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From: "tnfchris at gcc dot gnu.org" <gcc-bugzilla@gcc.gnu.org>
To: gcc-bugs@gcc.gnu.org
Subject: [Bug target/94396] New: [8/9/10 Regression] fp16 feature bits not
 passed on to assembler from Armv8.4-a and up.
Date: Mon, 30 Mar 2020 07:04:26 +0000
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https://gcc.gnu.org/bugzilla/show_bug.cgi?id=3D94396

            Bug ID: 94396
           Summary: [8/9/10 Regression] fp16 feature bits not passed on to
                    assembler from Armv8.4-a and up.
           Product: gcc
           Version: 10.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: target
          Assignee: tnfchris at gcc dot gnu.org
          Reporter: tnfchris at gcc dot gnu.org
  Target Milestone: ---
            Target: aarch64-*

At Arm8.2-a using `+fp16fml` enables both `+fp` and `+fp16` as such the
smallest canonical option to use is `armv8.2-a+fp16fml`.

For `Armv8.4-a` and up `+fp16fml` is mandatory if `+fp16` but optional
otherwise. This requirement confuses the canonization.

This confusion makes `armv8.4-a+fp16` canonicalize to `armv8.4-a` which is
incorrect and so it's impossible to use `fp16` and `fp16fml` at `armv8.4-a`=
 and
higher.=