ecog: Return 1 from insn_invalid_p if REG_INC reg overlaps some stored reg [PR103775]

The following testcase ICEs on aarch64-linux with -g and
assembles with a warning otherwise, because it emits
ldrb w0,[x0,16]!
instruction which sets the x0 register multiple times.
Due to disabled DCE (from -Og) we end up before REE with:
(insn 12 39 13 2 (set (reg:SI 1 x1 [orig:93 _2 ] [93])
        (zero_extend:SI (mem/c:QI (pre_modify:DI (reg/f:DI 0 x0 [114])
                    (plus:DI (reg/f:DI 0 x0 [114])
                        (const_int 16 [0x10]))) [1 u128_1+0 S1 A128]))) "pr103775.c":5:35 117 {*zero_extendqisi2_aarch64}
     (expr_list:REG_INC (reg/f:DI 0 x0 [114])
        (nil)))
(insn 13 12 14 2 (set (reg:DI 0 x0 [orig:112 _2 ] [112])
        (zero_extend:DI (reg:SI 1 x1 [orig:93 _2 ] [93]))) "pr103775.c":5:16 111 {*zero_extendsidi2_aarch64}
     (nil))
which is valid but not exactly efficient as x0 is dead after the
insn that auto-increments it.  REE turns it into:
(insn 12 39 44 2 (set (reg:DI 0 x0)
        (zero_extend:DI (mem/c:QI (pre_modify:DI (reg/f:DI 0 x0 [114])
                    (plus:DI (reg/f:DI 0 x0 [114])
                        (const_int 16 [0x10]))) [1 u128_1+0 S1 A128]))) "pr103775.c":5:35 119 {*zero_extendqidi2_aarch64}
     (expr_list:REG_INC (reg/f:DI 0 x0 [114])
        (nil)))
(insn 44 12 14 2 (set (reg:DI 1 x1)
        (reg:DI 0 x0)) "pr103775.c":5:35 -1
     (nil))
which is invalid because it sets x0 multiple times, one
in SET_DEST of the PATTERN and once in PRE_MODIFY.
As perhaps other passes than REE might suffer from it, IMHO it is better
to reject this during change validation.

2022-03-26  Jakub Jelinek  <jakub@redhat.com>

	PR rtl-optimization/103775
	* recog.cc (check_invalid_inc_dec): New function.
	(insn_invalid_p): Return 1 if REG_INC operand overlaps
	any stored REGs.

	* gcc.dg/pr103775.c: New test.

0 files changed, 0 insertions, 0 deletions