mirror of
https://github.com/SEPPDROID/Digital-Research-Source-Code.git
synced 2025-10-23 00:14:25 +00:00
129 lines
6.3 KiB
ArmAsm
129 lines
6.3 KiB
ArmAsm
ttl ieee format equivalent add/subtract (iefadd/iefsub)
|
||
***************************************
|
||
* (c) copyright 1981 by motorola inc. *
|
||
***************************************
|
||
|
||
*************************************************************
|
||
* iefadd/iefsub *
|
||
* fast floating point ieee format equivalent add/subtract *
|
||
* *
|
||
* iefadd - ieee format equivalent floating point addition *
|
||
* *
|
||
* input: d6 - ieee format number addend (source) *
|
||
* d7 - ieee format number adder (destination) *
|
||
* *
|
||
* iefsub - ieee format equivalent floating point subtract *
|
||
* *
|
||
* input: d6 - ieee format number subtrahend (source) *
|
||
* d7 - ieee format number minuend (destination) *
|
||
* *
|
||
* output: d7 - ieee format floating result of register d6 *
|
||
* added or subtracted from register d7 *
|
||
* *
|
||
* condition codes: *
|
||
* n - result is negative *
|
||
* z - result is zero *
|
||
* v - result is nan (not-a-number) *
|
||
* c - undefined *
|
||
* x - undefined *
|
||
* *
|
||
* all registers transparent *
|
||
* *
|
||
* maximum used stack: 28 bytes *
|
||
* *
|
||
* result matrix: arg 2 *
|
||
* others +inf -inf nan *
|
||
* arg 1 **************************************** *
|
||
* others * a * b * c * f * *
|
||
* +infinity * b * b * d * f * *
|
||
* -infinity * c * d * c * f * *
|
||
* nan * e * e * e * f * *
|
||
* **************************************** *
|
||
* a = return addition or subtraction result, *
|
||
* overflowing to infinity, underflowing to zero *
|
||
* b = return plus infinity *
|
||
* c = return minus infinity *
|
||
* d = return newly created nan (not-a-number) *
|
||
* e = return arg1 (nan) unchanged *
|
||
* f = return arg2 (nan) unchanged *
|
||
* *
|
||
* notes: *
|
||
* 1) for subtraction, the sign of the source is *
|
||
* inverted and then the operation is treated as *
|
||
* an addition using the decision matrix above. *
|
||
* 2) see the mc68344 user's guide for a description of *
|
||
* the possible differences between the results *
|
||
* returned here versus those required by the *
|
||
* ieee standard. *
|
||
* *
|
||
*************************************************************
|
||
page
|
||
iefadd idnt 1,1 ieee format equivalent add/subtract
|
||
|
||
opt pcs
|
||
|
||
xdef iefadd ieee format addition
|
||
xdef iefsub ieee format subtraction
|
||
|
||
xref iefdop double argument conversion routine
|
||
xref iefrtnan create and return nan result routine
|
||
xref iefrtd7 return contents of d7 as the result
|
||
xref iefrtsz return signed zero with sign of d7
|
||
xref ieftieee return and convert back to ieee format
|
||
xref ffpadd reference fast floating point add routine
|
||
xref ffpcpyrt copyright notice
|
||
|
||
section 9
|
||
|
||
************************
|
||
* subtract entry point *
|
||
************************
|
||
iefsub bchg.l #31,d6 invert sign of second argument for subtract
|
||
jsr iefadd and call add routine
|
||
move.w sr,-(sp) save ccr of result on the stack [vlh] was sr
|
||
bchg.l #31,d6 revert sign back to original condition
|
||
rtr return with result and condition codes
|
||
|
||
*******************
|
||
* add entry point *
|
||
*******************
|
||
iefadd jsr iefdop decode both operands
|
||
bra.s iefnrm +0 branch normalized
|
||
bra.s iefinf2 +2 branch arg2 infinity
|
||
bra.s iefinf1 +4 branch arg1 infinity
|
||
* test for opposite signs +6 both are infinity
|
||
eor.l d6,d7 exclusive or signs
|
||
* bmi iefrtnan opposite signs - go return a nan
|
||
bmi GOTHERE
|
||
jmp iefinf1
|
||
GOTHERE jmp iefrtnan * loader problem
|
||
|
||
* otherwise both same and return same
|
||
|
||
* arg1 infinity - return it
|
||
iefinf1 move.l d6,d7 return arg1
|
||
* arg2 infinity - return it (already in d7)
|
||
iefinf2 jmp iefrtd7 return d7 as our result
|
||
|
||
* normalized numbers - do the addition
|
||
iefnrm jsr ffpadd do fast floating point add
|
||
* bne ieftieee convert result back to ieee format
|
||
bne DOIT
|
||
jmp NOPE
|
||
DOIT jmp ieftieee
|
||
* the above few lines had to be changed because of the loader problem
|
||
|
||
* result is zero - return with proper sign for rn (round-to-nearest)
|
||
NOPE
|
||
movem.l (sp),d3-d7 reload arguments (and rest of registers)
|
||
and.l d6,d7 return minus only if both minus
|
||
jmp iefrtsz return signed zero with sign of d7
|
||
|
||
end
|
||
|
||
z return signed zero with sign of d7
|
||
|
||
end
|
||
|
||
z return signed zero with sign of d7
|
||
|
||
end
|
||
|
||
|