llvm dev - Oct 2019 - Static assert fails when compiler for i386

Hi Devs,
Consider below testcase.
$cat test.cpp
#include <vector>
#include<type_traits>
typedef int _int4 __attribute__((vector_size(16)));
typedef union{
int data[4];
struct {int x, y, z, w;};
_int4 vec;
} int4;
typedef int4 int3;
int main()
{
static_assert(std::alignment_of<int4>::value <= alignof(max_align_t),
"over
aligned!");
}

$clang++ -m32
error: static_assert failed due to requirement
'std::alignment_of<int4>::value <= alignof(max_align_t)'
"over aligned
it goes smooth when compile for x86_64.
Following changes fixes this.

diff --git a/clang/lib/Headers/__stddef_max_align_t.h
b/clang/lib/Headers/__stddef_max_align_t.h
index e3b439285d0..46f705a09c3 100644
--- a/clang/lib/Headers/__stddef_max_align_t.h
+++ b/clang/lib/Headers/__stddef_max_align_t.h
@@ -21,6 +21,10 @@ typedef struct {
       __attribute__((__aligned__(__alignof__(long long))));
   long double __clang_max_align_nonce2
       __attribute__((__aligned__(__alignof__(long double))));
+  #ifdef __i386__
+  typedef double xx __attribute__((vector_size(16)));
+  xx __clang_max_align_nonce3
 __attribute__((__aligned__(__alignof__(xx))));
+  #endif
 } max_align_t;
 #endif

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max_align_t is a type whose alignment requirement is as large as any
*scalar* type, but your int4 is not a scalar type but a union containing a
vector _int4, so it looks like your assertion is simply incorrect.

On Thu, Oct 17, 2019 at 12:58 PM kamlesh kumar via llvm-dev <
llvm-dev at lists.llvm.org> wrote:
> Hi Devs,
> Consider below testcase.
> $cat test.cpp
> #include <vector>
> #include<type_traits>
> typedef int _int4 __attribute__((vector_size(16)));
> typedef union{
> int data[4];
> struct {int x, y, z, w;};
> _int4 vec;
> } int4;
> typedef int4 int3;
> int main()
> {
> static_assert(std::alignment_of<int4>::value <=
alignof(max_align_t), "over
> aligned!");
> }
>
> $clang++ -m32
> error: static_assert failed due to requirement
> 'std::alignment_of<int4>::value <= alignof(max_align_t)'
"over aligned
> it goes smooth when compile for x86_64.
> Following changes fixes this.
>
> diff --git a/clang/lib/Headers/__stddef_max_align_t.h
> b/clang/lib/Headers/__stddef_max_align_t.h
> index e3b439285d0..46f705a09c3 100644
> --- a/clang/lib/Headers/__stddef_max_align_t.h
> +++ b/clang/lib/Headers/__stddef_max_align_t.h
> @@ -21,6 +21,10 @@ typedef struct {
>        __attribute__((__aligned__(__alignof__(long long))));
>    long double __clang_max_align_nonce2
>        __attribute__((__aligned__(__alignof__(long double))));
> +  #ifdef __i386__
> +  typedef double xx __attribute__((vector_size(16)));
> +  xx __clang_max_align_nonce3
>  __attribute__((__aligned__(__alignof__(xx))));
> +  #endif
>  } max_align_t;
>  #endif
>
> Like to know community thought on this?
> _______________________________________________
> LLVM Developers mailing list
> llvm-dev at lists.llvm.org
> https://lists.llvm.org/cgi-bin/mailman/listinfo/llvm-dev
>
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Thank you, Rui for clarification.

On Thu, Oct 17, 2019 at 10:25 AM Rui Ueyama <ruiu at google.com> wrote:
> max_align_t is a type whose alignment requirement is as large as any
> *scalar* type, but your int4 is not a scalar type but a union containing
> a vector _int4, so it looks like your assertion is simply incorrect.
>
> On Thu, Oct 17, 2019 at 12:58 PM kamlesh kumar via llvm-dev <
> llvm-dev at lists.llvm.org> wrote:
>
>> Hi Devs,
>> Consider below testcase.
>> $cat test.cpp
>> #include <vector>
>> #include<type_traits>
>> typedef int _int4 __attribute__((vector_size(16)));
>> typedef union{
>> int data[4];
>> struct {int x, y, z, w;};
>> _int4 vec;
>> } int4;
>> typedef int4 int3;
>> int main()
>> {
>> static_assert(std::alignment_of<int4>::value <=
alignof(max_align_t), "over
>> aligned!");
>> }
>>
>> $clang++ -m32
>> error: static_assert failed due to requirement
>> 'std::alignment_of<int4>::value <=
alignof(max_align_t)' "over aligned
>> it goes smooth when compile for x86_64.
>> Following changes fixes this.
>>
>> diff --git a/clang/lib/Headers/__stddef_max_align_t.h
>> b/clang/lib/Headers/__stddef_max_align_t.h
>> index e3b439285d0..46f705a09c3 100644
>> --- a/clang/lib/Headers/__stddef_max_align_t.h
>> +++ b/clang/lib/Headers/__stddef_max_align_t.h
>> @@ -21,6 +21,10 @@ typedef struct {
>>        __attribute__((__aligned__(__alignof__(long long))));
>>    long double __clang_max_align_nonce2
>>        __attribute__((__aligned__(__alignof__(long double))));
>> +  #ifdef __i386__
>> +  typedef double xx __attribute__((vector_size(16)));
>> +  xx __clang_max_align_nonce3
>>  __attribute__((__aligned__(__alignof__(xx))));
>> +  #endif
>>  } max_align_t;
>>  #endif
>>
>> Like to know community thought on this?
>> _______________________________________________
>> LLVM Developers mailing list
>> llvm-dev at lists.llvm.org
>> https://lists.llvm.org/cgi-bin/mailman/listinfo/llvm-dev
>>
>
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