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 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 - 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
>
