This is a shorthand for the immediate argument being 0, as described here:
https://developer.arm.com/docs/ddi0596/latest/base-instructions-alphabetic-order/ldraa-ldrab-load-register-with-pointer-authentication
This is because the instructions still have a use with an immediate
argument of 0, unlike loads without the PAC functionality. Currently,
the mnemonics are
LDRAA Xt, [Xn, #<simm10>]!
LDRAB Xt, [Xn, #<simm10>]!
After this patch they become
LDRAA Xt, [Xn {, #<simm10>}]!
LDRAB Xt, [Xn {, #<simm10>}]!
gas * config/tc-aarch64.c (parse_address_main): Accept the omission of
the immediate argument for ldraa and ldrab as a shorthand for the
immediate being 0.
* testsuite/gas/aarch64/ldraa-ldrab-no-offset.d: New test.
* testsuite/gas/aarch64/ldraa-ldrab-no-offset.s: New test.
* testsuite/gas/aarch64/illegal-ldraa.s: Modified to accept the
writeback form with no offset.
* testsuite/gas/aarch64/illegal-ldraa.s: Removed missing offset
error.
opcodes * aarch64-opc.c (print_immediate_offset_address): Don't print the
immediate for the writeback form of ldraa/ldrab if it is 0.
* aarch64-tbl.h: Updated the documentation for ADDR_SIMM10.
* aarch64-opc-2.c: Regenerated.
1820262bc9