[Bug target/87302] New: -mfpu=auto -march=armv8-a does not work

[nsz at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=87302

            Bug ID: 87302
           Summary: -mfpu=auto -march=armv8-a does not work
           Product: gcc
           Version: 8.2.1
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: target
          Assignee: unassigned at gcc dot gnu.org
          Reporter: nsz at gcc dot gnu.org
  Target Milestone: ---

i think the following inconsistency is problematic:

on a hard float toolchain (-mfloat-abi=hard):

$ arm-none-linux-gnueabihf-gcc -mfpu=auto -march=armv7-a a.c ; echo $?
cc1: error: -mfloat-abi=hard: selected processor lacks an FPU
1
$ arm-none-linux-gnueabihf-gcc -mfpu=auto -march=armv7-a+fp a.c ; echo $?
0
$ arm-none-linux-gnueabihf-gcc -mfpu=auto -march=armv8-a a.c ; echo $?
cc1: error: -mfloat-abi=hard: selected processor lacks an FPU
1
$ arm-none-linux-gnueabihf-gcc -mfpu=auto -march=armv8-a+fp a.c ; echo $?
arm-none-linux-gnueabihf-gcc: error: 'armv8-a' does not support feature 'fp'
arm-none-linux-gnueabihf-gcc: note: valid feature names are: crc simd crypto
nocrypto nofp; did you mean 'nofp'?
1
$ arm-none-linux-gnueabihf-gcc -mfpu=auto -march=armv8-a+simd a.c ; echo $?
0

so it seems neither armv8-a nor armv8-a+fp work with -mfpu=auto, but
armv8-a+simd and armv7-a+fp do.