Hi,

FP instructions are only enabled for TARGET_32BIT and TARGET_HARD_FLOAT
but GCC only gives an error when TARGET_HARD_FLOAT is true and -mfpu is
not set. Among other things, it makes some of the cmse tests (eg.
gcc.target/arm/cmse/baseline/softfp.c) fail when targeting
-march=armv8-m.base -mfpu=<something> -mfloat-abi=softfp. This patch
errors out when a Thumb-1 -like target is selected and a FPU is
specified, thus making such tests being skipped.

ChangeLog entries are as follows:

*** gcc/ChangeLog ***

2018-11-28  thomas Preud'homme  <thomas.preudhomme@linaro.org>

    * config/arm/arm.c (arm_options_perform_arch_sanity_checks): Error out
    if targeting Thumb-1 with an FPU specified.

*** gcc/testsuite/ChangeLog ***

2018-11-28  thomas Preud'homme  <thomas.preudhomme@linaro.org>

    * gcc.target/arm/thumb1_mfpu-1.c: New testcase.
    * gcc.target/arm/thumb1_mfpu-2.c: Likewise.

Testing: No testsuite regression when targeting arm-none-eabi Armv6S-M.
Fails as expected when targeting Armv6-M with an -mfpu or a default FPU.
Succeeds without.

Is this ok for stage3?

Best regards,

Thomas