[Bug target/103271] ICE in assign_stack_temp_for_type with -ftrivial-auto-var-init=pattern and VLAs and -mno-strict-align on riscv64

["qinzhao at gcc dot gnu.org" <gcc-bugzilla@gcc.gnu.org>]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=103271

--- Comment #17 from qinzhao at gcc dot gnu.org ---
(In reply to Richard Biener from comment #12)
> diff --git a/gcc/internal-fn.c b/gcc/internal-fn.c
> index 6ac3460d538..08f94b7a17a 100644
> --- a/gcc/internal-fn.c
> +++ b/gcc/internal-fn.c
> @@ -3050,6 +3050,23 @@ expand_DEFERRED_INIT (internal_fn, gcall *stmt)
>         lhs_base = TREE_OPERAND (lhs_base, 0);
>        reg_lhs = (mem_ref_refers_to_non_mem_p (lhs_base)
>                  || non_mem_decl_p (lhs_base));
> +      /* If this expands to a register and the underlying decl is wrapped in
> +        a MEM_REF that just serves as an access type change expose the decl
> +        if it is of correct size.  This avoids a situation as in PR103271
> +        if the target does not support a direct move to the registers mode.
> */
> +      if (reg_lhs
> +         && TREE_CODE (lhs_base) == MEM_REF
> +         && TREE_CODE (TREE_OPERAND (lhs_base, 0)) == ADDR_EXPR
> +         && DECL_P (TREE_OPERAND (TREE_OPERAND (lhs_base, 0), 0))
> +         && integer_zerop (TREE_OPERAND (lhs_base, 1))
> +         && tree_fits_uhwi_p (var_size)
> +         && tree_int_cst_equal
> +              (var_size,
> +               DECL_SIZE_UNIT (TREE_OPERAND (TREE_OPERAND (lhs_base, 0),
> 0))))
> +       {
> +         lhs = TREE_OPERAND (TREE_OPERAND (lhs_base, 0), 0);
> +         var_type = TREE_TYPE (lhs);
> +       }
>      }
>  
>    if (!reg_lhs)
> 
> solves the issue.  There might be a situation where that's not enough though,
> I'm giving the above some testing.
this patch is so specific to target this specific case, I am wondering whether
this is needed if Tim will provide a patch to support MOVTI in riscv backend?