Re: [PATCH V4] rs6000: Optimize cmp on rotated 16bits constant

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

Gentle ping:
https://gcc.gnu.org/pipermail/gcc-patches/2022-July/598769.html

BR,
Jeff(Jiufu)

Jiufu Guo <guojiufu@linux.ibm.com> writes:

> Hi,
>
> When checking eq/neq with a constant which has only 16bits, it can be
> optimized to check the rotated data.  By this, the constant building
> is optimized.
>
> As the example in PR103743:
> For "in == 0x8000000000000000LL", this patch generates:
>         rotldi %r3,%r3,16
>         cmpldi %cr0,%r3,32768
> instead:
>         li %r9,-1
>         rldicr %r9,%r9,0,0
>         cmpd %cr0,%r3,%r9
>
> This is a new patch to optimize compare(eq/ne) on rotatable constant.
> This patch would be more straitforward than previous patch, like:
> https://gcc.gnu.org/pipermail/gcc-patches/2022-May/595576.html.
>
> This patch pass bootstrap and regtest on ppc64 and ppc64le.
> Is it ok for trunk?  Thanks for comments!
>
> BR,
> Jeff(Jiufu)
>
>
> 	PR target/103743
>
> gcc/ChangeLog:
>
> 	* config/rs6000/rs6000-protos.h (rotate_from_leading_zeros_const):
> 	New decl.
> 	* config/rs6000/rs6000.cc (rotate_from_leading_zeros_const): New
> 	define for checking simply rotated constant.
> 	* config/rs6000/rs6000.md (*rotate_on_cmpdi): New
> 	define_insn_and_split to optimze comparing on rotated constant.
>
> gcc/testsuite/ChangeLog:
>
> 	* gcc.target/powerpc/pr103743.c: New test.
> 	* gcc.target/powerpc/pr103743_1.c: New test.
>
> ---
>  gcc/config/rs6000/rs6000-protos.h             |  1 +
>  gcc/config/rs6000/rs6000.cc                   | 29 ++++++
>  gcc/config/rs6000/rs6000.md                   | 54 ++++++++++-
>  gcc/testsuite/gcc.target/powerpc/pr103743.c   | 52 ++++++++++
>  gcc/testsuite/gcc.target/powerpc/pr103743_1.c | 95 +++++++++++++++++++
>  5 files changed, 230 insertions(+), 1 deletion(-)
>  create mode 100644 gcc/testsuite/gcc.target/powerpc/pr103743.c
>  create mode 100644 gcc/testsuite/gcc.target/powerpc/pr103743_1.c
>
> diff --git a/gcc/config/rs6000/rs6000-protos.h b/gcc/config/rs6000/rs6000-protos.h
> index 3ea01023609..bc7f6ff64ef 100644
> --- a/gcc/config/rs6000/rs6000-protos.h
> +++ b/gcc/config/rs6000/rs6000-protos.h
> @@ -35,6 +35,7 @@ extern bool xxspltib_constant_p (rtx, machine_mode, int *, int *);
>  extern int vspltis_shifted (rtx);
>  extern HOST_WIDE_INT const_vector_elt_as_int (rtx, unsigned int);
>  extern bool macho_lo_sum_memory_operand (rtx, machine_mode);
> +extern int rotate_from_leading_zeros_const (unsigned HOST_WIDE_INT, int);
>  extern int num_insns_constant (rtx, machine_mode);
>  extern int small_data_operand (rtx, machine_mode);
>  extern bool mem_operand_gpr (rtx, machine_mode);
> diff --git a/gcc/config/rs6000/rs6000.cc b/gcc/config/rs6000/rs6000.cc
> index 3ff16b8ae04..9c0996603d0 100644
> --- a/gcc/config/rs6000/rs6000.cc
> +++ b/gcc/config/rs6000/rs6000.cc
> @@ -14861,6 +14861,35 @@ rs6000_reverse_condition (machine_mode mode, enum rtx_code code)
>      return reverse_condition (code);
>  }
>  
> +/* Check if C can be rotated from an immediate which contains leading
> +   zeros at least CLZ.
> +
> +   Return the number by which C can be rotated from the immediate.
> +   Return -1 if C can not be rotated as from.  */
> +
> +int
> +rotate_from_leading_zeros_const (unsigned HOST_WIDE_INT c, int clz)
> +{
> +  /* case. 0..0xxx: already at least clz zeros.  */
> +  int lz = clz_hwi (c);
> +  if (lz >= clz)
> +    return 0;
> +
> +  /* case a. 0..0xxx0..0: at least clz zeros.  */
> +  int tz = ctz_hwi (c);
> +  if (lz + tz >= clz)
> +    return tz;
> +
> +  /* xx0..0xx: rotate enough bits firstly, then check case a.  */
