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From: "acoplan at gcc dot gnu.org" <gcc-bugzilla@gcc.gnu.org>
To: gcc-bugs@gcc.gnu.org
Subject: [Bug target/113089] [14 Regression][aarch64] ICE in
 process_uses_of_deleted_def, at rtl-ssa/changes.cc:252 since
 r14-6605-gc0911c6b357ba9
Date: Wed, 20 Dec 2023 12:08:08 +0000
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https://gcc.gnu.org/bugzilla/show_bug.cgi?id=3D113089

--- Comment #10 from Alex Coplan <acoplan at gcc dot gnu.org> ---
So we have this RTL going into ldp_fusion2:

  103: x16:DI=3D[x15:DI--]
      REG_INC x15:DI
  104: x16:SI=3Dzero_extend([x16:DI])
  105: x16:SI=3Dx11:SI-x16:SI
  106: x16:SI=3Dx8:SI*x16:SI+x16:SI
 1117: {x26:DI=3Dunspec[[x10:DI-0x30]] 39;x27:DI=3Dunspec[[x10:DI-0x30]] 40=
;}
 1118: x27:SI=3Dzero_extend([x27:DI])
 1119: x27:SI=3Dx11:SI-x27:SI
 1048: x20:DI=3D[x10:DI-0x10]
      REG_EQUIV [x10:DI-0x10]
 1049: x20:SI=3Dzero_extend([x20:DI])
 1050: x20:SI=3Dx11:SI-x20:SI
 1367: debug D#22 =3D> x15:DI
 1025: x15:DI=3D[x15:DI]

and we try to fuse (103,1025):

fusing pair [L=3D1] (103,1025), base=3D15, hazards: (104,103), move_range:
(103,103)
  ldp: i103 has wb but subsequent i1025 has non-wb update of base (r15),
dropping wb

but we fail to update the debug insn 1367 which has a use of the def of x15=
 in
i103 that we're deleting.=