Freescale Semiconductor PowerPC e500 Core, Reference Manual

Page: 446 / 548

PowerPC e500 Core Family Reference Manual, Rev. 1
C-2 Freescale Semiconductor
Simplified Mnemonics for PowerPC Instructions
C.2 Subtract Simplified Mnemonics
This section describes simplified mnemonics for subtract instructions.
C.2.1 Subtract Immediate
There is no subtract immediate instruction, however, its effect is achieved by negating the
immediate operand of an Add Immediate instruction, addi. Simplified mnemonics include this
negation, making the intent of the computation more clear. These are listed in
Table C-1 .
C.2.2 Subtract
Subtract from instructions subtract the second operand (rA) from the third (rB). The simplified
mnemonics in
Table C-2 use the more common order in which the third operand is subtracted from
the second.
C.3 Rotate and Shift Simplified Mnemonics
Rotate and shift instructions provide powerful, general ways to manipulate register contents, but
can be difficult to understand. Simplified mnemonics are provided for the following operations:
• Extract—Select a field of n bits starting at bit position b in the source register; left or right
justify this field in the target register; clear all other bits of the target register.
• Insert—Select a left- or right-justified field of n bits in the source register; insert this field
starting at bit position b of the target register; leave other bits of the target register
unchanged.
• Rotate—Rotate the contents of a register right or left n bits without masking.
Table C-1. Subtract Immediate Simplified Mnemonics
Simplified Mnemonic Standard Mnemonic
subi r D ,r A , value addi r D ,r A , –value
subis r D ,r A , value addis r D ,r A , –value
subic r D ,r A , value addic r D ,r A , –value
subic. r D ,r A , value addic. r D ,r A , –value
Table C-2. Subtract Simplified Mnemonics
Simplified Mnemonic Standard Mnemonic
1
1
r D ,r B ,r A is not the standard order for the operands. The order of r B and r A is
reversed to show the equivalent behavior of the simplified mnemonic.
sub [ o ][ . ] r D ,r A ,r B subf [ o ][ . ] r D ,r B ,r A
subc [ o ][ . ] r D ,r A ,r B subfc [ o ][ . ] r D ,r B ,r A