Re: [PATCH] rs6000: using li/lis+oris/xoris to build constants

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

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

> Hi Jeff,
>
> Sorry for late review, some comments are inline.
>
> on 2022/8/24 16:13, Jiufu Guo via Gcc-patches wrote:
>> Hi,
>> 
>> PR106708 constaint some constants which can be support by li/lis + oris/xoris.
>> 
>> For constant C:
>> if ((c & 0xFFFFFFFF80008000ULL) == 0x80000000ULL) or say:
>> 32(0)+1(1)+15(x)+1(0)+15(x), we could use li+oris to build constant 'C'.
>> 
>> if ((c & 0xFFFFFFFF00008000ULL) == 0xFFFFFFFF00008000ULL) or say:
>> 32(1)+16(x)+1(1)+15(x), using li+xoris would be ok.
>> 
>> if ((c & 0xFFFFFFFF0000FFFFULL) == 0xFFFFFFFF00000000) or say:
>> 32(1)+1(0)+15(x)+16(0), using lis+xoris would be ok.
>> 
>
> Maybe it's good to add some explanation on the proposed writing "N(M)"
> N continuous bit M, (x for M means either 1 or 0), and not sure if it's
> good to use "||" for concatenation just like what ISA uses, the con
> is it can be mis-interpreted as logical "or".
>
> Or maybe just expand all the low 32 bits and use "1..." or "0..." for the
> high 32 bits.
>
Great, thanks for sugguestions!
>> This patch update rs6000_emit_set_long_const to support these forms.
>> Bootstrap and regtest pass on ppc64 and ppc64le.
>> 
>> Is this ok for trunk?
>> 
>> BR,
>> Jeff(Jiufu)
>> 
>> 
>> 	PR target/106708
>> 
>> gcc/ChangeLog:
>> 
>> 	* config/rs6000/rs6000.cc (rs6000_emit_set_long_const): Using li/lis +
>> 	oris/xoris to build constants.
>
> Nit: Support constants which can be built with li + oris or li/lis +
> xoris?
Thanks.
>
>> 
>> gcc/testsuite/ChangeLog:
>> 
>> 	* gcc.target/powerpc/pr106708.c: New test.
>> 	* gcc.target/powerpc/pr106708.h: New file.
>> 	* gcc.target/powerpc/pr106708_1.c: New test.
>> 
>> ---
>>  gcc/config/rs6000/rs6000.cc                   | 22 +++++++++++++++++++
>>  gcc/testsuite/gcc.target/powerpc/pr106708.c   | 10 +++++++++
>>  gcc/testsuite/gcc.target/powerpc/pr106708.h   |  9 ++++++++
>>  gcc/testsuite/gcc.target/powerpc/pr106708_1.c | 17 ++++++++++++++
>>  4 files changed, 58 insertions(+)
>>  create mode 100644 gcc/testsuite/gcc.target/powerpc/pr106708.c
>>  create mode 100644 gcc/testsuite/gcc.target/powerpc/pr106708.h
>>  create mode 100644 gcc/testsuite/gcc.target/powerpc/pr106708_1.c
>> 
>> diff --git a/gcc/config/rs6000/rs6000.cc b/gcc/config/rs6000/rs6000.cc
>> index df491bee2ea..243247fb838 100644
>> --- a/gcc/config/rs6000/rs6000.cc
>> +++ b/gcc/config/rs6000/rs6000.cc
>> @@ -10112,6 +10112,7 @@ rs6000_emit_set_long_const (rtx dest, HOST_WIDE_INT c)
>>  {
>>    rtx temp;
>>    HOST_WIDE_INT ud1, ud2, ud3, ud4;
>> +  HOST_WIDE_INT orig_c = c;
>>  
>>    ud1 = c & 0xffff;
>>    c = c >> 16;
>> @@ -10137,6 +10138,27 @@ rs6000_emit_set_long_const (rtx dest, HOST_WIDE_INT c)
>>  			gen_rtx_IOR (DImode, copy_rtx (temp),
>>  				     GEN_INT (ud1)));
>>      }
>> +  else if (ud4 == 0 && ud3 == 0 && (ud2 & 0x8000) && !(ud1 & 0x8000))
>> +    {
>> +      temp = !can_create_pseudo_p () ? dest : gen_reg_rtx (DImode);
>> +
>> +      /* li+oris */
>> +      emit_move_insn (copy_rtx (temp), GEN_INT (ud1));
>
> Nit: in previous discussion on some other patch, copy_rtx is not
> necessary?
Yeap, thanks!
>
>> +      emit_move_insn (dest, gen_rtx_IOR (DImode, copy_rtx (temp),
>> +					 GEN_INT (ud2 << 16)));
>> +    }
>
> I think this hunk above can be moved to the existing "(ud3 == 0 && ud4 == 0)"
> handling branch (as the diff context below), and ud2 & 0x8000 is already
> asserted there, it also saves check.
Great, thanks for point out this. You are right, this would save some
checking.
>
>> +  else if ((ud4 == 0xffff && ud3 == 0xffff)
>> +	   && ((ud1 & 0x8000) || (ud1 == 0 && !(ud2 & 0x8000))))
>> +    {
>> +      temp = !can_create_pseudo_p () ? dest : gen_reg_rtx (DImode);
>> +
>> +      HOST_WIDE_INT imm = (ud1 & 0x8000) ? ((ud1 ^ 0x8000) - 0x8000)
>> +					 : ((ud2 << 16) - 0x80000000);
>> +      /* li/lis + xoris */
>> +      emit_move_insn (copy_rtx (temp), GEN_INT (imm));
>> +      emit_move_insn (dest, gen_rtx_XOR (DImode, copy_rtx (temp),
>> +					 GEN_INT (orig_c ^ imm)));
>> +    }
>
> Same comment for copy_rtx.
>
>>    else if (ud3 == 0 && ud4 == 0)
>>      {
>>        temp = !can_create_pseudo_p () ? dest : gen_reg_rtx (DImode);
>> diff --git a/gcc/testsuite/gcc.target/powerpc/pr106708.c b/gcc/testsuite/gcc.target/powerpc/pr106708.c
>> new file mode 100644
>> index 00000000000..6445fa47747
>> --- /dev/null
>> +++ b/gcc/testsuite/gcc.target/powerpc/pr106708.c
>> @@ -0,0 +1,10 @@
>> +/* PR target/106708 */
>> +/* { dg-options "-O2 -mdejagnu-cpu=power8" } */
>> +/* { dg-do compile { target has_arch_ppc64 } } */
>> +
>
> Put dg-do as the first line, if you want has_arch_ppc64 to be behind dg-options,
> separate it into a dg-require-effective-target.
OK, thanks!

