Re: [PATCH] go/100537 - Bootstrap-O3 and bootstrap-debug fail

[guojiufu via Gcc-patches]

On 2021-05-17 16:17, Richard Biener wrote:

On Fri, May 14, 2021 at 11:19 AM guojiufu via Gcc-patches
<gcc-patches@gcc.gnu.org> wrote:

On 2021-05-14 15:39, guojiufu via Gcc-patches wrote:
> On 2021-05-14 15:15, Richard Biener wrote:
>> On May 14, 2021 4:52:56 AM GMT+02:00, Jiufu Guo
>> <guoji...@linux.ibm.com> wrote:
>>> As discussed in the PR, Richard mentioned the method to
>>> figure out which VAR was not set TREE_ADDRESSABLE, and
>>> then cause this failure.  It is address_expression which
>>> build addr_expr (build_fold_addr_expr_loc), but not set
>>> TREE_ADDRESSABLE.
>>>
>>> I drafted this patch with reference the comments from Richard
>>> in this PR, while I'm not quite sure if more thing need to do.
>>> So, please have review, thanks!
>>>
>>> Bootstrap and regtest pass on ppc64le. Is this ok for trunk?
>>
>> I suggest to use mark_addresssable unless we're sure expr is always an
>> entity where TREE_ADDRESSABLE has the desired meaning.

Thanks, Richard!
You point out the root concern, I'm not sure ;)

With looking at code "mark_addresssable" and code around
tree-ssa.c:1013,
VAR_P, PARM_DECL, and RESULT_DECL are checked before accessing
TREE_ADDRESSABLE.
So, just wondering if these entities need to be marked as
TREE_ADDRESSABLE?

diff --git a/gcc/go/go-gcc.cc b/gcc/go/go-gcc.cc
index 5d9dbb5d068..85d324a92cc 100644
--- a/gcc/go/go-gcc.cc
+++ b/gcc/go/go-gcc.cc
@@ -1680,6 +1680,11 @@ Gcc_backend::address_expression(Bexpression*
bexpr, Location location)
    if (expr == error_mark_node)
      return this->error_expression();

+  if ((VAR_P(expr)
+       || TREE_CODE(expr) == PARM_DECL
+       || TREE_CODE(expr) == RESULT_DECL)
+    TREE_ADDRESSABLE (expr) = 1;
+

The root concern is that mark_addressable does

  while (handled_component_p (x))
    x = TREE_OPERAND (x, 0);

and I do not know the constraints on 'expr' as passed to
Gcc_backend::address_expression.

I think we need input from Ian here. Most FEs have their own *_mark_addressable

function where they also emit diagnostics (guess this is handled in
the actual Go frontend).

Since Gcc_backend does lowering to GENERIC using a middle-end is probably OK.

Yeap.  Hope this patch is ok, then the bootstrap could pass.
Otherwise, we may need more help from Ian and guys ;)

Jiufu Guo.

tree ret = build_fold_addr_expr_loc(location.gcc_location(), expr);

    return this->make_expression(ret);
  }


Or call mark_addressable, and update mark_addressable to avoid NULL
pointer ICE:
The below patch also pass bootstrap-debug.

diff --git a/gcc/gimple-expr.c b/gcc/gimple-expr.c
index b8c732b632a..f682841391b 100644
--- a/gcc/gimple-expr.c
+++ b/gcc/gimple-expr.c
@@ -915,6 +915,7 @@ mark_addressable (tree x)
    if (TREE_CODE (x) == VAR_DECL
        && !DECL_EXTERNAL (x)
        && !TREE_STATIC (x)
+      && cfun != NULL

I'd be OK with this hunk of course.

        && cfun->gimple_df != NULL
        && cfun->gimple_df->decls_to_pointers != NULL)
      {
diff --git a/gcc/go/go-gcc.cc b/gcc/go/go-gcc.cc
index 5d9dbb5d068..fe9dfaf8579 100644
--- a/gcc/go/go-gcc.cc
+++ b/gcc/go/go-gcc.cc
@@ -1680,6 +1680,7 @@ Gcc_backend::address_expression(Bexpression*
bexpr, Location location)
    if (expr == error_mark_node)
      return this->error_expression();

+  mark_addressable(expr);

tree ret = build_fold_addr_expr_loc(location.gcc_location(), expr);

    return this->make_expression(ret);
  }


>
> I notice you mentioned "mark_addresssable" in PR.
> And I had tried yesterday, it cause new ICEs at gimple-expr.c:918
> below line:
>
>   && cfun->gimple_df != NULL
>
>
>
>>
>> Richard.
>>
>>> Jiufu Guo.
>>>
>>> 2021-05-14  Richard Biener  <rguent...@suse.de>
>>>         Jiufu Guo <guoji...@linux.ibm.com>
>>>
>>>         PR go/100537
>>>         * go-gcc.cc
>>>         (Gcc_backend::address_expression): Set TREE_ADDRESSABLE.
>>>
>>> ---
>>> gcc/go/go-gcc.cc | 1 +
>>> 1 file changed, 1 insertion(+)
>>>
>>> diff --git a/gcc/go/go-gcc.cc b/gcc/go/go-gcc.cc
>>> index 5d9dbb5d068..8ed20a3b479 100644
>>> --- a/gcc/go/go-gcc.cc
>>> +++ b/gcc/go/go-gcc.cc
>>> @@ -1680,6 +1680,7 @@ Gcc_backend::address_expression(Bexpression*
>>> bexpr, Location location)
>>>   if (expr == error_mark_node)
>>>     return this->error_expression();
>>>
>>> +  TREE_ADDRESSABLE (expr) = 1;
>>>   tree ret = build_fold_addr_expr_loc(location.gcc_location(), expr);
>>>   return this->make_expression(ret);
>>> }