[testsuite] Effective-target depending on current compiler flags?

[Christophe Lyon <christophe.lyon@linaro.org>]

Hi,

While looking at GCC validation results when configured for ARM
cortex-m33 by default, I noticed that
FAIL: gcc.target/arm/cmse/mainline/soft/cmse-5.c  -march=armv8-m.main
-mthumb -mfloat-abi=soft  -O0   scan-assembler msr\tAPSR_nzcvqg, lr

The corresponding line in the testcase is (are):
/* { dg-final { scan-assembler "msr\tAPSR_nzcvq, lr" { target { !
arm_dsp } } } } */
/* { dg-final { scan-assembler "msr\tAPSR_nzcvqg, lr" { target arm_dsp } } } */

So the arm_dsp effective target is true and the test tries to match
APSR_nzcvqg, while APSR_nzcvq is generated, as expected.

There is an inconsistency because the testcase is compiled with
-march=armv8-m.main, while arm_dsp is not: like most effective
targets, it does not take the current cflags into account.
In the present case, the -march flag is added by cmse.exp in the
arguments to gcc-dg-runtest.

I tried to add [current_compiler_flags] to all arm effective targets
(for consistency, it wouldn't make sense to add it to arm_dsp only),
but then I noticed further problems...

For instance, in my configuration, when advsimd-intrinsics.exp is
executed, it tries
check_effective_target_arm_v8_2a_fp16_neon_hw
which fails, and then tries check_effective_target_arm_neon_fp16_ok
which succeeds and thus adds -mfloat-abi=softfp -mfp16-format=ieee to
additional_flags.

Since $additional_flags is passed to gcc-dg-runtest, these flags are
visible by current_compiler_flags and taken into account when
computing effective_targets (since I modified them).

So... when computing arm_v8_2a_fp16_scalar_ok, it uses
-mfloat-abi=softfp -mfp16-format=ieee and doesn't need to add any flag
beyond -march=armv8.2-a+fp16.
So et_arm_v8_2a_fp16_scalar_flags contains -march=armv8.2-a+fp16 only.

Later on, while executing arm.exp, -mfloat-abi=softfp
-mfp16-format=ieee are not part of $DEFAULT_CFLAGS as used by
dg-runtest, but et_arm_v8_2a_fp16_scalar_flags is still in the cache
and it's not valid anymore.

So..... before burying myself, is there already a way to make
effective-targets take the current compiler flags into account as
needed in gcc.target/arm/cmse/mainline/soft/cmse-5.c ?

Not sure my explanation is clear enough :-)

Thanks,

Christophe