i386: Fix up *vec_concat<mode>_0_1 [PR101007]

On Fri, Apr 23, 2021 at 12:53:58PM +0800, Hongtao Liu via Gcc-patches wrote:
> -(define_insn "*vec_concatv4si_0"
> -  [(set (match_operand:V4SI 0 "register_operand"       "=v,x")
> -     (vec_concat:V4SI
> -       (match_operand:V2SI 1 "nonimmediate_operand" "vm,?!*y")
> -       (match_operand:V2SI 2 "const0_operand"       " C,C")))]
> +(define_insn "*vec_concat<mode>_0"
> +  [(set (match_operand:VI124_128 0 "register_operand"       "=v,x")
> +     (vec_concat:VI124_128
> +       (match_operand:<ssehalfvecmode> 1 "nonimmediate_operand" "vm,?!*y")
> +       (match_operand:<ssehalfvecmode> 2 "const0_operand"       " C,C")))]
>    "TARGET_SSE2"
>    "@
>     %vmovq\t{%1, %0|%0, %1}
> @@ -22154,6 +22157,24 @@ (define_insn "avx_vec_concat<mode>"
>     (set_attr "prefix" "maybe_evex")
>     (set_attr "mode" "<sseinsnmode>")])
>
> +(define_insn_and_split "*vec_concat<mode>_0"
> +  [(set (match_operand:V 0 "register_operand")
> +     (vec_select:V
> +       (vec_concat:<ssedoublevecmode>
> +         (match_operand:V 1 "nonimmediate_operand")
> +         (match_operand:V 2 "const0_operand"))
> +       (match_parallel 3 "movq_parallel"
> +         [(match_operand 4 "const_int_operand")])))]
> +  "ix86_pre_reload_split ()"
> +  "#"
> +  "&& 1"
> +  [(set (match_dup 0)
> +     (vec_concat:V (match_dup 1) (match_dup 5)))]
> +{
> +  operands[1] = gen_lowpart (<ssehalfvecmode>mode, operands[1]);
> +  operands[5] = CONST0_RTX (<ssehalfvecmode>mode);
> +})

This regressed the following testcase with -msse -mno-sse2.
The define_insn_and_split splits the permutation into *vec_concat<mode>_0
or *vec_concatv2di_0 insns which both have TARGET_SSE2 in their
conditions (for the former you can see it above), but the
define_insn_and_split matches always when the V mode's condition do,
which for V16QI/V8HI/V4SI/V2DI/V4SF modes is always (well, when those
modes are valid, which is TARGET_SSE).

2021-06-11  Jakub Jelinek  <jakub@redhat.com>

	PR target/101007
	* config/i386/sse.md (*vec_concat<mode>_0_1): Require TARGET_SSE2.

	* gcc.target/i386/sse-pr101007.c: New test.