>
>> +#include "pr106708.h"
>> +
>> +/* { dg-final { scan-assembler-times {\mli\M} 2 } } */
>> +/* { dg-final { scan-assembler-times {\mlis\M} 1 } } */
>> +/* { dg-final { scan-assembler-times {\moris\M} 1 } } */
>> +/* { dg-final { scan-assembler-times {\mxoris\M} 2 } } */
>> diff --git a/gcc/testsuite/gcc.target/powerpc/pr106708.h b/gcc/testsuite/gcc.target/powerpc/pr106708.h
>> new file mode 100644
>> index 00000000000..ad07eb30547
>> --- /dev/null
>> +++ b/gcc/testsuite/gcc.target/powerpc/pr106708.h
>> @@ -0,0 +1,9 @@
>> +/* li/lis + oris/xoris */
>
>
> Nit: /* Test constants which can be built from li + oris and li/lis + xoris.  */
>
OK, thanks.
>> +void  __attribute__ ((__noinline__, __noclone__)) foo (long long *arg)
>> +{
>> +  *arg++ = 0x98765432ULL;
>> +  *arg++ = 0xffffffff7cdeab55ULL;
>> +  *arg++ = 0xffffffff65430000ULL;
>> +}
>> +
>> +
>> diff --git a/gcc/testsuite/gcc.target/powerpc/pr106708_1.c b/gcc/testsuite/gcc.target/powerpc/pr106708_1.c
>> new file mode 100644
>> index 00000000000..df65c321f6b
>> --- /dev/null
>> +++ b/gcc/testsuite/gcc.target/powerpc/pr106708_1.c
>
> Nit: better with name pr106708-run.c?
Ok, thanks!

>
> BR,
> Kewen
>
>> @@ -0,0 +1,17 @@
>> +/* PR target/106708 */
>> +/* { dg-do run } */
>> +/* { dg-options "-O2" } */
>> +
>> +#include "pr106708.h"
>> +
>> +long long arr[] = {0x98765432ULL, 0xffffffff7cdeab55ULL, 0xffffffff65430000ULL};
>> +int
>> +main ()
>> +{
>> +  long long a[3];
>> +
>> +  foo (a);
>> +  if (__builtin_memcmp (a, arr, sizeof (arr)) != 0)
>> +    __builtin_abort ();
>> +  return 0;
>> +}