[PATCH] PR gcc/68256 Defining TARGET_USE_CONSTANT_BLOCKS_P causes go bootstrap failure on aarch64.

[Richard Biener]

On Mon, Feb 26, 2018 at 12:07 PM, Richard Biener
<richard.guenther@gmail.com> wrote:
> On Fri, Feb 16, 2018 at 6:18 PM,  <vladimir.mezentsev@oracle.com> wrote:
>> From: Vladimir Mezentsev <vladimir.mezentsev@oracle.com>
>>
>> Ramana Radhakrishnan made a workaround in gcc/config/aarch64/aarch64.c to resolve
>> bootstrap comparison failure (2015-11-10, commit bc443a71dafa2e707bae4b2fa74f83b05dea37ab).
>> The real bug is in gcc/varasm.c.
>> hash_section() returns an unstable value.
>> As result, two blocks are created in get_block_for_section() for one unnamed section.
>> A list of objects in these blocks depends on the -gtoggle option.
>> I removed Ramana's workaround in gcc/config/aarch64/aarch64.c and
>> I fixed hash_section() in gcc/varasm.c
>>
>> Bootstrapped on aarch64-unknown-linux-gnu including (c,c++ and go).
>> Testing finished ok.
>
> Ok.

Committed on behalf of Vladimir.  r258553.

Richard.

> Thanks,
> Richard.
>
>> ChangeLog:
>> 2018-02-15  Vladimir Mezentsev  <vladimir.mezentsev@oracle.com>
>>
>> PR gcc/68256
>> * varasm.c (hash_section): Return an unchangeble hash value
>> * config/aarch64/aarch64.c (aarch64_use_blocks_for_constant_p):
>> Return !aarch64_can_use_per_function_literal_pools_p ();
>> ---
>>  gcc/config/aarch64/aarch64.c | 8 +++-----
>>  gcc/varasm.c                 | 2 +-
>>  2 files changed, 4 insertions(+), 6 deletions(-)
>>
>> diff --git a/gcc/config/aarch64/aarch64.c b/gcc/config/aarch64/aarch64.c
>> index 174310c..a0a495d 100644
>> --- a/gcc/config/aarch64/aarch64.c
>> +++ b/gcc/config/aarch64/aarch64.c
>> @@ -7596,11 +7596,9 @@ aarch64_can_use_per_function_literal_pools_p (void)
>>  static bool
>>  aarch64_use_blocks_for_constant_p (machine_mode, const_rtx)
>>  {
>> -  /* Fixme:: In an ideal world this would work similar
>> -     to the logic in aarch64_select_rtx_section but this
>> -     breaks bootstrap in gcc go.  For now we workaround
>> -     this by returning false here.  */
>> -  return false;
>> +  /* We can't use blocks for constants when we're using a per-function
>> +     constant pool.  */
>> +  return !aarch64_can_use_per_function_literal_pools_p ();
>>  }
>>
>>  /* Select appropriate section for constants depending
>> diff --git a/gcc/varasm.c b/gcc/varasm.c
>> index b045efa..5aae5b4 100644
>> --- a/gcc/varasm.c
>> +++ b/gcc/varasm.c
>> @@ -225,7 +225,7 @@ hash_section (section *sect)
>>  {
>>    if (sect->common.flags & SECTION_NAMED)
>>      return htab_hash_string (sect->named.name);
>> -  return sect->common.flags;
>> +  return sect->common.flags & ~SECTION_DECLARED;
>>  }
>>
>>  /* Helper routines for maintaining object_block_htab.  */
>> --
>> 1.8.3.1
>>