[PING][PATCH v3] Disable reg offset in quad-word store for Falkor

[Siddhesh Poyarekar <siddhesh@sourceware.org>]

Ping!

On Friday 09 February 2018 01:02 PM, Siddhesh Poyarekar wrote:
> Hi,
> 
> Here's v3 of the patch to disable register offset addressing mode for
> stores of 128-bit values on Falkor because they're very costly.
> Following Kyrill's suggestion, I compared the codegen for a53 and
> found that the codegen was quite different.  Jim's original patch is
> the most minimal compromise for this and is also a cleaner temporary
> fix before I attempt to split address costs into loads and stores for
> gcc9.
> 
> So v3 is essentially a very slightly cleaned up version of v1 again,
> this time with confirmation that there are no codegen changes in
> CPU2017 on non-falkor builds; only the codegen for -mcpu=falkor is
> different.
> 
> ----
> 
> On Falkor, because of an idiosyncracy of how the pipelines are
> designed, a quad-word store using a reg+reg addressing mode is almost
> twice as slow as an add followed by a quad-word store with a single
> reg addressing mode.  So we get better performance if we disallow
> addressing modes using register offsets with quad-word stores.  This
> is the most minimal change for gcc8, I will volunteer to make a more
> lasting change for gcc9 where I split the addressing mode costs into
> loads and stores wherever possible and needed.
> 
> This patch improves fpspeed by 0.17% and intspeed by 0.62% in CPU2017,
> with xalancbmk_s (3.84%) wrf_s (1.46%) and mcf_s (1.62%) being the
> biggest winners.  There were no regressions beyond 0.4%.
> 
> 2018-xx-xx  Jim Wilson  <jim.wilson@linaro.org>
>             Kugan Vivenakandarajah  <kugan.vivekanandarajah@linaro.org>
> 	    Siddhesh Poyarekar  <siddhesh@sourceware.org>
> 
> 	gcc/
> 	* config/aarch64/aarch64-protos.h (aarch64_movti_target_operand_p):
> 	New.
> 	* config/aarch64/aarch64-simd.md (aarch64_simd_mov<mode>): Use Utf.
> 	* config/aarch64/aarch64-tuning-flags.def
> 	(SLOW_REGOFFSET_QUADWORD_STORE): New.
> 	* config/aarch64/aarch64.c (qdf24xx_tunings): Add
> 	SLOW_REGOFFSET_QUADWORD_STORE to tuning flags.
> 	(aarch64_movti_target_operand_p): New.
> 	* config/aarch64/aarch64.md (movti_aarch64): Use Utf.
> 	(movtf_aarch64): Likewise.
> 	* config/aarch64/constraints.md (Utf): New.
> 
> 	gcc/testsuite
> 	* gcc.target/aarch64/pr82533.c: New test case.
