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SUBS (extended register)

Subtract (extended register), setting flags.

This instruction is used by the alias CMP (extended register).

Syntax

SUBS Wd, Wn|WSP, Wm{, extend {#amount}} ; 32-bit general registers

SUBS Xd, Xn|SP, Rm{, extend {#amount}} ; 64-bit general registers

Where:

Wd

Is the 32-bit name of the general-purpose destination register.

Wn|WSP

Is the 32-bit name of the first source general-purpose register or stack pointer.

Wm

Is the 32-bit name of the second general-purpose source register.

extend

Is the extension to be applied to the second source operand:

32-bit general registers

Can be one of UXTB, UXTH, LSL|UXTW, UXTX, SXTB, SXTH, SXTW or SXTX.

If Rn is WSP then LSL is preferred rather than UXTW, and can be omitted when amount is 0. In all other cases extend is required and must be UXTW rather than LSL.

64-bit general registers

Can be one of UXTB, UXTH, UXTW, LSL|UXTX, SXTB, SXTH, SXTW or SXTX.

If Rn is SP then LSL is preferred rather than UXTX, and can be omitted when amount is 0. In all other cases extend is required and must be UXTX rather than LSL.

Xd

Is the 64-bit name of the general-purpose destination register.

Xn|SP

Is the 64-bit name of the first source general-purpose register or stack pointer.

R

Is a width specifier, and can be either W or X.

m

Is the number [0-30] of the second general-purpose source register or the name ZR (31).

amount

Is the left shift amount to be applied after extension in the range 0 to 4, defaulting to 0. It must be absent when extend is absent, is required when extend is LSL, and is optional when extend is present but not LSL.

Usage

The following table shows the valid specifier combinations:

Table 16-7 SUBS (64-bit general registers) specifier combinations

R extend
W SXTB
W SXTH
W SXTW
W UXTB
W UXTH
W UXTW
X LSL|UXTX
X SXTX
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