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From: "jakub at gcc dot gnu.org" <gcc-bugzilla@gcc.gnu.org>
To: gcc-bugs@gcc.gnu.org
Subject: [Bug rtl-optimization/98603] aarch64: ICE in extract_insn (ira) on
 asm goto with bad constraint
Date: Fri, 08 Jan 2021 14:19:53 +0000
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https://gcc.gnu.org/bugzilla/show_bug.cgi?id=3D98603

Jakub Jelinek <jakub at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |jakub at gcc dot gnu.org,
                   |                            |vmakarov at gcc dot gnu.org

--- Comment #1 from Jakub Jelinek <jakub at gcc dot gnu.org> ---
The bug is function.c (instantiate_virtual_regs_in_insn):
      if (!check_asm_operands (PATTERN (insn)))
        {
          error_for_asm (insn, "impossible constraint in %<asm%>");
          /* For asm goto, instead of fixing up all the edges
             just clear the template and clear input operands
             (asm goto doesn't have any output operands).  */
          if (JUMP_P (insn))
            {
              rtx asm_op =3D extract_asm_operands (PATTERN (insn));
              ASM_OPERANDS_TEMPLATE (asm_op) =3D ggc_strdup ("");
              ASM_OPERANDS_INPUT_VEC (asm_op) =3D rtvec_alloc (0);
              ASM_OPERANDS_INPUT_CONSTRAINT_VEC (asm_op) =3D rtvec_alloc (0=
);
            }
          else
            delete_insn (insn);
        }
As the comment documents, that was correct before support for outputs in asm
goto has been added, but for asm insn with outputs, there are multiple
problems.
One is that extract_asm_operands extracts just one of the ASM_OPERANDS, but
with multiple outputs there can be several, and those need to be handled in
sync.
And the other is that we still keep the incorrectly constrained outputs if =
any
in the IL.=