Re: [PATCH 3/3]rs6000: split complicate constant to constant pool

["Kewen.Lin" <linkw@linux.ibm.com>]

Hi,

on 2023/10/25 10:00, Jiufu Guo wrote:
> Hi,
> 
> Sometimes, a complicated constant is built via 3(or more)
> instructions to build. Generally speaking, it would not be
> as faster as loading it from the constant pool (as a few
> discussions in PR63281).

I may miss some previous discussions, but I'm curious why we
chose ">=3" here, as https://gcc.gnu.org/bugzilla/show_bug.cgi?id=63281#c9
which indicates that more than 3 (>3) should be considered
with this change.

> 
> For the concern that I raised in:
> https://gcc.gnu.org/pipermail/gcc-patches/2022-August/599676.html
> The micro-cases would not be the major concern. Because as
> Segher explained in:
> https://gcc.gnu.org/bugzilla/show_bug.cgi?id=63281#c18
> It would just be about the benchmark method.
> 
> As tested on spec2017, for visible performance changes, we
> can find the runtime improvement on 500.perlbench_r about
> ~1.8% (-O2) when support loading complicates constant from
> constant pool. And no visible performance recession on
> other benchmarks.

The improvement on 500.perlbench_r looks to match what PR63281
mentioned, nice!  I'm curious that which options and which kinds
of CPUs have you tested with?  Since this is a general change,
I'd expect we can test with P8/P9/P10 at O2/O3 (or Ofast) at
least.

