ARM 学习笔记之4： 常用指令3) UXTH

UXTH
             Zero extend Halfword.
Syntax
             UXTH{cond} {Rd}, Rm {,rotation}
where:
cond
             is an optional condition code.
Rd
             is the destination register.
Rm
             is the register holding the value to extend.
rotation
             is one of:
                       ROR #8
                                     Value from Rm is rotated right 8 bits.
                       ROR #16
                                    Value from Rm is rotated right 16 bits.
                      ROR #24
                                    Value from Rm is rotated right 24 bits.
                     If rotation is omitted, no rotation is performed.

Operation
UXTH extends a 16-bit value to a 32-bit value. It does this by:
1. Rotating the value from Rm right by 0, 8, 16, or 24 bits.
2. Extracting bits[15:0] from the value obtained.
3. Zero extending to 32 bits.