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From: "olegendo at gcc dot gnu.org" <gcc-bugzilla@gcc.gnu.org>
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Subject: [Bug target/65151] [SH][4.9 Regression] Internal compiler error when trying to build libav 11.2 on sh4
Date: Sat, 21 Feb 2015 23:09:00 -0000
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https://gcc.gnu.org/bugzilla/show_bug.cgi?id=65151

--- Comment #6 from Oleg Endo <olegendo at gcc dot gnu.org> ---
(In reply to Oleg Endo from comment #5)
> The problem is the following insn:
> 
> (insn 45 11 12 2 (set (reg:HI 168 [ x ])
>         (subreg/s/u:HI (reg:SI 147 t) 0)) cchMsw9Z.out:9 -1
>      (expr_list:REG_DEAD (reg:SI 147 t)
>         (nil)))
> 
> which is not in sh.md.
> The insn is created by the asmcons pass.

More precisely, it's 'emit_move_insn' in gcc/function.c in function
match_asm_constraints_1 at line 7152.
BTW, the test case from attachment 34825 also fails at -O1, -O2 and -Os.


On current trunk (GCC 5), the problem doesn't happen due to the treg_set_expr
stuff that has been recently added, it seems.

After combine, the insns are:

(insn 11 8 12 2 (parallel [
            (set (reg/v:SI 163 [ x ])
                (eq:SI (reg:SI 6 r6 [ bits_per_component ])
                    (const_int 10 [0xa])))
            (clobber (reg:SI 147 t))
        ]) 410 {any_treg_expr_to_reg}
     (expr_list:REG_UNUSED (reg:SI 147 t)
        (expr_list:REG_DEAD (reg:SI 6 r6 [ bits_per_component ])
            (nil))))
(insn 12 11 13 2 (set (reg:HI 170 [ x ])
        (asm_operands:HI ("swap.b %0,%0") ("=r") 0 [
                (subreg/s/v:HI (reg/v:SI 163 [ x ]) 0)
            ]
             [
                (asm_input:HI ("0") cchMsw9Z.out:8)
            ]
             [] cchMsw9Z.out:8)) cchMsw9Z.out:8 -1
     (expr_list:REG_DEAD (reg/v:SI 163 [ x ])
        (nil)))

Which is then converted by the treg_set_expr splitter code during the split1
pass into:

(insn 52 8 53 2 (set (reg:SI 147 t)
        (eq:SI (reg:SI 6 r6 [ bits_per_component ])
            (const_int 10 [0xa]))) -1
     (nil))
(insn 53 52 12 2 (set (reg/v:SI 163 [ x ])
        (reg:SI 147 t)) -1
     (expr_list:REG_UNUSED (reg:SI 147 t)
        (nil)))
(insn 12 53 13 2 (set (reg:HI 170 [ x ])
        (asm_operands:HI ("swap.b %0,%0") ("=r") 0 [
                (subreg/s/v:HI (reg/v:SI 163 [ x ]) 0)
            ]
             [
                (asm_input:HI ("0") cchMsw9Z.out:8)
            ]
             [] cchMsw9Z.out:8)) cchMsw9Z.out:8 -1
     (expr_list:REG_DEAD (reg/v:SI 163 [ x ])
        (nil)))

In asmcons, emit_move_insn then adds the following insn:

(insn 58 53 12 2 (set (reg:HI 170 [ x ])
        (subreg/s/v:HI (reg/v:SI 163 [ x ]) 0)) cchMsw9Z.out:8 -1
     (nil))

from there on everything works out.