Macchws - IBM PPC440X5 CPU Core User Manual

macchws

Multiply Accumulate Cross Halfword to Word Saturate Signed
PPC440x5 CPU Core User's Manual
macchws
Multiply Accumulate Cross Halfword to Word Saturate Signed
macchws RT, RA, RB
macchws. RT, RA, RB
macchwso RT, RA, RB
macchwso. RT, RA, RB
4
0 6
prod (RA)
0:31 16:31
temp prod + (RT)
0:32 0:31
if ((prod = RT ) (RT
0 0
else (RT) temp
1:32
The low-order halfword of RA is multiplied by the high-order halfword of RB. The signed product is summed
with the contents of RT.
If the signed sum can be represented in 32 bits, then RT is updated with the low-order 32 bits of the signed
sum.
If the signed sum cannot be represented in 32 bits, then RT is updated with a value which is "saturated" to the
nearest representable value. That is, if the signed sum is less than –2
wise, if the signed sum is greater than 2
Registers Altered
• RT
• CR[CR0] if Rc contains 1
• XER[SO, OV] if OE contains 1
Architecture Note
This instruction is implementation-specific and programs which use this instruction may not be portable to
other PowerPC Book-E implementations. See Instruction Set Portability on page 250.
Page 346 of 589
OE=0, Rc=0
OE=0, Rc=1
OE=1, Rc=0
OE=1, Rc=1
RT RA
11
(RB) signed
0:15
temp )) then (RT)
0 1
31
– 1, then RT is updated with 2
RB
16
31
(RT ( RT ))
0 0
31
OE 236
21 22
, then RT is updated with –2
31
– 1.
September 12, 2002
Preliminary
Rc
31
31
. Like-
instrset.fm.