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From: "rearnsha at gcc dot gnu.org" <gcc-bugzilla@gcc.gnu.org>
To: gcc-bugs@gcc.gnu.org
Subject: [Bug target/100067] New: Unexpected warning for -mcpu=neoverse-n1
 when configured with --with-fpu
Date: Tue, 13 Apr 2021 17:40:43 +0000
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https://gcc.gnu.org/bugzilla/show_bug.cgi?id=3D100067

            Bug ID: 100067
           Summary: Unexpected warning for -mcpu=3Dneoverse-n1 when
                    configured with --with-fpu
           Product: gcc
           Version: 11.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: target
          Assignee: unassigned at gcc dot gnu.org
          Reporter: rearnsha at gcc dot gnu.org
  Target Milestone: ---

If the compiler is configured with (for example):

--with-arch=3Darmv7-a --with-fpu=3Dneon --with-float=3Dhard

then compiling with

gcc -S -mcpu=3Dneoverse-n1 <any-c-file>

leads to an unexpected warning:
cc1: warning: switch =E2=80=98-mcpu=3Dneoverse-n1=E2=80=99 conflicts with =
=E2=80=98-march=3Darmv8.2-a=E2=80=99
switch

The same can be seen if -mfpu is passed explicitly on the command-line (whi=
ch,
while it shouldn't happen, is slightly less surprising).

If -mfpu is specified to be anything other than auto (via command line or
configuration), it is expected that this will override *all* features from =
the
cpu/arch setting that relate to the use of the FPU.

Note, we should probably at this point progress the deprecation process for
-mfpu by deprecating the config option that allows this to be set during
configure.=