> On Oct 4, 2021, at 12:19 PM, Richard Biener <rguent...@suse.de> wrote:
>
> On October 4, 2021 7:00:10 PM GMT+02:00, Qing Zhao <qing.z...@oracle.com>
> wrote:
>> I have several questions on this fix:
>>
>> 1. This fix avoided expanding “.DEFERRED_INIT” when !tree_fits_uhwi_p
>> (TYPE_SIZE_UNIT (var_type)).
>> As a result, this call to .DEFERRED_INIT will NOT be expanded at all.
>
> Yes.
Then, should we exclude such auto init during gimplification phase?
>
>> Then not expanding .DEFERRED_INIT in RTL expanding phase will trigger more
>> issues in later RTL phases, this looks not correct to me. (Actually, with is
>> the patch, this testing case still failed in a later RTL stage).
>>
>> So, If we really want to avoid auto-init for VLA vectors, we should not
>> add call to .DEFERRED_INIT in gimplification phase at all.
>>
>>
>> 2. For the added .DEFERRED_INIT:
>>
>> __SVFloat64_t f64;
>>
>> f64 = .DEFERRED_INIT (POLY_INT_CST [16, 16], 2, 0);
>>
>> What does “POLY_INT_CST[16,16]” mean? Is this a constant size? If YES,
>> what’s the value of it? If Not, can we use “memset” to expand it?
>
> When the target is a register memset doesn't work. I'm not sure the memset
> expansion path will work as-is either for aggregates with vla parts -
Stupid question here: what does POLY_INT_CST[16,16] mean? It’s not a
constant?
Qing
> but I'll leave that to Richard S. to sort out.
>
> Richard.
>
>> Thanks.
>>
>> Qing
>>
>>
>>
>>> On Oct 4, 2021, at 3:57 AM, Richard Biener via Gcc-patches
>>> <gcc-patches@gcc.gnu.org> wrote:
>>>
>>> This avoids ICEing for VLA vector auto-init by not initializing.
>>>
>>> Bootstrapped and tested on x86_64-unknown-linux-gnu, pushed.
>>>
>>> 2021-10-04 Richard Biener <rguent...@suse.de>
>>>
>>> PR middle-end/102587
>>> * internal-fn.c (expand_DEFERRED_INIT): Guard register
>>> initialization path an avoid initializing VLA registers
>>> with it.
>>>
>>> * gcc.target/aarch64/sve/pr102587-1.c: New testcase.
>>> * gcc.target/aarch64/sve/pr102587-2.c: Likewise.
>>> ---
>>> gcc/internal-fn.c | 3 ++-
>>> gcc/testsuite/gcc.target/aarch64/sve/pr102587-1.c | 4 ++++
>>> gcc/testsuite/gcc.target/aarch64/sve/pr102587-2.c | 4 ++++
>>> 3 files changed, 10 insertions(+), 1 deletion(-)
>>> create mode 100644 gcc/testsuite/gcc.target/aarch64/sve/pr102587-1.c
>>> create mode 100644 gcc/testsuite/gcc.target/aarch64/sve/pr102587-2.c
>>>
>>> diff --git a/gcc/internal-fn.c b/gcc/internal-fn.c
>>> index 8312d08aab2..ef5dc90db56 100644
>>> --- a/gcc/internal-fn.c
>>> +++ b/gcc/internal-fn.c
>>> @@ -3035,7 +3035,8 @@ expand_DEFERRED_INIT (internal_fn, gcall *stmt)
>>> /* Expand this memset call. */
>>> expand_builtin_memset (m_call, NULL_RTX, TYPE_MODE (var_type));
>>> }
>>> - else
>>> + /* ??? Deal with poly-int sized registers. */
>>> + else if (tree_fits_uhwi_p (TYPE_SIZE_UNIT (var_type)))
>>> {
>>> /* If this variable is in a register, use expand_assignment might
>>> generate better code. */
>>> diff --git a/gcc/testsuite/gcc.target/aarch64/sve/pr102587-1.c
>>> b/gcc/testsuite/gcc.target/aarch64/sve/pr102587-1.c
>>> new file mode 100644
>>> index 00000000000..2b9a68b0b59
>>> --- /dev/null
>>> +++ b/gcc/testsuite/gcc.target/aarch64/sve/pr102587-1.c
>>> @@ -0,0 +1,4 @@
>>> +/* { dg-do compile } */
>>> +/* { dg-options "-ftrivial-auto-var-init=zero" } */
>>> +
>>> +void foo() { __SVFloat64_t f64; }
>>> diff --git a/gcc/testsuite/gcc.target/aarch64/sve/pr102587-2.c
>>> b/gcc/testsuite/gcc.target/aarch64/sve/pr102587-2.c
>>> new file mode 100644
>>> index 00000000000..4cdb9056002
>>> --- /dev/null
>>> +++ b/gcc/testsuite/gcc.target/aarch64/sve/pr102587-2.c
>>> @@ -0,0 +1,4 @@
>>> +/* { dg-do compile } */
>>> +/* { dg-options "-ftrivial-auto-var-init=pattern" } */
>>> +
>>> +void foo() { __SVFloat64_t f64; }
>>> --
>>> 2.31.1
>>
>