BR,
Kewen

> 
> Boostrap & regtest pass on ppc64{,le}.
> Is this ok for trunk?
> 
> BR,
> Jeff (Jiufu Guo)
> 
> 	PR target/63281
> 
> gcc/ChangeLog:
> 
> 	* config/rs6000/rs6000.cc (rs6000_emit_set_const): Update to split
> 	complicate constant to memory.
> 
> gcc/testsuite/ChangeLog:
> 
> 	* gcc.target/powerpc/const_anchors.c: Update to test final-rtl.	
> 	* gcc.target/powerpc/parall_5insn_const.c: Update to keep original test
> 	point.
> 	* gcc.target/powerpc/pr106550.c: Likewise..
> 	* gcc.target/powerpc/pr106550_1.c: Likewise.
> 	* gcc.target/powerpc/pr87870.c: Update according to latest behavior.
> 	* gcc.target/powerpc/pr93012.c: Likewise.
> 
> ---
>  gcc/config/rs6000/rs6000.cc                     | 16 ++++++++++++++++
>  .../gcc.target/powerpc/const_anchors.c          |  5 ++---
>  .../gcc.target/powerpc/parall_5insn_const.c     | 14 ++++++++++++--
>  gcc/testsuite/gcc.target/powerpc/pr106550.c     | 17 +++++++++++++++--
>  gcc/testsuite/gcc.target/powerpc/pr106550_1.c   | 15 +++++++++++++--
>  gcc/testsuite/gcc.target/powerpc/pr87870.c      |  5 ++++-
>  gcc/testsuite/gcc.target/powerpc/pr93012.c      |  4 +++-
>  7 files changed, 65 insertions(+), 11 deletions(-)
> 
> diff --git a/gcc/config/rs6000/rs6000.cc b/gcc/config/rs6000/rs6000.cc
> index 4690384cdbe..b9562f1ea0f 100644
> --- a/gcc/config/rs6000/rs6000.cc
> +++ b/gcc/config/rs6000/rs6000.cc
> @@ -10292,6 +10292,22 @@ rs6000_emit_set_const (rtx dest, rtx source)
>  	  c = sext_hwi (c, 32);
>  	  emit_move_insn (lo, GEN_INT (c));
>  	}
> +
> +      /* If it can be stored to the constant pool and profitable.  */
> +      else if (base_reg_operand (dest, mode)
> +	       && num_insns_constant (source, mode) > 2)
> +	{
> +	  rtx sym = force_const_mem (mode, source);
> +	  if (TARGET_TOC && SYMBOL_REF_P (XEXP (sym, 0))
> +	      && use_toc_relative_ref (XEXP (sym, 0), mode))
> +	    {
> +	      rtx toc = create_TOC_reference (XEXP (sym, 0), copy_rtx (dest));
> +	      sym = gen_const_mem (mode, toc);
> +	      set_mem_alias_set (sym, get_TOC_alias_set ());
> +	    }
> +
> +	  emit_insn (gen_rtx_SET (dest, sym));
> +	}
>        else
>  	rs6000_emit_set_long_const (dest, c);
>        break;
> diff --git a/gcc/testsuite/gcc.target/powerpc/const_anchors.c b/gcc/testsuite/gcc.target/powerpc/const_anchors.c
> index 542e2674b12..188744165f2 100644
> --- a/gcc/testsuite/gcc.target/powerpc/const_anchors.c
> +++ b/gcc/testsuite/gcc.target/powerpc/const_anchors.c
> @@ -1,5 +1,5 @@
>  /* { dg-do compile { target has_arch_ppc64 } } */
> -/* { dg-options "-O2" } */
> +/* { dg-options "-O2 -fdump-rtl-final" } */
>  
>  #define C1 0x2351847027482577ULL
>  #define C2 0x2351847027482578ULL
> @@ -16,5 +16,4 @@ void __attribute__ ((noinline)) foo1 (long long *a, long long b)
>    if (b)
>      *a++ = C2;
>  }
> -
> -/* { dg-final { scan-assembler-times {\maddi\M} 2 } } */
> +/* { dg-final { scan-rtl-dump-times {\madddi3\M} 2 "final" } } */
> diff --git a/gcc/testsuite/gcc.target/powerpc/parall_5insn_const.c b/gcc/testsuite/gcc.target/powerpc/parall_5insn_const.c
> index e3a9a7264cf..df0690b90be 100644
> --- a/gcc/testsuite/gcc.target/powerpc/parall_5insn_const.c
> +++ b/gcc/testsuite/gcc.target/powerpc/parall_5insn_const.c
> @@ -9,8 +9,18 @@
>  void __attribute__ ((noinline)) foo (unsigned long long *a)
>  {
>    /* 2 lis + 2 ori + 1 rldimi for each constant.  */
> -  *a++ = 0x800aabcdc167fa16ULL;
> -  *a++ = 0x7543a876867f616ULL;
> +  {
> +    register long long d asm("r0") = 0x800aabcdc167fa16ULL;
> +    long long n;
> +    asm("mr %0, %1" : "=r"(n) : "r"(d));
> +    *a++ = n;
> +  }
> +  {
