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| Commit | Line | Data |
|---|---|---|
| 73f2cfac BJ |
1 | /* ldexp.s 4.1 83/06/27 */ |
| 2 | ||
| 3 | /* | |
| 4 | * double ldexp (value, exp) | |
| 5 | * double value; | |
| 6 | * int exp; | |
| 7 | * | |
| 8 | * Ldexp returns value*2**exp, if that result is in range. | |
| 9 | * If underflow occurs, it returns zero. If overflow occurs, | |
| 10 | * it returns a value of appropriate sign and largest | |
| 11 | * possible magnitude. In case of either overflow or underflow, | |
| 12 | * errno is set to ERANGE. Note that errno is not modified if | |
| 13 | * no error occurs. | |
| 14 | */ | |
| 15 | ||
| 16 | #include "DEFS.h" | |
| 17 | #include <errno.h> | |
| 18 | ||
| 19 | .globl _errno | |
| 20 | ||
| 21 | ENTRY(ldexp) | |
| 22 | movd 4(ap),r0 /* fetch "value" */ | |
| 23 | extzv $7,$8,r0,r2 /* r2 := biased exponent */ | |
| 24 | jeql 1f /* if zero, done */ | |
| 25 | ||
| 26 | addl2 12(ap),r2 /* r2 := new biased exponent */ | |
| 27 | jleq 2f /* if <= 0, underflow */ | |
| 28 | cmpl r2,$256 /* otherwise check if too big */ | |
| 29 | jgeq 3f /* jump if overflow */ | |
| 30 | insv r2,$7,$8,r0 /* put exponent back in result */ | |
| 31 | 1: | |
| 32 | ret | |
| 33 | 2: | |
| 34 | clrd r0 | |
| 35 | jbr 1f | |
| 36 | 3: | |
| 37 | movd huge,r0 /* largest possible floating magnitude */ | |
| 38 | jbc $15,4(ap),1f /* jump if argument was positive */ | |
| 39 | mnegd r0,r0 /* if arg < 0, make result negative */ | |
| 40 | 1: | |
| 41 | movl $ERANGE,_errno | |
| 42 | ret | |
| 43 | ||
| 44 | .data | |
| 45 | huge: .word 0x7fff /* the largest number that can */ | |
| 46 | .word 0xffff /* be represented in a long floating */ | |
| 47 | .word 0xffff /* number. This is given in hex in order */ | |
| 48 | .word 0xffff /* to avoid floating conversions */ |