[PATCH][AArch64] Fix PR79041

[Yvan Roux]

On 27 June 2017 at 16:55, Yvan Roux <yvan.roux@linaro.org> wrote:
> Hi
>
> On 27 June 2017 at 16:49, Wilco Dijkstra <Wilco.Dijkstra@arm.com> wrote:
>> As described in PR79041, -mcmodel=large -mpc-relative-literal-loads
>> may be used to avoid generating ADRP/ADD or ADRP/LDR.  However both
>> trunk and GCC7 may still emit ADRP for some constant pool literals.
>> Fix this by adding a aarch64_pcrelative_literal_loads check.
>>
>> OK for trunk/GCC7 backport?
>
> I can't approve it, but the patch is ok for me, I've built and
> regtested the very same patch for aarch64-linux-gnu,
> aarch64-none-elf and aarch64_be-none-elf targets :)
>
> Yvan
>
>> ChangeLog:
>> 2017-06-27  Wilco Dijkstra  <wdijkstr@arm.com>
>>
>>         PR target/79041
>>         * config/aarch64/aarch64.c (aarch64_classify_symbol):
>>         Avoid SYMBOL_SMALL_ABSOLUTE .
>>         * testsuite/gcc.target/aarch64/pr79041-2.c: New test.
>> --
>> diff --git a/gcc/config/aarch64/aarch64.c b/gcc/config/aarch64/aarch64.c
>> index 060cd8476d2954119daac495ecb059c9be73edbe..329d244e9cf16dbdf849e5dd02b3999caf0cd5a7 100644
>> --- a/gcc/config/aarch64/aarch64.c
>> +++ b/gcc/config/aarch64/aarch64.c
>> @@ -10042,7 +10042,7 @@ aarch64_classify_symbol (rtx x, rtx offset)
>>           /* This is alright even in PIC code as the constant
>>              pool reference is always PC relative and within
>>              the same translation unit.  */
>> -         if (CONSTANT_POOL_ADDRESS_P (x))
>> +         if (CONSTANT_POOL_ADDRESS_P (x) && !aarch64_pcrelative_literal_loads)

maybe just a small note here, in my backport patch on gcc-6-branch a
kept the existing order in the condition:

-         if (nopcrelative_literal_loads
+         if (!aarch64_pcrelative_literal_loads
              && CONSTANT_POOL_ADDRESS_P (x))

Can we keep it, or maybe I should wait for your patch to be committed
on trunk, and include its backport in my patch for GCC 6.


>>             return SYMBOL_SMALL_ABSOLUTE;
>>           else
>>             return SYMBOL_FORCE_TO_MEM;
>> diff --git a/gcc/testsuite/gcc.target/aarch64/pr79041-2.c b/gcc/testsuite/gcc.target/aarch64/pr79041-2.c
>> new file mode 100644
>> index 0000000000000000000000000000000000000000..e7899725bad2b770f8488a07f99792113275bdf2
>> --- /dev/null
>> +++ b/gcc/testsuite/gcc.target/aarch64/pr79041-2.c
>> @@ -0,0 +1,10 @@
>> +/* { dg-do compile } */
>> +/* { dg-options "-O2 -mcmodel=large -mpc-relative-literal-loads" } */
>> +
>> +__int128
>> +t (void)
>> +{
>> +  return (__int128)1 << 80;
>> +}
>> +
>> +/* { dg-final { scan-assembler "adr" } } */