> +    register long long d asm("r0") = 0x7543a876867f616ULL;
> +    long long n;
> +    asm("mr %0, %1" : "=r"(n) : "r"(d));
> +    *a++ = n;
> +  }
>  }
>  
>  long long A[] = {0x800aabcdc167fa16ULL, 0x7543a876867f616ULL};
> diff --git a/gcc/testsuite/gcc.target/powerpc/pr106550.c b/gcc/testsuite/gcc.target/powerpc/pr106550.c
> index 74e395331ab..5eca2b2f701 100644
> --- a/gcc/testsuite/gcc.target/powerpc/pr106550.c
> +++ b/gcc/testsuite/gcc.target/powerpc/pr106550.c
> @@ -1,12 +1,25 @@
>  /* PR target/106550 */
>  /* { dg-options "-O2 -mdejagnu-cpu=power10" } */
>  /* { dg-require-effective-target power10_ok } */
> +/* { dg-require-effective-target has_arch_ppc64 } */
>  
>  void
>  foo (unsigned long long *a)
>  {
> -  *a++ = 0x020805006106003; /* pli+pli+rldimi */
> -  *a++ = 0x2351847027482577;/* pli+pli+rldimi */  
> +  {
> +    /* pli+pli+rldimi */
> +    register long long d asm("r0") = 0x020805006106003ULL;
> +    long long n;
> +    asm("mr %0, %1" : "=r"(n) : "r"(d));
> +    *a++ = n;
> +  }
> +  {
> +    /* pli+pli+rldimi */  
> +    register long long d asm("r0") = 0x2351847027482577ULL;
> +    long long n;
> +    asm("mr %0, %1" : "=r"(n) : "r"(d));
> +    *a++ = n;
> +  }
>  }
>  
>  /* { dg-final { scan-assembler-times {\mpli\M} 4 } } */
> diff --git a/gcc/testsuite/gcc.target/powerpc/pr106550_1.c b/gcc/testsuite/gcc.target/powerpc/pr106550_1.c
> index 7e709fcf9d8..11878d893a4 100644
> --- a/gcc/testsuite/gcc.target/powerpc/pr106550_1.c
> +++ b/gcc/testsuite/gcc.target/powerpc/pr106550_1.c
> @@ -12,8 +12,19 @@ foo (unsigned long long *a)
>    asm("cntlzd %0, %1" : "=r"(n) : "r"(d));
>    *a++ = n;
>  
> -  *a++ = 0x235a8470a7480000ULL; /* pli+sldi+oris */
> -  *a++ = 0x23a184700000b677ULL; /* pli+sldi+ori */
> +  {
> +    register long long d asm("r0") = 0x235a8470a7480000ULL; /* pli+sldi+oris */
> +    long long n;
> +    asm("cntlzd %0, %1" : "=r"(n) : "r"(d));
> +    *a++ = n;
> +  }
> +
> +  {
> +    register long long d asm("r0") = 0x23a184700000b677ULL; /* pli+sldi+ori */
> +    long long n;
> +    asm("cntlzd %0, %1" : "=r"(n) : "r"(d));
> +    *a++ = n;
> +  }
>  }
>  
>  /* { dg-final { scan-assembler-times {\mpli\M} 3 } } */
> diff --git a/gcc/testsuite/gcc.target/powerpc/pr87870.c b/gcc/testsuite/gcc.target/powerpc/pr87870.c
> index d2108ac3386..5fee06744ae 100644
> --- a/gcc/testsuite/gcc.target/powerpc/pr87870.c
> +++ b/gcc/testsuite/gcc.target/powerpc/pr87870.c
> @@ -25,4 +25,7 @@ test3 (void)
>    return ((__int128)0xdeadbeefcafebabe << 64) | 0xfacefeedbaaaaaad;
>  }
>  
> -/* { dg-final { scan-assembler-not {\mld\M} } } */
> +/* test3 using "ld" to load the value for r3 and r4.
> +   test0, test1 and test2 are using "li".  */
> +/* { dg-final { scan-assembler-times {\mp?ld\M} 2 } } */
> +/* { dg-final { scan-assembler-times {\mli\M} 6 } } */
> diff --git a/gcc/testsuite/gcc.target/powerpc/pr93012.c b/gcc/testsuite/gcc.target/powerpc/pr93012.c
> index 4f764d0576f..87ce0b49b23 100644
> --- a/gcc/testsuite/gcc.target/powerpc/pr93012.c
> +++ b/gcc/testsuite/gcc.target/powerpc/pr93012.c
> @@ -10,4 +10,6 @@ unsigned long long mskh1() { return 0xffff9234ffff9234ULL; }
>  unsigned long long mskl1() { return 0x2bcdffff2bcdffffULL; }
>  unsigned long long mskse() { return 0xffff1234ffff1234ULL; }
>  
> -/* { dg-final { scan-assembler-times {\mrldimi\M} 7 } } */
> +/* { dg-final { scan-assembler-times {\mrldimi\M} 7 { target { has_arch_pwr10 } } } } */
> +/* { dg-final { scan-assembler-times {\mrldimi\M} 3 { target { ! has_arch_pwr10 } } } } */
> +/* { dg-final { scan-assembler-times {\mp?ld\M} 4 { target { ! has_arch_pwr10 } } } } */