1);
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}
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int isgreaterequal(double x, double y)
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{
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return fpcompare(x, y, FPUSW_GREATER, FPUSW_EQUAL);
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}
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int isless(double x, double y)
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{
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return fpcompare(x, y, FPUSW_LESS, -1);
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}
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int islessequal(double x, double y)
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{
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return fpcompare(x, y, FPUSW_LESS, FPUSW_EQUAL);
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}
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int islessgreater(double x, double y)
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{
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return fpcompare(x, y, FPUSW_LESS, FPUSW_GREATER);
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}
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int isunordered(double x, double y)
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{
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return fpcompare(x, y, FPUSW_UNORDERED, -1);
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}
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