> +  const int rot_bits = HOST_BITS_PER_WIDE_INT - clz + 1;
> +  unsigned HOST_WIDE_INT rc = (c >> rot_bits) | (c << (clz - 1));
> +  tz = ctz_hwi (rc);
> +  if (clz_hwi (rc) + tz >= clz)
> +    return tz + rot_bits;
> +
> +  return -1;
> +}
> +
>  /* Generate a compare for CODE.  Return a brand-new rtx that
>     represents the result of the compare.  */
>  
> diff --git a/gcc/config/rs6000/rs6000.md b/gcc/config/rs6000/rs6000.md
> index 1367a2cb779..603781b29aa 100644
> --- a/gcc/config/rs6000/rs6000.md
> +++ b/gcc/config/rs6000/rs6000.md
> @@ -7720,6 +7720,59 @@ (define_insn "*movsi_from_df"
>    "xscvdpsp %x0,%x1"
>    [(set_attr "type" "fp")])
>  
> +
> +(define_code_iterator eqne [eq ne])
> +
> +;; "i == C" ==> "rotl(i,N) == rotl(C,N)"
> +(define_insn_and_split "*rotate_on_cmpdi"
> +  [(set (pc)
> +     (if_then_else (eqne (match_operand:DI 1 "gpc_reg_operand" "r")
> +			 (match_operand:DI 2 "const_int_operand" "n"))
> +			 (label_ref (match_operand 0 ""))
> +		   (pc)))]
> +  "TARGET_POWERPC64 && !reload_completed && can_create_pseudo_p ()
> +   && num_insns_constant (operands[2], DImode) > 1
> +   && (rotate_from_leading_zeros_const (~UINTVAL (operands[2]), 49) > 0
> +       || rotate_from_leading_zeros_const (UINTVAL (operands[2]), 48) > 0)"
> +   "#"
> +   "&& 1"
> +  [(pc)]
> +{
> +  rtx cnd = XEXP (SET_SRC (single_set (curr_insn)), 0);
> +  bool ne = GET_CODE (cnd) == NE;
> +
> +  bool sgn = false;
> +  unsigned HOST_WIDE_INT C = INTVAL (operands[2]);
> +  int rot = rotate_from_leading_zeros_const (C, 48);
> +  if (rot < 0)
> +  {
> +     sgn = true;
> +     rot = rotate_from_leading_zeros_const (~C, 49);
> +  }
> +  rtx n = GEN_INT (HOST_BITS_PER_WIDE_INT - rot);
> +
> +  /* i' = rotl (i, n) */
> +  rtx op0 = gen_reg_rtx (DImode);
> +  emit_insn (gen_rtx_SET (op0, gen_rtx_ROTATE (DImode, operands[1], n)));
> +
> +  /* C' = rotl (C, n) */
> +  rtx op1 = GEN_INT ((C << INTVAL (n)) | (C >> rot));
> +
> +  /* i' ==  C' */
> +  machine_mode comp_mode = sgn ? CCmode : CCUNSmode;
> +  rtx cc = gen_reg_rtx (comp_mode);
> +  emit_insn (gen_rtx_SET (cc, gen_rtx_COMPARE (comp_mode, op0, op1)));
> +
> +  rtx cmp = ne ? gen_rtx_NE (CCmode, cc, const0_rtx)
> +	       : gen_rtx_EQ (CCmode, cc, const0_rtx);
> +  rtx loc_ref = gen_rtx_LABEL_REF (VOIDmode, operands[0]);
> +  emit_jump_insn (gen_rtx_SET (pc_rtx,
> +			       gen_rtx_IF_THEN_ELSE (VOIDmode, cmp,
> +						     loc_ref, pc_rtx)));
> +  DONE;
> +}
> +)
> +
>  ;; Split a load of a large constant into the appropriate two-insn
>  ;; sequence.
>  
> @@ -13426,7 +13479,6 @@ (define_expand "@ctr<mode>"
>  ;; rs6000_legitimate_combined_insn prevents combine creating any of
>  ;; the ctr<mode> insns.
>  
> -(define_code_iterator eqne [eq ne])
>  (define_code_attr bd [(eq "bdz") (ne "bdnz")])
>  (define_code_attr bd_neg [(eq "bdnz") (ne "bdz")])
>  
> diff --git a/gcc/testsuite/gcc.target/powerpc/pr103743.c b/gcc/testsuite/gcc.target/powerpc/pr103743.c
> new file mode 100644
> index 00000000000..e18833685fb
> --- /dev/null
> +++ b/gcc/testsuite/gcc.target/powerpc/pr103743.c
> @@ -0,0 +1,52 @@
> +/* { dg-do compile } */
> +/* { dg-require-effective-target lp64 } */
> +/* { dg-options "-O2" } */
> +/* { dg-final { scan-assembler-times "cmpldi" 10  } } */
> +/* { dg-final { scan-assembler-times "cmpdi" 4  } } */
> +/* { dg-final { scan-assembler-times "rotldi" 14  } } */
> +
> +int foo (int a);
> +
> +int __attribute__ ((noinline)) udi_fun (unsigned long long in)
> +{
> +  if (in == (0x8642000000000000ULL))
> +    return foo (1);
> +  if (in == (0x7642000000000000ULL))
> +    return foo (12);
