Re: [PATCH] aarch64: Fix test_dfp_17.c for big-endian [PR 107604]

[Richard Sandiford <richard.sandiford@arm.com>]

Richard Earnshaw via Gcc-patches <gcc-patches@gcc.gnu.org> writes:
> On 22/11/2022 09:01, Christophe Lyon via Gcc-patches wrote:
>> gcc.target/aarch64/aapcs64/test_dfp_17.c has been failing on
>> big-endian, because the _Decimal32 on-stack argument is not padded in
>> the same direction depending on endianness.
>> 
>> This patch fixes the testcase so that it expects the argument in the
>> right stack location, similarly to what other tests do in the same
>> directory.
>> 
>> gcc/testsuite/ChangeLog:
>> 
>> 	PR target/107604
>> 	* gcc.target/aarch64/aapcs64/test_dfp_17.c: Fix for big-endian.
>> ---
>>   gcc/testsuite/gcc.target/aarch64/aapcs64/test_dfp_17.c | 4 ++++
>>   1 file changed, 4 insertions(+)
>> 
>> diff --git a/gcc/testsuite/gcc.target/aarch64/aapcs64/test_dfp_17.c b/gcc/testsuite/gcc.target/aarch64/aapcs64/test_dfp_17.c
>> index 22dc462bf7c..3c45f715cf7 100644
>> --- a/gcc/testsuite/gcc.target/aarch64/aapcs64/test_dfp_17.c
>> +++ b/gcc/testsuite/gcc.target/aarch64/aapcs64/test_dfp_17.c
>> @@ -32,6 +32,10 @@ struct z b = { 9.0dd, 10.0dd, 11.0dd, 12.0dd };
>>     ANON(struct z, a, D1)
>>     ANON(struct z, b, STACK)
>>     ANON(int , 5, W0)
>> +#ifndef __AAPCS64_BIG_ENDIAN__
>>     ANON(_Decimal32, f1, STACK+32) /* Note: no promotion to _Decimal64.  */
>> +#else
>> +  ANON(_Decimal32, f1, STACK+36) /* Note: no promotion to _Decimal64.  */
>> +#endif
>>     LAST_ANON(_Decimal64, 0.5dd, STACK+40)
>>   #endif
>
> Why would a Decimal32 change stack placement based on the endianness? 
> Isn't it a 4-byte object?

Yes, but PARM_BOUNDARY (64) sets a minimum alignment for all stack arguments.

Richard