1/* 2 * Copyright (c) 1983, 1993 3 * The Regents of the University of California. All rights reserved. 4 * 5 * %sccs.include.redist.c% 6 */ 7 8#if defined(LIBC_SCCS) && !defined(lint) 9 .asciz "@(#)ldexp.s 8.1 (Berkeley) 06/04/93" 10#endif /* LIBC_SCCS and not lint */ 11 12/* 13 * double ldexp (value, exp) 14 * double value; 15 * int exp; 16 * 17 * Ldexp returns value*2**exp, if that result is in range. 18 * If underflow occurs, it returns zero. If overflow occurs, 19 * it returns a value of appropriate sign and largest 20 * possible magnitude. In case of either overflow or underflow, 21 * errno is set to ERANGE. Note that errno is not modified if 22 * no error occurs. 23 */ 24 25#include "DEFS.h" 26 27/* 28 * don't include errno.h, ANSI C says it defines errno. 29 * 30 * #include <errno.h> 31 */ 32#define ERANGE 34 33 34 .globl _errno 35 36ENTRY(ldexp, 0) 37 movd 4(ap),r0 /* fetch "value" */ 38 extzv $7,$8,r0,r2 /* r2 := biased exponent */ 39 jeql 1f /* if zero, done */ 40 41 addl2 12(ap),r2 /* r2 := new biased exponent */ 42 jleq 2f /* if <= 0, underflow */ 43 cmpl r2,$256 /* otherwise check if too big */ 44 jgeq 3f /* jump if overflow */ 45 insv r2,$7,$8,r0 /* put exponent back in result */ 461: 47 ret 482: 49 clrd r0 50 jbr 1f 513: 52 movd huge,r0 /* largest possible floating magnitude */ 53 jbc $15,4(ap),1f /* jump if argument was positive */ 54 mnegd r0,r0 /* if arg < 0, make result negative */ 551: 56 movl $ERANGE,_errno 57 ret 58 59 .data 60huge: .word 0x7fff /* the largest number that can */ 61 .word 0xffff /* be represented in a long floating */ 62 .word 0xffff /* number. This is given in hex in order */ 63 .word 0xffff /* to avoid floating conversions */ 64