> +  if (in == (0x8000000000000000ULL))
> +    return foo (32);
> +  if (in == (0x8000000000000001ULL))
> +    return foo (33);
> +  if (in == (0x8642FFFFFFFFFFFFULL))
> +    return foo (46);
> +  if (in == (0x7642FFFFFFFFFFFFULL))
> +    return foo (51);
> +  if (in == (0x7567000000ULL))
> +    return foo (9);
> +  if (in == (0xFFF8567FFFFFFFFFULL))
> +    return foo (19);
> +
> +  return 0;
> +}
> +
> +int __attribute__ ((noinline)) di_fun (long long in)
> +{
> +  if (in == (0x8642000000000000LL))
> +    return foo (1);
> +  if (in == (0x7642000000000000LL))
> +    return foo (12);
> +  if (in == (0x8000000000000000LL))
> +    return foo (32);
> +  if (in == (0x8000000000000001LL))
> +    return foo (33);
> +  if (in == (0x8642FFFFFFFFFFFFLL))
> +    return foo (46);
> +  if (in == (0x7642FFFFFFFFFFFFLL))
> +    return foo (51);
> +  if (in == (0x7567000000LL))
> +    return foo (9);
> +  if (in == (0xFFF8567FFFFFFFFFLL))
> +    return foo (19);
> +
> +  return 0;
> +}
> diff --git a/gcc/testsuite/gcc.target/powerpc/pr103743_1.c b/gcc/testsuite/gcc.target/powerpc/pr103743_1.c
> new file mode 100644
> index 00000000000..2c08c56714a
> --- /dev/null
> +++ b/gcc/testsuite/gcc.target/powerpc/pr103743_1.c
> @@ -0,0 +1,95 @@
> +/* { dg-do run } */
> +/* { dg-options "-O2 -std=c99" } */
> +
> +int
> +foo (int a)
> +{
> +  return a + 6;
> +}
> +
> +int __attribute__ ((noinline)) udi_fun (unsigned long long in)
> +{
> +  if (in == (0x8642000000000000ULL))
> +    return foo (1);
> +  if (in == (0x7642000000000000ULL))
> +    return foo (12);
> +  if (in == (0x8000000000000000ULL))
> +    return foo (32);
> +  if (in == (0x8000000000000001ULL))
> +    return foo (33);
> +  if (in == (0x8642FFFFFFFFFFFFULL))
> +    return foo (46);
> +  if (in == (0x7642FFFFFFFFFFFFULL))
> +    return foo (51);
> +  if (in == (0x7567000000ULL))
> +    return foo (9);
> +  if (in == (0xFFF8567FFFFFFFFFULL))
> +    return foo (19);
> +  
> +  return 0;
> +}
> +
> +int __attribute__ ((noinline)) di_fun (long long in)
> +{
> +  if (in == (0x8642000000000000LL))
> +    return foo (1);
> +  if (in == (0x7642000000000000LL))
> +    return foo (12);
> +  if (in == (0x8000000000000000LL))
> +    return foo (32);
> +  if (in == (0x8000000000000001LL))
> +    return foo (33);
> +  if (in == (0x8642FFFFFFFFFFFFLL))
> +    return foo (46);
> +  if (in == (0x7642FFFFFFFFFFFFLL))
> +    return foo (51);
> +  return 0;
> +}
> +
> +int
> +main ()
> +{
> +  int e = 0;
> +  if (udi_fun (6) != 0)
> +    e++;
> +  if (udi_fun (0x8642000000000000ULL) != foo (1))
> +    e++;
> +  if (udi_fun (0x7642000000000000ULL) != foo (12))
> +    e++;
> +  if (udi_fun (0x8000000000000000ULL) != foo (32))
> +    e++;
> +  if (udi_fun (0x8000000000000001ULL) != foo (33))
> +    e++;
> +  if (udi_fun (0x8642FFFFFFFFFFFFULL) != foo (46))
> +    e++;
> +  if (udi_fun (0x7642FFFFFFFFFFFFULL) != foo (51))
> +    e++;
> +  if (udi_fun (0x7567000000ULL) != foo (9))
> +    e++;
> +  if (udi_fun (0xFFF8567FFFFFFFFFULL) != foo (19))
> +    e++;
> +
> +  if (di_fun (6) != 0)
> +    e++;
> +  if (di_fun (0x8642000000000000LL) != foo (1))
> +    e++;
> +  if (di_fun (0x7642000000000000LL) != foo (12))
> +    e++;
> +  if (di_fun (0x8000000000000000LL) != foo (32))
> +    e++;
> +  if (di_fun (0x8000000000000001LL) != foo (33))
> +    e++;
> +  if (di_fun (0x8642FFFFFFFFFFFFLL) != foo (46))
> +    e++;
> +  if (di_fun (0x7642FFFFFFFFFFFFLL) != foo (51))
> +    e++;
> +  if (udi_fun (0x7567000000LL) != foo (9))
> +    e++;
> +  if (udi_fun (0xFFF8567FFFFFFFFFLL) != foo (19))
> +    e++;
> +
> +  if (e)
> +    __builtin_abort ();
> +  return 0;
> +}
> +