> ---
>  gcc/config/aarch64/aarch64-protos.h         |  1 +
>  gcc/config/aarch64/aarch64-simd.md          |  4 ++--
>  gcc/config/aarch64/aarch64-tuning-flags.def |  4 ++++
>  gcc/config/aarch64/aarch64.c                | 14 +++++++++++++-
>  gcc/config/aarch64/aarch64.md               |  8 ++++----
>  gcc/config/aarch64/constraints.md           |  6 ++++++
>  gcc/testsuite/gcc.target/aarch64/pr82533.c  | 11 +++++++++++
>  7 files changed, 41 insertions(+), 7 deletions(-)
>  create mode 100644 gcc/testsuite/gcc.target/aarch64/pr82533.c
> 
> diff --git a/gcc/config/aarch64/aarch64-protos.h b/gcc/config/aarch64/aarch64-protos.h
> index cda2895d28e..5a0323deb1e 100644
> --- a/gcc/config/aarch64/aarch64-protos.h
> +++ b/gcc/config/aarch64/aarch64-protos.h
> @@ -433,6 +433,7 @@ bool aarch64_simd_mem_operand_p (rtx);
>  bool aarch64_sve_ld1r_operand_p (rtx);
>  bool aarch64_sve_ldr_operand_p (rtx);
>  bool aarch64_sve_struct_memory_operand_p (rtx);
> +bool aarch64_movti_target_operand_p (rtx);
>  rtx aarch64_simd_vect_par_cnst_half (machine_mode, int, bool);
>  rtx aarch64_tls_get_addr (void);
>  tree aarch64_fold_builtin (tree, int, tree *, bool);
> diff --git a/gcc/config/aarch64/aarch64-simd.md b/gcc/config/aarch64/aarch64-simd.md
> index 3d1f6a01cb7..f7daac3e28d 100644
> --- a/gcc/config/aarch64/aarch64-simd.md
> +++ b/gcc/config/aarch64/aarch64-simd.md
> @@ -131,9 +131,9 @@
>  
>  (define_insn "*aarch64_simd_mov<VQ:mode>"
>    [(set (match_operand:VQ 0 "nonimmediate_operand"
> -		"=w, Umq,  m,  w, ?r, ?w, ?r, w")
> +		"=w, Umq, Utf,  w, ?r, ?w, ?r, w")
>  	(match_operand:VQ 1 "general_operand"
> -		"m,  Dz, w,  w,  w,  r,  r, Dn"))]
> +		"m,  Dz,    w,  w,  w,  r,  r, Dn"))]
>    "TARGET_SIMD
>     && (register_operand (operands[0], <MODE>mode)
>         || aarch64_simd_reg_or_zero (operands[1], <MODE>mode))"
> diff --git a/gcc/config/aarch64/aarch64-tuning-flags.def b/gcc/config/aarch64/aarch64-tuning-flags.def
> index ea9ead234cb..04baf5b6de6 100644
> --- a/gcc/config/aarch64/aarch64-tuning-flags.def
> +++ b/gcc/config/aarch64/aarch64-tuning-flags.def
> @@ -41,4 +41,8 @@ AARCH64_EXTRA_TUNING_OPTION ("slow_unaligned_ldpw", SLOW_UNALIGNED_LDPW)
>     are not considered cheap.  */
>  AARCH64_EXTRA_TUNING_OPTION ("cheap_shift_extend", CHEAP_SHIFT_EXTEND)
>  
> +/* Don't use a register offset in a memory address for a quad-word store.  */
> +AARCH64_EXTRA_TUNING_OPTION ("slow_regoffset_quadword_store",
> +			     SLOW_REGOFFSET_QUADWORD_STORE)
> +
>  #undef AARCH64_EXTRA_TUNING_OPTION
> diff --git a/gcc/config/aarch64/aarch64.c b/gcc/config/aarch64/aarch64.c
> index 228fd1b908d..c0a05598415 100644
> --- a/gcc/config/aarch64/aarch64.c
> +++ b/gcc/config/aarch64/aarch64.c
> @@ -875,7 +875,7 @@ static const struct tune_params qdf24xx_tunings =
>    2,	/* min_div_recip_mul_df.  */
>    0,	/* max_case_values.  */
>    tune_params::AUTOPREFETCHER_WEAK,	/* autoprefetcher_model.  */
> -  (AARCH64_EXTRA_TUNE_NONE),		/* tune_flags.  */
> +  (AARCH64_EXTRA_TUNE_SLOW_REGOFFSET_QUADWORD_STORE),	/* tune_flags.  */
>    &qdf24xx_prefetch_tune
>  };
>  
> @@ -13634,6 +13634,18 @@ aarch64_sve_struct_memory_operand_p (rtx op)
>  	  && offset_4bit_signed_scaled_p (SVE_BYTE_MODE, last));
>  }
>  
> +/* Return TRUE if OP uses an efficient memory address for quad-word target.  */
> +bool
> +aarch64_movti_target_operand_p (rtx op)
> +{
> +  if (! optimize_size
> +      && (aarch64_tune_params.extra_tuning_flags
> +	  & AARCH64_EXTRA_TUNE_SLOW_REGOFFSET_QUADWORD_STORE))
> +    return MEM_P (op) && ! (GET_CODE (XEXP (op, 0)) == PLUS
> +			    && ! CONST_INT_P (XEXP (XEXP (op, 0), 1)));
> +  return MEM_P (op);
> +}
> +
>  /* Emit a register copy from operand to operand, taking care not to
>     early-clobber source registers in the process.
