projects / unix-history / blame
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1 | /* |
| 2 | * Copyright (c) 1986 Regents of the University of California. | |
| 3 | * All rights reserved. | |
| 4 | * | |
| 5 | * This code is derived from software contributed to Berkeley by | |
| 6 | * Computer Consoles Inc. | |
| 7 | * | |
| 019bea33 | 8 | * %sccs.include.redist.c% |
| 1f0502d3 KB |
9 | */ |
| 10 | ||
| 11 | #if defined(SYSLIBC_SCCS) && !defined(lint) | |
| 019bea33 | 12 | .asciz "@(#)cvtlf.s 1.3 (Berkeley) %G%" |
| 1f0502d3 | 13 | #endif /* SYSLIBC_SCCS and not lint */ |
| c13f0b2e SL |
14 | |
| 15 | #include <tahoemath/fp.h> | |
| 16 | #include "DEFS.h" | |
| 17 | ||
| 18 | XENTRY(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 | # | |
| 36 | positive: | |
| 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 | |
| 53 | shiftr: | |
| 54 | mnegl r3,r3 | |
| 55 | shrl r3,r0,r0 | |
| 56 | shifted: | |
| 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... | |
| 63 | sign_ok: | |
| 64 | ret | |
| 65 | ||
| 66 | retzero: | |
| 67 | clrl r0 | |
| 68 | ret | |
| 69 | ||
| 70 | retmin: | |
| 71 | movl $0xd0000000,r0 | |
| 72 | ret | |
| 73 | ||
| 74 | ||
| 75 |