mulhd

Multiply High Doubleword

mulhd RT, RA, RB

Multiplies two 64-bit integers and returns the upper 64 bits of the 128-bit result (Signed).

Details

Multiplies two 64-bit signed integers (RA and RB) and stores the upper 64 bits of the 128-bit signed result in RT. The overflow flag (OE) is not typically set by this instruction as it returns the mathematically correct upper bits. If Rc=1, CR0 is updated based on the result.

Pseudocode Operation

prod ← (RA) *s (RB); RT ← prod[64:127]; if Rc then CR0 ← (RT < 0, RT > 0, RT = 0, SO)

Programming Note

When Rc=1 (dot form), CR0 is updated with the signed comparison of the result against zero (LT, GT, EQ) and the current SO bit from XER.

Example

mulhd r3, r4, r5

Encoding

Binary Layout
31
0
RT
6
RA
11
RB
16
OE
21
73
22
Rc
31
 
Format XO-form
Opcode 0x7C000092
Extension Base
Registers Altered CR0

Operands

  • RT
    Target
  • RA
    Src A
  • RB
    Src B