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AIX Version 4.3 Assembler Language Reference

mulhdu (Multiply High Double Word Unsigned) Instruction


Multiply 2 unsigned 64-bit values together. Place the high-order 64 bits of the result into a register.


mulhdu RT, RA, RB (Rc=0)
mulhdu. RT, RA, RB (Rc=1)


Both the operands and the product are interpreted as unsigned integers, except that if Rc = 1 (the mulhw. instruction) the first three bits of the condition register 0 field are set by signed comparison of the result to zero.

The 64-bit operands are the contents of RA and RB. The low-order 64 bits of the 128-bit product of the operands are placed into RT.

Other registers altered:

This instruction may execute faster on some implementations if RB contains the operand having the smaller absolute value.


RT Specifies target general-purpose register for the result of the computation.
RA Specifies source general-purpose register for the multiplicand.
RB Specifies source general-purpose register for the multiplier.


This instruction is defined only for 64-bit implementations. Using it on a 32-bit implementation will cause the system illegal instruction error handler to be invoked.

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