[Bug target/97327] New: -mcpu=cortex-m55 warns without -mfloat-abi=hard or -march=armv8.1-m.main

[Bug target/97327] New: -mcpu=cortex-m55 warns without -mfloat-abi=hard or -march=armv8.1-m.main

[clyon at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=97327

            Bug ID: 97327
           Summary: -mcpu=cortex-m55 warns without -mfloat-abi=hard or
                    -march=armv8.1-m.main
           Product: gcc
           Version: unknown
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: target
          Assignee: unassigned at gcc dot gnu.org
          Reporter: clyon at gcc dot gnu.org
  Target Milestone: ---

When compiling with
-mthumb -mcpu=cortex-m55
I get:
cc1: warning: switch '-mcpu=cortex-m55' conflicts with '-march=armv8.1-m.main'
switch

unless I add -mfloat-abi=hard
or -march=armv8.1-m.main 
which is a bit counter-intuitive.

[Bug target/97327] -mcpu=cortex-m55 warns without -mfloat-abi=hard or -march=armv8.1-m.main

[clyon at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=97327

Christophe Lyon <clyon at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Target|                            |arm
   Target Milestone|---                         |11.0

[Bug target/97327] -mcpu=cortex-m55 warns without -mfloat-abi=hard or -march=armv8.1-m.main

[clyon at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=97327

--- Comment #1 from Christophe Lyon <clyon at gcc dot gnu.org> ---
Similarly:
-mcpu=cortex-m55+nomve -march=armv8.1-m.main+mve -mfloat-abi=softfp
cc1: warning: switch '-mcpu=cortex-m55' conflicts with '-march=armv8.1-m.main'
switch

-mcpu=cortex-m55+nomve -march=armv8.1-m.main -mfloat-abi=softfp
cc1: warning: switch '-mcpu=cortex-m55' conflicts with '-march=armv8.1-m.main'
switch

[Bug target/97327] -mcpu=cortex-m55 warns without -mfloat-abi=hard or -march=armv8.1-m.main

[jgreenhalgh at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=97327

James Greenhalgh <jgreenhalgh at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
     Ever confirmed|0                           |1
                 CC|                            |jgreenhalgh at gcc dot gnu.org
   Last reconfirmed|                            |2020-10-08
             Status|UNCONFIRMED                 |NEW

[Bug target/97327] -mcpu=cortex-m55 warns without -mfloat-abi=hard or -march=armv8.1-m.main

[sripar01 at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=97327

SRINATH PARVATHANENI <sripar01 at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|NEW                         |ASSIGNED
           Assignee|unassigned at gcc dot gnu.org      |sripar01 at gcc dot gnu.org

[Bug target/97327] -mcpu=cortex-m55 warns without -mfloat-abi=hard or -march=armv8.1-m.main

[avieira at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=97327

avieira at gcc dot gnu.org changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |avieira at gcc dot gnu.org

--- Comment #2 from avieira at gcc dot gnu.org ---
The last two should conflict though right? I never quite understood this
warning to be fair. My personal preference would be to warn for any invocation
where both -mcpu and -march are passed, but I understand that for legacy
reasons that might be undesirable.

Though yeah -mcpu=cortex-m55 with a -mfloat-abi=soft should not warn for
anything obviously.

[Bug target/97327] -mcpu=cortex-m55 warns without -mfloat-abi=hard or -march=armv8.1-m.main

[clyon at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=97327

--- Comment #3 from Christophe Lyon <clyon at gcc dot gnu.org> ---
Well, why does the warning remove the extensions? (+XXXX) It seems to indicate
they are not taken into account, which is confusing: it doesn't really say why
there is a conflict.

Why do you think -mcpu=cortex-m55+nomve -march=armv8.1-m.main should conflict?
It's not clear to me when I look at arm-cpus.in

[Bug target/97327] -mcpu=cortex-m55 warns without -mfloat-abi=hard or -march=armv8.1-m.main

[avieira at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=97327

--- Comment #4 from avieira at gcc dot gnu.org ---
With -mcpu=cortex-m55+nomve should be equivalent to -march=armv8.1-m.main+dsp

[Bug target/97327] -mcpu=cortex-m55 warns without -mfloat-abi=hard or -march=armv8.1-m.main

[avieira at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=97327

--- Comment #5 from avieira at gcc dot gnu.org ---
Your other one:
-mcpu=cortex-m55+nomve -march=armv8.1-m.main+mve -mfloat-abi=softfp
This has cpu without mve and arch with mve.

Another fun caveat to look at is in:
-mcpu=cortex-m55 -mfloat-abi=soft
float-abi=soft disables vector instructions, so it makes sense to remove mve.fp
and fp.dp/fp. However, we must make sure that +mve is still passed to the
assembler because +mve enables new scalar shift instructions.

If we want to be in-sync with legacy though I don't think we even need to look
at all these complicated cases as. Since it seems in the past we ignore fp
extensions, take for instance:
arm-none-eabi-gcc -mcpu=cortex-m7 -march=armv7e-m -mfloat-abi=hard
arm-none-eabi-gcc -mcpu=cortex-m7 -march=armv7e-m+fp -mfloat-abi=hard 
arm-none-eabi-gcc -mcpu=cortex-m7+nofp -march=armv7e-m  -mfloat-abi=soft
arm-none-eabi-gcc -mcpu=cortex-m7+nofp -march=armv7e-m+fp

None of these give the warning, so maybe the solution is to ignore MVE as well
as the FP extension when checking for this? There is a bit in the warning code 
that says:
          /* And if the target ISA lacks floating point, ignore any
             extensions that depend on that.  */
          if (!bitmap_bit_p (target->isa, isa_bit_vfpv2))
            bitmap_and_compl (isa_delta, isa_delta, isa_all_fpbits);

Maybe we need to 'ignore any extension that depends on mve'? But I don't quite
understand how this works with the case where we do have isa_bit_vfpv2...

