[Bug rtl-optimization/70030] New: [LRA]ICE when reload insn with output scratch operand

[renlin at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=70030

            Bug ID: 70030
           Summary: [LRA]ICE when reload insn with output scratch operand
           Product: gcc
           Version: unknown
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: rtl-optimization
          Assignee: unassigned at gcc dot gnu.org
          Reporter: renlin at gcc dot gnu.org
  Target Milestone: ---

The ICE is triggered when building linux toolchain with local change to gcc
aarch64 backend.

vfprintf.c: In function ‘_IO_vfwprintf’:
vfprintf.c:1689:1: internal compiler error: in lra_set_insn_recog_data, at
lra.c:964
 }
 ^
0x952998 lra_set_insn_recog_data(rtx_insn*)
        src/gcc/gcc/lra.c:962
0x9537b6 lra_get_insn_recog_data
        src/gcc/gcc/lra-int.h:486
0x9537b6 lra_update_insn_regno_info
        src/gcc/gcc/lra.c:1584
0x9537b6 lra_update_insn_regno_info
        src/gcc/gcc/lra.c:1574
0x953a82 lra_push_insn_1
        src/gcc/gcc/lra.c:1649
0x953a82 lra_push_insn(rtx_insn*)
        src/gcc/gcc/lra.c:1657
0x953cb7 push_insns
        gcc/gcc/lra.c:1700
0x954191 lra_process_new_insns(rtx_insn*, rtx_insn*, rtx_insn*, char const*)
        gcc/gcc/lra.c:1754
0x9670e5 curr_insn_transform
        src/gcc/gcc/lra-constraints.c:3962
0x968866 lra_constraints(bool)
        src/gcc/gcc/lra-constraints.c:4450
0x954cb2 lra(_IO_FILE*)
        src/gcc/gcc/lra.c:2277
0x90cfa9 do_reload
        src/gcc/gcc/ira.c:5395
0x90cfa9 execute
        src/gcc/gcc/ira.c:5566

Please submit a full bug report,
with preprocessed source if appropriate.
Please include the complete backtrace with any bug report.
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The situation is like this,
To make insn_1 strict, lra generates a new insn_1_reload insn.
In insn_1_reload, there is a scratch operand with this form
clobber (match_scratch:MODE x "=r")
It's written in this way to reserve a pseudo register which will
be used as temporary within the pattern. 

When lra tries to reload insn_1_reload in later iteration, a new pseudo
register (let say RXX) is created to replace this scratch operand in-place.
Additionally, a new insn will be generated and inserted after insn_1_reload to
finish the reload. It's in this form:
(set scratch, RXX)
And this instruction is illegal. no target implements this kind of pattern.
LRA will ICE because of this. 


(1)       if (get_reload_reg (type, mode, old, goal_alt[i],
                              loc != curr_id->operand_loc[i], "", &new_reg)
              && type != OP_OUT)
            {
              push_to_sequence (before);
              lra_emit_move (new_reg, old);
              before = get_insns ();
              end_sequence ();
            }
(2)       *loc = new_reg;
          if (type != OP_IN
              && find_reg_note (curr_insn, REG_UNUSED, old) == NULL_RTX)
            {
              start_sequence ();
(3）           lra_emit_move (type == OP_INOUT ? copy_rtx (old) : old, new_reg);
              emit_insn (after);
              after = get_insns ();
              end_sequence ();
              *loc = new_reg;
            }

(1) a reload pseudo register is generated: RXX
(2) replace original operand in-place: (clobber RXX)
(3) insert insn to set output operand: (set scratch, RXX)