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9-96 PPC405 Core User’s Manual
macchws
Multiply Accumulate Cross Halfword to Word Saturate Signed
macchws
Multiply Accumulate Cross Halfword to Word Saturate Signed
prod
0:31
← (RA)
16:31
x (RB)
0:15
signed
temp
0:32
← prod
0:31
+ (RT)
if ((prod
0
= RT
0
) ∧ (RT
0
≠ temp
1
)) then (RT) ← (RT
0
||
31
(¬RT
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 and the sum is stored in a 33-bit temporary register.
If a result does not overflow, the low-order 32 bits of the temporary register are stored in RT.
If a result overflows, the returned result is the nearest representable value. Thus, if a result is less
than –2
31
, the value stored in RT is –2
31
. Likewise, if a result is greater than 2
31
– 1, the value stored
in RT is 2
31
–1.
Registers Altered
•RT
• CR[CR0]
LT, GT, EQ, SO
if Rc contains 1
• XER[SO, OV] if OE contains 1
Architecture Note
This instruction is part of the Multiply-Accumulate instruction set extensions and complies with the
architectural requirements for APUs of the IBM PowerPC Embedded Environment. As such, it is not
part of the PowerPC Architecture, nor is it part of the IBM PowerPC Embedded Environment.
Programs that use this instruction may not be portable to other implementations.
macchws RT, RA, RB OE=0, Rc=0
macchws. RT, RA, RB OE=0, Rc=1
macchwso RT, RA, RB OE=1, Rc=0
macchwso. RT, RA, RB OE=1, Rc=1
4 RT RA RB OE 236 Rc
0 6 11 16 21 22 31