If I build TF-A 2.4 with clang 12 for corstone500 (aarch32, cortex-A5) it fails in the assembler:
a5ds/debug/bl1/bl1_entrypoint.o] Error 1
:2: error: use of SP in the list is deprecated
ldm r1!, {sp, lr}
^
bl1/aarch32/bl1_exceptions.S:156:2: note: while in macro instantiation
monitor_exit
^
<instantiation>:40:2: error: use of SP in the list is deprecated
ldm r1!, {r2, sp, lr}
^
bl1/aarch32/bl1_exceptions.S:156:2: note: while in macro instantiation
monitor_exit
^
<instantiation>:44:2: error: use of SP in the list is deprecated
ldm r1!, {r2, sp, lr}
^
bl1/aarch32/bl1_exceptions.S:156:2: note: while in macro instantiation
monitor_exit
^
<instantiation>:48:2: error: use of SP in the list is deprecated
ldm r1!, {r2, sp, lr}
^
bl1/aarch32/bl1_exceptions.S:156:2: note: while in macro instantiation
monitor_exit
^
<instantiation>:52:2: error: use of SP in the list is deprecated
ldm r1!, {r2, sp, lr}
^
bl1/aarch32/bl1_exceptions.S:156:2: note: while in macro instantiation
monitor_exit
^
<instantiation>:56:2: error: use of SP in the list is deprecated
ldm r1!, {r2, sp, lr}
^
bl1/aarch32/bl1_exceptions.S:156:2: note: while in macro instantiation
monitor_exit
^