1/* ldexp.s 4.1 83/06/27 */ 2 3/* 4 * double ldexp (value, exp) 5 * double value; 6 * int exp; 7 * 8 * Ldexp returns value*2**exp, if that result is in range. 9 * If underflow occurs, it returns zero. If overflow occurs, 10 * it returns a value of appropriate sign and largest 11 * possible magnitude. In case of either overflow or underflow, 12 * errno is set to ERANGE. Note that errno is not modified if 13 * no error occurs. 14 */ 15 16#include "DEFS.h" 17#include <errno.h> 18 19 .globl _errno 20 21ENTRY(ldexp) 22 movd 4(ap),r0 /* fetch "value" */ 23 extzv $7,$8,r0,r2 /* r2 := biased exponent */ 24 jeql 1f /* if zero, done */ 25 26 addl2 12(ap),r2 /* r2 := new biased exponent */ 27 jleq 2f /* if <= 0, underflow */ 28 cmpl r2,$256 /* otherwise check if too big */ 29 jgeq 3f /* jump if overflow */ 30 insv r2,$7,$8,r0 /* put exponent back in result */ 311: 32 ret 332: 34 clrd r0 35 jbr 1f 363: 37 movd huge,r0 /* largest possible floating magnitude */ 38 jbc $15,4(ap),1f /* jump if argument was positive */ 39 mnegd r0,r0 /* if arg < 0, make result negative */ 401: 41 movl $ERANGE,_errno 42 ret 43 44 .data 45huge: .word 0x7fff /* the largest number that can */ 46 .word 0xffff /* be represented in a long floating */ 47 .word 0xffff /* number. This is given in hex in order */ 48 .word 0xffff /* to avoid floating conversions */ 49