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From: "ktkachov at gcc dot gnu.org" <gcc-bugzilla@gcc.gnu.org>
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Subject: [Bug target/106583] New: Suboptimal immediate generation on aarch64
Date: Thu, 11 Aug 2022 09:01:33 +0000
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https://gcc.gnu.org/bugzilla/show_bug.cgi?id=3D106583

            Bug ID: 106583
           Summary: Suboptimal immediate generation on aarch64
           Product: gcc
           Version: unknown
            Status: UNCONFIRMED
          Keywords: missed-optimization
          Severity: normal
          Priority: P3
         Component: target
          Assignee: unassigned at gcc dot gnu.org
          Reporter: ktkachov at gcc dot gnu.org
  Target Milestone: ---
            Target: aarch64

A simple codegen issue:
unsigned long long
foo (void)
{
  return 0x7efefefefefefeff;
}

generates at -O2
foo:
        mov     x0, 65279
        movk    x0, 0xfefe, lsl 16
        movk    x0, 0xfefe, lsl 32
        movk    x0, 0x7efe, lsl 48
        ret

whereas LLVM can do:
foo:                                    // @foo
        mov     x0, #-72340172838076674
        movk    x0, #65279
        movk    x0, #32510, lsl #48
        ret

Should be a matter of just making aarch64_internal_mov_immediate in aarch64=
.cc
a bit smarter=