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AIX Version 4.3 Assembler Language Reference

## mulhw (Multiply High Word) Instruction

### Purpose

Computes the most significant 32 bits of the 64-bit product of two 32-bit integers.

Note: The mulhw instruction is supported only in the PowerPC architecture.

PowerPC
mulhw RT,RA,RB
mulhw. RT,RA,RB

### Description

The mulhw instruction multiplies the contents of general-purpose register (GPR) RA and GPR RB and places the most significant 32 bits of the 64-bit product in the target GPR RT. Both the operands and the product are interpreted as signed integers.

The mulhw instruction has two syntax forms. Each syntax form has a different effect on Condition Register Field 0.

 Syntax Form Record Bit (Rc) Condition Register Field 0 mulhw 0 None mulhw. 1 LT,GT,EQ,SO

If the syntax form sets the Record (Rc) bit to 1, then the Less Than (LT) zero, Greater Than (GT) zero and Equal To (EQ) zero bits in Condition Register Field 0 reflect the result placed in GPR RT, and the Summary Overflow (SO) bit is copied from the XER to the SO bit in Condition Register Field 0.

### Parameters

 RT Specifies target general-purpose register where the result of operation is stored. RA Specifies source general-purpose register for EA calculation. RB Specifies source general-purpose register for EA calculation.

### Examples

1. The following code multiplies the contents of GPR 4 by the contents of GPR 10 and stores the result in GPR 6:
```# Assume GPR 4 contains 0x0000 0003.
# Assume GPR 10 contains 0x0000 0002.
mulhw 6,4,10
# GPR 6 now contains 0x0000 0000.```
2. The following code multiplies the contents of GPR 4 by the contents of GPR 10, stores the result in GPR 6, and sets Condition Register Field 0 to reflect the result of the operation:
```# Assume GPR 4 contains 0x0000 4500.
# Assume GPR 10 contains 0x8000 7000.
# Assume XER(SO) = 0.
mulhw. 6,4,10
# GPR 6 now contains 0xFFFF DD80.
# Condition Register Field 0 now contains 0x4.```

### Related Information

The mul (Multiply) instruction, mulhwu (Multiply High Word Unsigned) instruction, mulli or muli (Multiply Low Immediate) instruction, mullw or muls (Multiply Low Word) instruction.

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