aarch64: add PAuth_LR instructions with imm16 operand
Adds immediate PC-relative forms (AUTIA<k>SPPC, RETA<k>SPPC) for AArch64 PAuth_LR instructions using a 16-bit offset.
This patch implements the immediate PC-relative variants of AArch64 FEAT_PAuth_LR instructions: AUTIA<k>SPPC and RETA<k>SPPC. These instructions utilize an unsigned 16-bit offset, scaled by 4, to determine a PC-relative address. The patch introduces a new operand type ADDR_UPCREL16 and handles it as an assembler-internal fixup within gas, as no object-file relocation is required. It also updates disassembly to correctly compute target addresses and adds corresponding gas tests.
In Details
This patch adds support for immediate, PC-relative addressing modes for AArch64 PAuth_LR instructions, specifically AUTIA<k>SPPC and RETA<k>SPPC. These instructions use a 16-bit unsigned immediate value, which is scaled by 4, to calculate a target address relative to the current Program Counter (PC). The patch introduces ADDR_UPCREL16 as a new operand type in gas/config/tc-aarch64.c and modifies opcodes/aarch64-opc.c and opcodes/aarch64-tbl.h to handle the encoding and decoding. Crucially, this offset is resolved internally by gas as a fixup, meaning no relocation information is…
- FEAT_PAuth_LR
- A specific AArch64 hardware feature extension for Pointer Authentication of the Link Register.
- PC-relative address
- An address calculated relative to the current value of the Program Counter (PC). This allows instructions to refer to nearby code or data without needing absolute addresses.
- imm16
- A 16-bit immediate value. This refers to a constant value embedded directly within an instruction.
- gas
- The GNU Assembler, part of the binutils package. It translates assembly language code into machine code.
- assembler-internal fixup
- A mechanism within an assembler to resolve addresses or other values that are not fully known at the time of initial assembly. The assembler performs these calculations internally before generating the final machine code.
- relocation
- Information emitted into an object file that tells the linker how to modify addresses in the code or data sections when the code is moved to a different memory location.