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ARM Compiler armasm User Guide : LDP

LDP

Load Pair of Registers.

Syntax

LDP Wt1, Wt2, [Xn|SP], #imm ; 32-bit general registers, Post-index

LDP Xt1, Xt2, [Xn|SP], #imm ; 64-bit general registers, Post-index

LDP Wt1, Wt2, [Xn|SP, #imm]! ; 32-bit general registers, Pre-index

LDP Xt1, Xt2, [Xn|SP, #imm]! ; 64-bit general registers, Pre-index

LDP Wt1, Wt2, [Xn|SP{, #imm}] ; 32-bit general registers, Signed offset

LDP Xt1, Xt2, [Xn|SP{, #imm}] ; 64-bit general registers, Signed offset

Where:

Wt1

Is the 32-bit name of the first general-purpose register to be transferred.

Wt2

Is the 32-bit name of the second general-purpose register to be transferred.

imm

Depends on the instruction variant:

32-bit general registers

Is the signed immediate byte offset, a multiple of 4 in the range -256 to 252.

64-bit general registers

Is the signed immediate byte offset, a multiple of 8 in the range -512 to 504.

Xt1

Is the 64-bit name of the first general-purpose register to be transferred.

Xt2

Is the 64-bit name of the second general-purpose register to be transferred.

Xn|SP

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

Usage

Load Pair of Registers calculates an address from a base register value and an immediate offset, loads two 32-bit words or two 64-bit doublewords from memory, and writes them to two registers. For information about memory accesses, see Load/Store addressing modes in the ARMv8-A Architecture Reference Manual.

Note

For information about the CONSTRAINED UNPREDICTABLE behavior of this instruction, see Architectural Constraints on UNPREDICTABLE behaviors in the ARMv8-A Architecture Reference Manual, and particularly LDP in the ARMv8-A Architecture Reference Manual.
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