Hi,
> On Aug 10, 2021, at 9:16 AM, Richard Biener <rguent...@suse.de> wrote:
>
> On Tue, 10 Aug 2021, Qing Zhao wrote:
>
>>>>>
>>>>> +static void
>>>>> +expand_DEFERRED_INIT (internal_fn, gcall *stmt)
>>>>> +{
>>>>> + tree var = gimple_call_lhs (stmt);
>>>>> + tree size_of_var = gimple_call_arg (stmt, 0);
>>>>> + tree vlaaddr = NULL_TREE;
>>>>> + tree var_type = TREE_TYPE (var);
>>>>> + bool is_vla = (bool) TREE_INT_CST_LOW (gimple_call_arg (stmt, 2));
>>>>> + enum auto_init_type init_type
>>>>> + = (enum auto_init_type) TREE_INT_CST_LOW (gimple_call_arg (stmt, 1));
>>>>> +
>>>>> + gcc_assert (init_type > AUTO_INIT_UNINITIALIZED);
>>>>> +
>>>>> + /* if this variable is a VLA, get its SIZE and ADDR first. */
>>>>> + if (is_vla)
>>>>> + {
>>>>> + /* The temporary address variable for this vla should have been
>>>>> + created during gimplification phase. Refer to gimplify_vla_decl
>>>>> + for details. */
>>>>> + tree var_decl = (TREE_CODE (var) == SSA_NAME) ?
>>>>> + SSA_NAME_VAR (var) : var;
>>>>> + gcc_assert (DECL_HAS_VALUE_EXPR_P (var_decl));
>>>>> + gcc_assert (TREE_CODE (DECL_VALUE_EXPR (var_decl)) ==
>>>>> INDIRECT_REF);
>>>>> + /* Get the address of this vla variable. */
>>>>> + vlaaddr = TREE_OPERAND (DECL_VALUE_EXPR (var_decl), 0);
>>>>>
>>>>> err - isn't the address of the decl represented by the LHS
>>>>> regardless whether this is a VLA or not?
>>>>
>>>> The LHS of the call to .DEFERRED_INIT is the DECL itself whatever it’s a
>>>> VLA or not.
>>>>
>>>> In order to create a memset call, we need the Address of this DECL as the
>>>> first argument.
>>>> If the DECL is not a VLA, we just simply apply “build_fold_addr_expr” on
>>>> this DECL to get its address,
>>>> However, for VLA, during gimplification phase “gimplify_vla_decl”, we have
>>>> already created a temporary
>>>> address variable for this DECL, and recorded this address variable with
>>>> “DECL_VALUE_EXPR(DECL),
>>>> We should use this already created address variable for VLAs.
>>>
>>> So the issue is that the LHS of the .DEFERRED_INIT call is not properly
>>> gimplified. We should not have such decl there but I see we do not
>>> have IL verification that covers this.
>>
>> Don’t quite understand here: do you mean all the LHS of .DEFERRED_INIT call
>> are not properly gimplified, or
>> Only the LHS of .DEFERRED_INIT call for VLA are not properly gimplified?
>
> Especially in the VLA case but likely also in general (though unlikely
> since usually the receiver of initializations are simple enough). I'd
> expect the VLA case end up as
>
> *ptr_to_decl = .DEFERRED_INIT (...);
>
> where *ptr_to_decl is the DECL_VALUE_EXPR of the decl.
So, for the following small testing case:
====
extern void bar (int);
void foo(int n)
{
int arr[n];
bar (arr[2]);
return;
}
=====
If I compile it with -ftrivial-auto-var-init=zero -fdump-tree-gimple -S -o
auto-init-11.s -fdump-rtl-expand, the *.gimple dump is:
=====
void foo (int n)
{
int n.0;
sizetype D.1950;
bitsizetype D.1951;
sizetype D.1952;
bitsizetype D.1953;
sizetype D.1954;
int[0:D.1950] * arr.1;
void * saved_stack.2;
int arr[0:D.1950] [value-expr: *arr.1];
saved_stack.2 = __builtin_stack_save ();
try
{
n.0 = n;
_1 = (long int) n.0;
_2 = _1 + -1;
_3 = (sizetype) _2;
D.1950 = _3;
_4 = (sizetype) n.0;
_5 = (bitsizetype) _4;
_6 = _5 * 32;
D.1951 = _6;
_7 = (sizetype) n.0;
_8 = _7 * 4;
D.1952 = _8;
_9 = (sizetype) n.0;
_10 = (bitsizetype) _9;
_11 = _10 * 32;
D.1953 = _11;
_12 = (sizetype) n.0;
_13 = _12 * 4;
D.1954 = _13;
arr.1 = __builtin_alloca_with_align (D.1954, 32);
arr = .DEFERRED_INIT (D.1952, 2, 1);
_14 = (*arr.1)[2];
bar (_14);
return;
}
finally
{
__builtin_stack_restore (saved_stack.2);
}
}
====
You think that the above .DEFEERED_INIT is not correct?
It should be:
*arr.1 = .DEFERRED_INIT (D.1952. 2, 1);
?
>
>> What do you mean by “such” decl? A decl whole “DECL_VALUE_EXPR(DECL)” is
>> valid?
>
> A 'decl' that has a DECL_VALUE_EXPR should not appear in the IL, it should
> always be refered to as its DECL_VALUE_EXPR.
Okay.
Qing
>
> Richard.
>
>> Qing
>>>
