rlwimi or rlimi (Rotate Left Word Immediate Then Mask Insert) Instruction

Purpose

Rotates the contents of a general-purpose register to the left by a specified number of bits and stores the result in another general-purpose register under the control of a generated mask.

Syntax

See "Extended Mnemonics of Fixed-Point Rotate and Shift Instructions" for more information.

Description

The rlwimi and rlimi instructions rotate left the contents of the source general-purpose register (GPR) RS by the number of bits by the SH parameter and then store the rotated data in GPR RA under control of a 32-bit generated mask defined by the values in Mask Begin (MB) and Mask End (ME). If a mask bit is 1, the instructions place the associated bit of rotated data in GPR RA; if a mask bit is 0, the GPR RA bit remains unchanged.

Consider the following when using the rlwimi and rlimi instructions:

• If the MB value is less than the ME value + 1, then the mask bits between and including the starting point and the end point are set to ones. All other bits are set to zeros.
• If the MB value is the same as the ME value + 1, then all 32 mask bits are set to ones.
• If the MB value is greater than the ME value + 1, then all of the mask bits between and including the ME value +1 and the MB value -1 are set to zeros. All other bits are set to ones.

The BM parameter can also be used to specify the mask for these instructions. The assembler will generate the MB and ME parameters from the BM value.

The rlwimi and rlimi instructions each have two syntax forms. Each syntax form has a different effect on Condition Register Field 0.

The syntax forms of the rlwimi and rlimi instructions never affect the Fixed-Point Exception Register. If the syntax form sets the Record (Rc) bit to 1, the 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

Examples

1. The following code rotates the contents of GPR 4 to the left by 2 bits and stores the masked result in GPR 6:

   # Assume GPR 4 contains 0x9000 3000.
   # Assume GPR 6 contains 0x0000 0003.
   rlwimi 6,4,2,0,0x1D
   # GPR 6 now contains 0x4000 C003.
   # Under the same conditions
   #  rlwimi 6,4,2,0xFFFFFFFC
   # will produce the same result.

2. The following code rotates the contents of GPR 4 to the left by 2 bits, stores the masked result in GPR 6, and sets Condition Register Field 0 to reflect the result of the operation:

   # Assume GPR 4 contains 0x789A 789B.
   # Assume GPR 6 contains 0x3000 0003.
   rlwimi. 6,4,2,0,0x1A
   # GPR 6 now contains 0xE269 E263.
   # CRF 0 now contains 0x8.
   # Under the same conditions
   #  rlwimi. 6,4,2,0xFFFFFFE0
   # will produce the same result.

Related Information

Fixed-Point Processor.

Fixed-Point Rotate and Shift Instructions.