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From: "iains at gcc dot gnu.org" <gcc-bugzilla@gcc.gnu.org>
To: gcc-bugs@gcc.gnu.org
Subject: [Bug target/111876] New: aarch64: Wrong code for bf16 complex
 mul/div when the target has +fp16 support.
Date: Thu, 19 Oct 2023 09:36:16 +0000
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https://gcc.gnu.org/bugzilla/show_bug.cgi?id=3D111876

            Bug ID: 111876
           Summary: aarch64: Wrong code for bf16 complex mul/div when the
                    target has +fp16 support.
           Product: gcc
           Version: 14.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: target
          Assignee: unassigned at gcc dot gnu.org
          Reporter: iains at gcc dot gnu.org
  Target Milestone: ---

this is somewhat similar to PR111867, but in this case the issue seems to
happen at expand time.

---- reduced from "bfloat16-complex.c"

volatile __bf16 a =3D 1.0bf16;
typedef _Complex float __cbf16 __attribute__((__mode__(__BC__)));
volatile __cbf16 b =3D __builtin_complex (2.0bf16, 3.0bf16);

int main (void)
{
  volatile __cbf16 r ;
  r =3D a + b;
  r *=3D r;
  return 0;
}

----

For -march=3Darmv8.4-a+fp16

This lowers to calls to (non-existent libgcc) ___mulbc3 (and __divbc3, when
division is included).

For -march=3Darmv8.4-a

This promotes the bf16 -> float and calls __mulsc3 (which exists)=