1/* 2 * Copyright (c) 1986, 1993 3 * The Regents of the University of California. All rights reserved. 4 * 5 * This code is derived from software contributed to Berkeley by 6 * Computer Consoles Inc. 7 * 8 * %sccs.include.redist.c% 9 */ 10 11#if defined(SYSLIBC_SCCS) && !defined(lint) 12 .asciz "@(#)cvtlf.s 8.1 (Berkeley) 06/04/93" 13#endif /* SYSLIBC_SCCS and not lint */ 14 15#include <tahoemath/fp.h> 16#include "DEFS.h" 17 18XENTRY(cvtlf, R2|R3|R4|R5) 19 # 20 #Some initializations: 21 # 22 clrl r1 23 clrl r4 # r4 - negative flag. 24 clrl r2 # r2 - exponent. 25 movl 4(fp),r0 # fetch operand. 26 movl r0,r5 # need another copy. 27 jeql retzero # return zero. 28 jgtr positive 29 mnegl r0,r0 30 jvs retmin # return minimum integer. 31 incl r4 # remember it was negative. 32 movl r0,r5 # remember the negated value. 33 # 34 #Compute exponent: 35 # 36positive: 37 ffs r0,r1 38 incl r1 39 addl2 r1,r2 40 shrl r1,r0,r0 41 jneq positive # look for more set bits. 42 # 43 #we have the exponent in r2. 44 # 45 movl r5,r0 # r0 will hold the resulting f.p. number. 46 # 47 #Shift the fraction part to its proper place: 48 # 49 subl3 r2,$HID_POS,r3 50 jlss shiftr # if less then zero we have to shift right. 51 shll r3,r0,r0 # else we shift left. 52 jmp shifted 53shiftr: 54 mnegl r3,r3 55 shrl r3,r0,r0 56shifted: 57 andl2 $CLEARHID,r0 # clear the hidden bit. 58 shal $EXPSHIFT,r2,r2 # shift the exponent to its proper place. 59 orl2 $EXPSIGN,r2 # set the exponent sign bit(to bias it). 60 orl2 r2,r0 # combine exponent & fraction. 61 bbc $0,r4,sign_ok # do we have to set the sign bit? 62 orl2 $SIGNBIT,r0 # yes... 63sign_ok: 64 ret 65 66retzero: 67 clrl r0 68 ret 69 70retmin: 71 movl $0xd0000000,r0 72 ret 73 74 75 76