[aarch64] Use op_mode instead of vmode for op0, op1 in aarch64_vectorize_vec_perm_const

Hi,
For following test case:

svint32_t foo()
{
  int32x4_t v = (int32x4_t) { 1, 2, 3, 4 };
  svint32_t v2 = svld1rq_s32 (svptrue_b8(), &v[0]);
  return v2;
}

After applying workaround in forwprop to not simplify VEC_PERM_EXPR in
simplify_permutation to avoid type error in middle end (or using
-fno-tree-forwprop)
as mentioned in:
https://gcc.gnu.org/pipermail/gcc-patches/2022-July/598390.html

We get following optimized gimple:
  v2_2 = VEC_PERM_EXPR <{ 1, 2, 3, 4 }, { 1, 2, 3, 4 }, { 0, 1, 2, 3, ... }>;
  return v2_2;

However we hit the following ICE during expansion of vec_perm_expr
because in aarch64_vectorize_vec_perm_const,
op0 is VECTOR_CST, and we call force_reg (VNx4SI, op0), which is incorrect mode
for op0. The patch fixes it by using op_mode instead of vmode in calls
to force_reg
for op0 and op1.

during RTL pass: expand
foo2.c: In function ‘foo’:
foo2.c:8:10: internal compiler error: in emit_move_insn, at expr.cc:4052
    8 |   return v2;
      |          ^~
0x74789b emit_move_insn(rtx_def*, rtx_def*)
        ../../gcc/gcc/expr.cc:4052
0xb8f664 force_reg(machine_mode, rtx_def*)
        ../../gcc/gcc/explow.cc:688
0x134182f aarch64_vectorize_vec_perm_const
        ../../gcc/gcc/config/aarch64/aarch64.cc:24132
0xe63070 expand_vec_perm_const(machine_mode, rtx_def*, rtx_def*,
int_vector_builder<poly_int<2u, long> > const&, machine_mode,
rtx_def*)
        ../../gcc/gcc/optabs.cc:6254
0xbb1569 expand_expr_real_2(separate_ops*, rtx_def*, machine_mode,
expand_modifier)
        ../../gcc/gcc/expr.cc:10273
0xbb6498 expand_expr_real_1(tree_node*, rtx_def*, machine_mode,
expand_modifier, rtx_def**, bool)
        ../../gcc/gcc/expr.cc:10625
0xa897dc expand_expr
        ../../gcc/gcc/expr.h:310
0xa897dc expand_return
        ../../gcc/gcc/cfgexpand.cc:3809
0xa897dc expand_gimple_stmt_1
        ../../gcc/gcc/cfgexpand.cc:3918
0xa897dc expand_gimple_stmt
        ../../gcc/gcc/cfgexpand.cc:4044
0xa8f238 expand_gimple_basic_block
        ../../gcc/gcc/cfgexpand.cc:6096
0xa91187 execute
        ../../gcc/gcc/cfgexpand.cc:6822

Is the patch OK to commit after bootstrap+test on aarch64-linux-gnu ?

Thanks,
Prathamesh

Prathamesh Kulkarni <prathamesh.kulkarni@linaro.org> writes:
> Hi,
> For following test case:
>
> svint32_t foo()
> {
>   int32x4_t v = (int32x4_t) { 1, 2, 3, 4 };
>   svint32_t v2 = svld1rq_s32 (svptrue_b8(), &v[0]);
>   return v2;
> }
>
> After applying workaround in forwprop to not simplify VEC_PERM_EXPR in
> simplify_permutation to avoid type error in middle end (or using
> -fno-tree-forwprop)
> as mentioned in:
> https://gcc.gnu.org/pipermail/gcc-patches/2022-July/598390.html
>
> We get following optimized gimple:
>   v2_2 = VEC_PERM_EXPR <{ 1, 2, 3, 4 }, { 1, 2, 3, 4 }, { 0, 1, 2, 3, ... }>;
>   return v2_2;

Hmm, we really should be able to fold that to a constant.  However…

> However we hit the following ICE during expansion of vec_perm_expr
> because in aarch64_vectorize_vec_perm_const,
> op0 is VECTOR_CST, and we call force_reg (VNx4SI, op0), which is incorrect mode
> for op0. The patch fixes it by using op_mode instead of vmode in calls
> to force_reg
> for op0 and op1.
>
> during RTL pass: expand
> foo2.c: In function ‘foo’:
> foo2.c:8:10: internal compiler error: in emit_move_insn, at expr.cc:4052
>     8 |   return v2;
>       |          ^~
> 0x74789b emit_move_insn(rtx_def*, rtx_def*)
>         ../../gcc/gcc/expr.cc:4052
> 0xb8f664 force_reg(machine_mode, rtx_def*)
>         ../../gcc/gcc/explow.cc:688
> 0x134182f aarch64_vectorize_vec_perm_const
>         ../../gcc/gcc/config/aarch64/aarch64.cc:24132
> 0xe63070 expand_vec_perm_const(machine_mode, rtx_def*, rtx_def*,
> int_vector_builder<poly_int<2u, long> > const&, machine_mode,
> rtx_def*)
>         ../../gcc/gcc/optabs.cc:6254
> 0xbb1569 expand_expr_real_2(separate_ops*, rtx_def*, machine_mode,
> expand_modifier)
>         ../../gcc/gcc/expr.cc:10273
> 0xbb6498 expand_expr_real_1(tree_node*, rtx_def*, machine_mode,
> expand_modifier, rtx_def**, bool)
>         ../../gcc/gcc/expr.cc:10625
> 0xa897dc expand_expr
>         ../../gcc/gcc/expr.h:310
> 0xa897dc expand_return
>         ../../gcc/gcc/cfgexpand.cc:3809
> 0xa897dc expand_gimple_stmt_1
>         ../../gcc/gcc/cfgexpand.cc:3918
> 0xa897dc expand_gimple_stmt
>         ../../gcc/gcc/cfgexpand.cc:4044
> 0xa8f238 expand_gimple_basic_block
>         ../../gcc/gcc/cfgexpand.cc:6096
> 0xa91187 execute
>         ../../gcc/gcc/cfgexpand.cc:6822
>
> Is the patch OK to commit after bootstrap+test on aarch64-linux-gnu ?
>
> Thanks,
> Prathamesh
>
> diff --git a/gcc/config/aarch64/aarch64.cc b/gcc/config/aarch64/aarch64.cc
> index 25f4cbb466d..303814b8cca 100644
> --- a/gcc/config/aarch64/aarch64.cc
> +++ b/gcc/config/aarch64/aarch64.cc
> @@ -24129,11 +24129,11 @@ aarch64_vectorize_vec_perm_const (machine_mode vmode, machine_mode op_mode,
>    d.op_mode = op_mode;
>    d.op_vec_flags = aarch64_classify_vector_mode (d.op_mode);
>    d.target = target;
> -  d.op0 = op0 ? force_reg (vmode, op0) : NULL_RTX;
> +  d.op0 = op0 ? force_reg (op_mode, op0) : NULL_RTX;
>    if (op0 == op1)
>      d.op1 = d.op0;
>    else
> -    d.op1 = op1 ? force_reg (vmode, op1) : NULL_RTX;
> +    d.op1 = op1 ? force_reg (op_mode, op1) : NULL_RTX;
>    d.testing_p = !target;
>  
>    if (!d.testing_p)

…yes, this is OK, thanks.

Richard