projects / unix-history / blame
| Commit | Line | Data |
|---|---|---|
| a6730a00 | 1 | /* Kldexpf.s 1.4 90/12/04 */ |
| 3c2fd3a8 | 2 | |
| 9d1834ba | 3 | #include "../tahoe/SYS.h" |
| a6730a00 KB |
4 | #include "../math/fp.h" |
| 5 | #include "../math/Kfp.h" | |
| 3c2fd3a8 | 6 | |
| 2b252132 SL |
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 | ||
| 3c2fd3a8 | 22 | .text |
| 2b252132 | 23 | ENTRY(Kldexpf, R2) |
| 3c2fd3a8 SL |
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 | /* | |
| 2b252132 SL |
36 | * Construct the result and return |
| 37 | */ | |
| 3c2fd3a8 SL |
38 | andl2 $0!EXPMASK,r0 /* clear old exponent */ |
| 39 | shal $EXPSHIFT,r2,r2 /* Put the exponent back in the result */ | |
| 40 | orl2 r2,r0 | |
| 41 | ld1: ret | |
| 42 | /* | |
| 2b252132 SL |
43 | * Underflow |
| 44 | */ | |
| 3c2fd3a8 SL |
45 | under: clrl r0 /* Result is zero */ |
| 46 | clrl r1 | |
| 47 | orl2 $HFS_UNDF,*16(fp) | |
| 48 | jmp err /* Join general error code */ | |
| 49 | /* | |
| 2b252132 SL |
50 | * Overflow |
| 51 | */ | |
| 3c2fd3a8 SL |
52 | over: 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 | ||
| 57 | err: orl2 $HFS_RANGE,*16(fp) /* Indicate range error */ | |
| 58 | ret | |
| 2b252132 SL |
59 | |
| 60 | .data | |
| 61 | huge0: .long 0x7fffffff | |
| 62 | huge1: .long 0xffffffff |