For Srinath's sake it would be good to agree on what the behaviour should be
and then work towards that. I personally don't have a strong feeling about this
other then: passing '-mcpu=cortex-m55' shouldn't give warnings ... since well
that's insane :P

[Bug target/97327] -mcpu=cortex-m55 warns without -mfloat-abi=hard or -march=armv8.1-m.main

[cvs-commit at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=97327

--- Comment #6 from CVS Commits <cvs-commit at gcc dot gnu.org> ---
The master branch has been updated by SRINATH PARVATHANENI
<sripar01@gcc.gnu.org>:

https://gcc.gnu.org/g:90042c43a92c452a5f9f3afbfcdad511ea09a54f

commit r11-4006-g90042c43a92c452a5f9f3afbfcdad511ea09a54f
Author: Srinath Parvathaneni <srinath.parvathaneni@arm.com>
Date:   Fri Oct 16 14:53:28 2020 +0100

    arm: Fix the warning -mcpu=cortex-m55 conflicting with
-march=armv8.1-m.main (pr97327).

    This patch fixes (PR97327) the warning -mcpu=cortex-m55 conflicts with
-march=armv8.1-m.main
    for -mfloat-abi=soft by adding the isa_bit_mve_float to clearing FP bit
list.

    The following combination are fixed with this patch:
    $ cat bug.c
    int main(){
    return 0;
    }

    $ arm-none-eabi-gcc -mcpu=cortex-m55 -mfloat-abi=soft bug.c -c
    $ arm-none-eabi-gcc -mcpu=cortex-m55 -mfloat-abi=soft
-march=armv8.1-m.main+mve bug.c -c

    Before this patch for above combinations:
    cc1: warning: switch '-mcpu=cortex-m55' conflicts with
'-march=armv8.1-m.main' switch

    After this patch for above combinations no warning/errors.

    gcc/ChangeLog:

    2020-10-16  Srinath Parvathaneni  <srinath.parvathaneni@arm.com>

            PR target/97327
            * config/arm/arm.c (fp_bitlist): Add isa_bit_mve_float to FP bits
array.

    gcc/testsuite/ChangeLog:

            PR target/97327
            * gcc.target/arm/mve/intrinsics/pr97327.c: New test.

[Bug target/97327] -mcpu=cortex-m55 warns without -mfloat-abi=hard or -march=armv8.1-m.main

[cvs-commit at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=97327

--- Comment #7 from CVS Commits <cvs-commit at gcc dot gnu.org> ---
The releases/gcc-10 branch has been updated by SRINATH PARVATHANENI
<sripar01@gcc.gnu.org>:

https://gcc.gnu.org/g:634ee90804cae1e08c8e25913288e0ecf0a5ea0a

commit r10-8911-g634ee90804cae1e08c8e25913288e0ecf0a5ea0a
Author: Srinath Parvathaneni <srinath.parvathaneni@arm.com>
Date:   Fri Oct 16 14:53:28 2020 +0100

    arm: Fix the warning -mcpu=cortex-m55 conflicting with
-march=armv8.1-m.main (pr97327).

    This patch fixes (PR97327) the warning -mcpu=cortex-m55 conflicts with
-march=armv8.1-m.main
    for -mfloat-abi=soft by adding the isa_bit_mve_float to clearing FP bit
list.

    The following combination are fixed with this patch:
    $ cat bug.c
    int main(){
    return 0;
    }

    $ arm-none-eabi-gcc -mcpu=cortex-m55 -mfloat-abi=soft bug.c -c
    $ arm-none-eabi-gcc -mcpu=cortex-m55 -mfloat-abi=soft
-march=armv8.1-m.main+mve bug.c -c

    Before this patch for above combinations:
    cc1: warning: switch '-mcpu=cortex-m55' conflicts with
'-march=armv8.1-m.main' switch

    After this patch for above combinations no warning/errors.

    gcc/ChangeLog:

    2020-10-16  Srinath Parvathaneni  <srinath.parvathaneni@arm.com>

            PR target/97327
            * config/arm/arm.c (fp_bitlist): Add isa_bit_mve_float to FP bits
array.

    gcc/testsuite/ChangeLog:

            PR target/97327
            * gcc.target/arm/mve/intrinsics/pr97327.c: New test.

    (cherry picked from commit 90042c43a92c452a5f9f3afbfcdad511ea09a54f)

[Bug target/97327] -mcpu=cortex-m55 warns without -mfloat-abi=hard or -march=armv8.1-m.main

[sripar01 at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=97327

SRINATH PARVATHANENI <sripar01 at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|ASSIGNED                    |RESOLVED
         Resolution|---                         |FIXED

--- Comment #8 from SRINATH PARVATHANENI <sripar01 at gcc dot gnu.org> ---
Committed patches to trunk and GCC-10 branches.