Compaq ECQD2KCTE Laptop User Manual


 
4–36 Alpha Architecture Handbook
4.4.12 Unsigned Quadword Multiply High
Format:
Operation:
Rc {Rav * U Rbv}<127:64>
Exceptions:
Instruction mnemonics:
Qualifiers:
Description:
Register Ra and Rb or a literal are multiplied as unsigned numbers to produce a 128-bit result.
The high-order 64-bits are written to register Rc.
The UMULH instruction can be used to generate the upper 64 bits of a 128-bit result as
follows:
Ra and Rb are unsigned: result of UMULH
Ra and Rb are signed: (result of UMULH) – Ra<63>*Rb – Rb<63>*Ra
The MULQ instruction gives the low 64 bits of the result in either case.
UMULH Ra.rq,Rb.rq,Rc.wq
!Operate format
UMULH Ra.rq,#b.ib,Rc.wq
!Operate format
None
UMULH Unsigned Multiply Quadword High
None