A set of extended mnemonics are provided for extract, insert, rotate, shift, clear, and clear left and shift left operations. This article discusses the following:
The alternative input format is applied to the following POWER and PowerPC instructions.
Five operands are normally required for these instructions. These operands are:
RA, RS, SH, MB, ME
MB indicates the first bit with a value of 1 in the mask, and ME indicates the last bit with a value of 1 in the mask. The assembler supports the following operand format.
RA, RS, SH, BM
BM is the mask itself. The assembler generates the MB and ME operands from the BM operand for the instructions. The assembler checks the BM operand first. If an invalid BM is entered, error 78 is reported.
A valid mask is defined as a single series (one or more) of bits with a value of 1 surrounded by zero or more bits with a value of z0. A mask of all bits with a value of 0 may not be specified.
The extended mnemonics for the rotate and shift instructions are in the POWER and PowerPC intersection area (com assembly mode). A set of rotate and shift extended mnemonics provide for the following operations:
|Extract||Selects a field of n bits starting at bit position b in the source register. This field is right- or left-justified in the target register. All other bits of the target register are cleared to 0.|
|Insert||Selects a left- or right-justified field of n bits in the source register. This field is inserted starting at bit position b of the target register. Other bits of the target register are unchanged. No extended mnemonic is provided for insertion of a left-justified field when operating on doublewords, since such an insertion requires more than one instruction.|
|Rotate||Rotates the contents of a register right or left n bits without masking.|
|Shift||Shifts the contents of a register right or left n bits. Vacated bits are cleared to 0 (logical shift).|
|Clear||Clears the leftmost or rightmost n bits of a register to 0.|
|Clear left and shift left||Clears the leftmost b bits of a register, then shifts the register by n bits. This operation can be used to scale a known nonnegative array index by the width of an element.|
The rotate and shift extended mnemonics are shown in the following table. The N operand specifies the number of bits to be extracted, inserted, rotated, or shifted. Because expressions are introduced when the extended mnemonics are mapped to the base mnemonics, certain restrictions are imposed to prevent the result of the expression from causing an overflow in the SH, MB, or ME operand.
To maintain compatibility with previous versions of AIX, n is not restricted to a value of 0. If n is 0, the assembler treats 32-n as a value of 0.
|63-bit Rotate and Shift Extended Mnemonics for PowerPC|
|Operation||Extended Mnemonic||Equivalent to||Restrictions|
|Extract double word and right justify immediate||extrdi RA, RS, n, b||rldicl RA, RS, b + n, 64 - n||n > 0|
|Rotate double word left immediate||rotldi RA, RS, n||rldicl RA, RS, n, 0||None|
|Rotate double word right immediate||rotrdi RA, RS, n||rldicl RA, RS, 64 - n, 0||None|
|Rotate double word right immediate||srdi RA, RS, n||rldicl RA, RS, 64 - n, n||n < 64|
|Clear left double word immediate||clrldi RA, RS, n||rldicl RA, RS, 0, n||n < 64|
|Extract double word and left justify immediate||extldi RA, RS, n, b||rldicr RA, RS, b, n - 1||None|
|Shift left double word immediate||sldi RA, RS, n||rldicr RA, RS, n, 63 - n||None|
|Clear right double word immediate||clrrdi RA, RS, n||rldicr RA, RS, 0, 63 - n||None|
|Clear left double word and shift left immediate||clrlsldi RA, RS, b, n||rldic RA, RS, n, b - n||None|
|Insert double word from right immediate||insrdi RA, RS, n, b||rldimi RA, RS, 64 - (b + n), b||None|
|Rotate double word left||rotld RA, RS, RB||rldcl RA, RS, RB, 0||None|
Note: All of these extended mnemonics can be coded with a final . (period) to cause the Rc bit to be set in the underlying instruction.
Extended Instruction Mnemonics Overview.
Extended Mnemonics of Branch Instructions.
Extended Mnemonics of Condition Register Logical Instructions.
Extended Mnemonics of Fixed-Point Arithmetic Instructions.
Extended Mnemonics of Fixed-Point Compare Instructions.
Extended Mnemonics of Fixed-Point Load Instructions.
Extended Mnemonics of Fixed-Point Logical Instructions.
Extended Mnemonics of Fixed-Point Trap Instructions.
Extended Mnemonics of Moving from or to Special-Purpose Registers.
The rlwinm or rlinm (Rotate Left Word Immediate Then AND with Mask) instruction.