1/* Kldexpf.s 1.3 86/01/05 */ 2 3#include "../tahoe/SYS.h" 4#include "../tahoemath/fp.h" 5#include "../tahoemath/Kfp.h" 6 7/* @(*)Kldexpf.s 4.2 (Berkeley) 12/21/80 8 * Tahoe 2/2/83 9 * 10 * float Kldexpf (op_most, op_least, exp, hfs) 11 * 12 * Ldexp returns value*2**exp, if that result is in range. 13 * If underflow occurs, it returns zero. If overflow occurs, 14 * it returns a value of appropriate sign and largest 15 * possible magnitude. In case of either overflow or underflow, 16 * the external int "errno" is set to ERANGE. Note that errno is 17 * not modified if no error occurs, so if you intend to test it 18 * after you use Kldexpf, you had better set it to something 19 * other than ERANGE first (zero is a reasonable value to use). 20 */ 21 22 .text 23ENTRY(Kldexpf, R2) 24 movl 4(fp),r0 /* Fetch "value" */ 25 movl 8(fp),r1 26 27 andl3 $EXPMASK,r0,r2 /* r2 := shifted biased exponent */ 28 jeql ld1 /* If it's zero, we're done */ 29 shar $EXPSHIFT,r2,r2 /* shift to get value of exponent */ 30 31 addl2 12(fp),r2 /* r2 := new biased exponent */ 32 jleq under /* if it's <= 0, we have an underflow */ 33 cmpl r2,$256 /* Otherwise check if it's too big */ 34 jgeq over /* jump if overflow */ 35/* 36 * Construct the result and return 37 */ 38 andl2 $0!EXPMASK,r0 /* clear old exponent */ 39 shal $EXPSHIFT,r2,r2 /* Put the exponent back in the result */ 40 orl2 r2,r0 41ld1: ret 42/* 43 * Underflow 44 */ 45under: clrl r0 /* Result is zero */ 46 clrl r1 47 orl2 $HFS_UNDF,*16(fp) 48 jmp err /* Join general error code */ 49/* 50 * Overflow 51 */ 52over: movl huge0,r0 /* Largest possible floating magnitude */ 53 movl huge1,r1 54 orl2 $HFS_OVF,*16(fp) 55 orl2 $SIGNBIT,r0 /* If arg < 0, make result negative */ 56 57err: orl2 $HFS_RANGE,*16(fp) /* Indicate range error */ 58 ret 59 60 .data 61huge0: .long 0x7fffffff 62huge1: .long 0xffffffff 63