adr

Form PC-relative Address (Thumb)

ADR <Rd>, <label>

Adds an immediate value to the PC (Thumb).

Details

Computes a PC-relative address by adding an 8-bit immediate (shifted left by 2) to the aligned PC and writes the result to a register. No condition flags are affected. This Thumb 16-bit instruction is available in all Thumb-capable processors.

Pseudocode Operation

Rd ← Align(PC, 4) + (imm8 << 2)

Example

ADR r0, label

Encoding

Binary Layout
1010
0
Rd
imm8
 
Format Thumb Data Proc
Opcode 0xA000
Extension T32 (Thumb)

Operands

  • Rd
    Destination general-purpose register
  • label
    Label

Reference (Arm AArch32 ISA)

Instruction Forms

Encoding Instruction ISA Bit pattern
0x028F0000 ADR{<c>}{<q>} <Rd>, <label> A32 cond | 0010 | 100 | 0 | 1111 | Rd | imm12
0x024F0000 ADR{<c>}{<q>} <Rd>, <label> A32 cond | 0010 | 010 | 0 | 1111 | Rd | imm12
0xA000 ADR{<c>}{<q>} <Rd>, <label> T32 1010 | 0 | Rd | imm8
0xF2AF0000 ADR{<c>}{<q>} <Rd>, <label> T32 11110 | i | 10 | 1 | 0 | 1 | 0 | 1111 | 0 | imm3 | Rd | imm8
0xF20F0000 ADR{<c>}.W <Rd>, <label> T32 11110 | i | 10 | 0 | 0 | 0 | 0 | 1111 | 0 | imm3 | Rd | imm8

Description

Form PC-relative address adds an immediate value to the PC value to form a PC-relative address, and writes the result to the destination register.

Operation

if ConditionPassed() then
    EncodingSpecificOperations();
    result = if add then (Align(PC,4) + imm32) else (Align(PC,4) - imm32);
    if d == 15 then          // Can only occur for A32 encodings
        ALUWritePC(result);
    else
        R[d] = result;