Re: [PATCH V1] HIGH part of symbol ref is invalid for constant pool

[Jiufu Guo <guojiufu@linux.ibm.com>]

"Kewen.Lin" <linkw@linux.ibm.com> writes:

> Hi Jeff,
>
> on 2022/7/19 22:30, Jiufu Guo wrote:
>> Hi,
>> 
>> In patch https://gcc.gnu.org/pipermail/gcc-patches/2022-July/597712.html,
>> test case was not added.  After more check, a testcase is added for it.
>> 
>
> Good to see that you constructed one actual test case, nice!  :)
>
>> The high part of the symbol address is invalid for the constant pool.
>> In function rs6000_cannot_force_const_mem, we already return true for
>> "HIGH with UNSPEC" rtx.  Below are some examples also indicate the high
>> part of a symbol_ref:
>> (high:DI (const:DI (plus:DI (symbol_ref:DI ("xx") (const_int 12 [0xc])))))
>> (high:DI (symbol_ref:DI ("var_1")..)))
>> 
>> This patch updates rs6000_cannot_force_const_mem to return true for
>> rtx with HIGH code.
>> 
>> Bootstrapped and regtested on ppc64le and ppc64.
>> Is it ok for trunk?
>
> I think this patch is OK with some nits below tweaked.

Thanks so much for your time to review and helpful comments!
I will update accordingly before commit.

BR,
Jeff(Jiufu)

>
>> 
>> BR,
>> Jeff(Jiufu)
>> 
>> 
>> gcc/ChangeLog:
>> 
>> 	* config/rs6000/rs6000.cc (rs6000_cannot_force_const_mem):
>> 	Return true for HIGH code rtx.
>> 
>> gcc/testsuite/ChangeLog:
>> 
>> 	* gcc.target/powerpc/constpoolcheck.c: New test.
>> 
>> ---
>>  gcc/config/rs6000/rs6000.cc                       |  7 +++++--
>>  gcc/testsuite/gcc.target/powerpc/constpoolcheck.c | 11 +++++++++++
>>  2 files changed, 16 insertions(+), 2 deletions(-)
>>  create mode 100644 gcc/testsuite/gcc.target/powerpc/constpoolcheck.c
>> 
>> diff --git a/gcc/config/rs6000/rs6000.cc b/gcc/config/rs6000/rs6000.cc
>> index 0af2085adc0..d56832ebbfc 100644
>> --- a/gcc/config/rs6000/rs6000.cc
>> +++ b/gcc/config/rs6000/rs6000.cc
>> @@ -9704,8 +9704,11 @@ rs6000_init_stack_protect_guard (void)
>>  static bool
>>  rs6000_cannot_force_const_mem (machine_mode mode ATTRIBUTE_UNUSED, rtx x)
>>  {
>> -  if (GET_CODE (x) == HIGH
>> -      && GET_CODE (XEXP (x, 0)) == UNSPEC)
>> +  /* High part of a symbol ref/address can not be put into constant pool. e.g.
>
> Nit: two spaces after the period in "... pool.".
Thanks!
>
>> +     (high:DI (symbol_ref:DI ("var")..)) or
>
> Nit: You have one "or" at the end of the above line, I think it's better to
> keep the below line consistent by either removing the above " or" or adding
> one "or" at the end of the below line.
Thanks!
>
>> +     (high:DI (unspec:DI [(symbol_ref/u:DI ("*.LC0")..)
>
>
>> +     (high:DI (const:DI (plus:DI (symbol_ref:DI ("xx")) (const_int 12)))).  */
>> +  if (GET_CODE (x) == HIGH)
>>      return true;
>> 
>>    /* A TLS symbol in the TOC cannot contain a sum.  */
>> diff --git a/gcc/testsuite/gcc.target/powerpc/constpoolcheck.c b/gcc/testsuite/gcc.target/powerpc/constpoolcheck.c
>> new file mode 100644
>> index 00000000000..ed7a994827b
>> --- /dev/null
>> +++ b/gcc/testsuite/gcc.target/powerpc/constpoolcheck.c
>
> Maybe it's good to name it to "const-pool-check.c" or "not-force-const-mem.c".
Great sugguestion! Thanks.
>
>> @@ -0,0 +1,11 @@
>> +/* { dg-do compile { target powerpc*-*-* } } */
>
> Nit: this "dg-do" line isn't needed since all here are default.
Thanks for your comments!

>
> BR,
> Kewen
>
>> +/* { dg-options "-O1 -mdejagnu-cpu=power10" } */
>> +/* (high:DI (symbol_ref:DI ("var_48")..))) should not cause ICE. */
>> +extern short var_48;
>> +void
>> +foo (double *r)
>> +{
>> +  if (var_48)
>> +    *r = 1234.5678;
>> +}
>> +