>  
> diff --git a/gcc/config/aarch64/aarch64.md b/gcc/config/aarch64/aarch64.md
> index 5a2a9309a3b..1e6edcf51f2 100644
> --- a/gcc/config/aarch64/aarch64.md
> +++ b/gcc/config/aarch64/aarch64.md
> @@ -1080,9 +1080,9 @@
>  
>  (define_insn "*movti_aarch64"
>    [(set (match_operand:TI 0
> -	 "nonimmediate_operand"  "=   r,w, r,w,r,m,m,w,m")
> +	 "nonimmediate_operand"  "=   r,w, r,w,r,m,m,w,Utf")
>  	(match_operand:TI 1
> -	 "aarch64_movti_operand" " rUti,r, w,w,m,r,Z,m,w"))]
> +	 "aarch64_movti_operand" " rUti,r, w,w,m,r,Z,m,  w"))]
>    "(register_operand (operands[0], TImode)
>      || aarch64_reg_or_zero (operands[1], TImode))"
>    "@
> @@ -1227,9 +1227,9 @@
>  
>  (define_insn "*movtf_aarch64"
>    [(set (match_operand:TF 0
> -	 "nonimmediate_operand" "=w,?&r,w ,?r,w,?w,w,m,?r,m ,m")
> +	 "nonimmediate_operand" "=w,?&r,w ,?r,w,?w,w,Utf,?r,m ,m")
>  	(match_operand:TF 1
> -	 "general_operand"      " w,?r, ?r,w ,Y,Y ,m,w,m ,?r,Y"))]
> +	 "general_operand"      " w,?r, ?r,w ,Y,Y ,m,w  ,m ,?r,Y"))]
>    "TARGET_FLOAT && (register_operand (operands[0], TFmode)
>      || aarch64_reg_or_fp_zero (operands[1], TFmode))"
>    "@
> diff --git a/gcc/config/aarch64/constraints.md b/gcc/config/aarch64/constraints.md
> index f052103e859..35aa62996ae 100644
> --- a/gcc/config/aarch64/constraints.md
> +++ b/gcc/config/aarch64/constraints.md
> @@ -235,6 +235,12 @@
>    (and (match_code "mem")
>         (match_test "aarch64_sve_ldr_operand_p (op)")))
>  
> +(define_memory_constraint "Utf"
> +  "@internal
> +   An efficient memory address for a quad-word target operand."
> +  (and (match_code "mem")
> +       (match_test "aarch64_movti_target_operand_p (op)")))
> +
>  (define_memory_constraint "Utv"
>    "@internal
>     An address valid for loading/storing opaque structure
> diff --git a/gcc/testsuite/gcc.target/aarch64/pr82533.c b/gcc/testsuite/gcc.target/aarch64/pr82533.c
> new file mode 100644
> index 00000000000..fa28ffac03a
> --- /dev/null
> +++ b/gcc/testsuite/gcc.target/aarch64/pr82533.c
> @@ -0,0 +1,11 @@
> +/* { dg-do compile } */
> +/* { dg-options "-mcpu=falkor -O2 -ftree-vectorize" } */
> +
> +void
> +copy (int N, double *c, double *a)
> +{
> +  for (int i = 0; i < N; ++i)
> +    c[i] = a[i];
> +}
> +
> +/* { dg-final { scan-assembler-not "str\tq\[0-9\]+, \\\[x\[0-9\]+, x\[0-9\]+\\\]" } } */
>