> -----Original Message-----
> From: Richard Sandiford <richard.sandif...@arm.com>
> Sent: Friday, July 26, 2024 2:12 PM
> To: Tamar Christina <tamar.christ...@arm.com>
> Cc: gcc-patches@gcc.gnu.org; nd <n...@arm.com>; Richard Earnshaw
> <richard.earns...@arm.com>; Marcus Shawcroft
> <marcus.shawcr...@arm.com>; ktkac...@gcc.gnu.org
> Subject: Re: [PATCH 1/8]AArch64: Update Neoverse V2 cost model to release
> costs
>
> Tamar Christina <tamar.christ...@arm.com> writes:
> > Hi All,
> >
> > This updates the cost for Neoverse V2 to reflect the updated
> > Software Optimization Guide.
> >
> > It also makes Cortex-X3 use the Neoverse V2 cost model.
> >
> > Bootstrapped Regtested on aarch64-none-linux-gnu and no issues.
> >
> > Ok for master?
> >
> > Thanks,
> > Tamar
> >
> > gcc/ChangeLog:
> >
> > * config/aarch64/aarch64-cores.def (cortex-x3): Use Neoverse-V2 costs.
> > * config/aarch64/tuning_models/neoversev2.h: Update costs.
> >
> > ---
> >
> > diff --git a/gcc/config/aarch64/aarch64-cores.def
> b/gcc/config/aarch64/aarch64-cores.def
> > index
> e58bc0f27de3d60d39c02d2be2aa15570bd5db4d..34307fe0c1721dda67adab7
> 68dd22a5649687f6e 100644
> > --- a/gcc/config/aarch64/aarch64-cores.def
> > +++ b/gcc/config/aarch64/aarch64-cores.def
> > @@ -186,7 +186,7 @@ AARCH64_CORE("cortex-a720", cortexa720, cortexa57,
> V9_2A, (SVE2_BITPERM, MEMTA
> >
> > AARCH64_CORE("cortex-x2", cortexx2, cortexa57, V9A, (SVE2_BITPERM,
> MEMTAG, I8MM, BF16), neoversen2, 0x41, 0xd48, -1)
> >
> > -AARCH64_CORE("cortex-x3", cortexx3, cortexa57, V9A, (SVE2_BITPERM,
> MEMTAG, I8MM, BF16), neoversen2, 0x41, 0xd4e, -1)
> > +AARCH64_CORE("cortex-x3", cortexx3, cortexa57, V9A, (SVE2_BITPERM,
> MEMTAG, I8MM, BF16), neoversev2, 0x41, 0xd4e, -1)
> >
> > AARCH64_CORE("cortex-x4", cortexx4, cortexa57, V9_2A, (SVE2_BITPERM,
> MEMTAG, PROFILE), neoversen2, 0x41, 0xd81, -1)
> >
> > diff --git a/gcc/config/aarch64/tuning_models/neoversev2.h
> b/gcc/config/aarch64/tuning_models/neoversev2.h
> > index
> f76e4ef358f7dfb9c7d7b470ea7240eaa2120f8e..cca459e32c1384f57f8345d86b
> 42b7814ae44115 100644
> > --- a/gcc/config/aarch64/tuning_models/neoversev2.h
> > +++ b/gcc/config/aarch64/tuning_models/neoversev2.h
> > @@ -57,13 +57,13 @@ static const advsimd_vec_cost
> neoversev2_advsimd_vector_cost =
> > 2, /* ld2_st2_permute_cost */
> > 2, /* ld3_st3_permute_cost */
> > 3, /* ld4_st4_permute_cost */
> > - 3, /* permute_cost */
> > + 2, /* permute_cost */
> > 4, /* reduc_i8_cost */
> > 4, /* reduc_i16_cost */
> > 2, /* reduc_i32_cost */
> > 2, /* reduc_i64_cost */
> > 6, /* reduc_f16_cost */
> > - 3, /* reduc_f32_cost */
> > + 4, /* reduc_f32_cost */
> > 2, /* reduc_f64_cost */
> > 2, /* store_elt_extra_cost */
