srw or sr (Shift Right Word) Instruction

[ Previous | Next | Contents | Home | Search ]

AIX Version 4.3 Assembler Language Reference

srw or sr (Shift Right Word) Instruction

Purpose

Rotates the contents of a general-purpose register to the left by a specified number of bits and places the masked result in a general-purpose register.

Syntax

PowerPC
srw	RA,RS,RB
srw.	RA,RS,RB

POWER
sr	RA,RS,RB
sr.	RA,RS,RB

Description

The srw and sr instructions rotate the contents of the source general-purpose register (GPR) RS to the left by 32 minus N bits, where N is the shift amount specified in bits 27-31 of GPR RB, and store the logical AND of the rotated word and the generated mask in GPR RA.

Consider the following when using the srw and sr instructions:

If bit 26 of GPR RB is 0, then a mask of N zeros followed by 32 - N ones is generated.
If bit 26 of GPR RB is 1, then a mask of all zeros is generated.

The srw and sr instruction each have two syntax forms. Each syntax form has a different effect on Condition Register Field 0.

Syntax Form	Overflow Exception (OE)	Fixed-Point Exception Register	Record Bit (Rc)	Condition Register Field 0
srw	None	None	0	None
srw.	None	None	1	LT,GT,EQ,SO
sr	None	None	0	None
sr.	None	None	1	LT,GT,EQ,SO

The two syntax forms of the sr instruction, and the two syntax forms of the srw instruction, never affect the Fixed-Point Exception Register. If the syntax form sets the Record (Rc) bit to 1, these instructions affect the Less Than (LT) zero, Greater Than (GT) zero, Equal To (EQ) zero, and Summary Overflow (SO) bits in Condition Register Field 0.

Parameters

RA	Specifies target general-purpose register where result of operation is stored.
RS	Specifies source general-purpose register for operation.
RB	Specifies source general-purpose register for operation.

Examples

The following code rotates the contents of GPR 4 to the left by 28 bits and stores the result of ANDing the rotated data with a generated mask in GPR 6:
```
# Assume GPR 4 contains 0x9000 3000.
# Assume GPR 5 contains 0x0000 0024.
srw 6,4,5
# GPR 6 now contains 0x0000 0000.
```
The following code rotates the contents of GPR 4 to the left by 28 bits, stores the result of ANDing the rotated data with a generated mask in GPR 6, and sets Condition Register Field 0 to reflect the result of the operation:
```
# Assume GPR 4 contains 0xB004 3001.
# Assume GPR 5 contains 0x0000 0004.
srw. 6,4,5
# GPR 6 now contains 0x0B00 4300.
# Condition Register Field 0 now contains 0x4.
```

Related Information

The addze or aze (Add to Zero Extended) instruction.

Fixed-Point Processor.

Fixed-Point Rotate and Shift Instructions.

[ Previous | Next | Contents | Home | Search ]