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From: "pinskia at gcc dot gnu.org" <gcc-bugzilla@gcc.gnu.org>
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Subject: [Bug middle-end/95126] [9/10/11/12 Regression] Missed opportunity to
 turn static variables into immediates
Date: Mon, 13 Dec 2021 04:56:36 +0000
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https://gcc.gnu.org/bugzilla/show_bug.cgi?id=3D95126

Andrew Pinski <pinskia at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
           Keywords|                            |needs-bisection
           Severity|normal                      |enhancement
            Summary|Missed opportunity to turn  |[9/10/11/12 Regression]
                   |static variables into       |Missed opportunity to turn
                   |immediates                  |static variables into
                   |                            |immediates
   Target Milestone|---                         |9.5
      Known to work|                            |5.1.0
      Known to fail|                            |5.2.0

--- Comment #2 from Andrew Pinski <pinskia at gcc dot gnu.org> ---
Hmm, in GCC 5.1.0 (and before) we used to produce:
        mov     rdi, QWORD PTR s.1839[rip]
        jmp     func

In GCC 5.2.0 and above GCC produces:

        movzx   edi, WORD PTR s.1839[rip+2]
        movzx   edx, WORD PTR s.1839[rip]
        sal     rdi, 16
        mov     rax, rdi
        movzx   edi, WORD PTR s.1839[rip+4]
        or      rax, rdx
        sal     rdi, 32
        or      rdi, rax
        jmp     func

In both cases, the expander sees:
  <bb 2>:
  func (s); [tail call]
  return;

But the expander goes bad.
So this has to be a patch which was backported to the GCC 5 branch which ca=
used
to produce even worse code.=