> > /* This value is just inherited from the Cortex-A57 table. */
> > @@ -86,28 +86,28 @@ static const sve_vec_cost neoversev2_sve_vector_cost =
> > {
> > 2, /* int_stmt_cost */
> > 2, /* fp_stmt_cost */
> > - 3, /* ld2_st2_permute_cost */
> > + 2, /* ld2_st2_permute_cost */
> > 3, /* ld3_st3_permute_cost */
> > - 4, /* ld4_st4_permute_cost */
> > - 3, /* permute_cost */
> > + 3, /* ld4_st4_permute_cost */
> > + 2, /* permute_cost */
> > /* Theoretically, a reduction involving 15 scalar ADDs could
> > - complete in ~3 cycles and would have a cost of 15. [SU]ADDV
> > - completes in 11 cycles, so give it a cost of 15 + 8. */
> > - 21, /* reduc_i8_cost */
> > - /* Likewise for 7 scalar ADDs (~2 cycles) vs. 9: 7 + 7. */
> > - 14, /* reduc_i16_cost */
> > - /* Likewise for 3 scalar ADDs (~2 cycles) vs. 8: 3 + 4. */
> > + complete in ~5 cycles and would have a cost of 15. [SU]ADDV
> > + completes in 9 cycles, so give it a cost of 15 + 4. */
> > + 19, /* reduc_i8_cost */
> > + /* Likewise for 7 scalar ADDs (~3 cycles) vs. 8: 7 + 5. */
> > + 12, /* reduc_i16_cost */
> > + /* Likewise for 3 scalar ADDs (~2 cycles) vs. 6: 3 + 4. */
> > 7, /* reduc_i32_cost */
> > - /* Likewise for 1 scalar ADD (~1 cycles) vs. 2: 1 + 1. */
> > - 2, /* reduc_i64_cost */
> > + /* Likewise for 1 scalar ADDs (~1 cycles) vs. 4: 1 + 3. */
>
> Nit: old "1 scalar ADD" (singular) was correct
>
> > + 4, /* reduc_i64_cost */
> > /* Theoretically, a reduction involving 7 scalar FADDs could
> > - complete in ~6 cycles and would have a cost of 14. FADDV
> > - completes in 8 cycles, so give it a cost of 14 + 2. */
> > - 16, /* reduc_f16_cost */
> > - /* Likewise for 3 scalar FADDs (~4 cycles) vs. 6: 6 + 2. */
> > - 8, /* reduc_f32_cost */
> > - /* Likewise for 1 scalar FADD (~2 cycles) vs. 4: 2 + 2. */
> > - 4, /* reduc_f64_cost */
> > + complete in ~6 cycles and would have a cost of 7. FADDV
> > + completes in 8 cycles, so give it a cost of 7 + 2. */
> > + 9, /* reduc_f16_cost */
> > + /* Likewise for 3 scalar FADDs (~4 cycles) vs. 6: 3 + 2. */
> > + 5, /* reduc_f32_cost */
> > + /* Likewise for 1 scalar FADD (~2 cycles) vs. 4: 1 + 2. */
> > + 3, /* reduc_f64_cost */
>
> The last three seem a bit more surprising. I'd expect each scalar
> FADD to have a cost of 2 because of:
>
> 1, /* scalar_int_stmt_cost */
> 2, /* scalar_fp_stmt_cost */
>
> so the old 14 +, 6 + and 2 + look like they should be right.
Ah, thanks for spotting that. I forgot to multiply the scalar cost by
their latencies here. The integer are correct because of their cost of 1.
I'll double check if I made the same mistake over the other patches
before committing them.
Thanks,
Tamar
>
> (LGTM otherwise)
>
> Thanks,
> Richard
>
> > 2, /* store_elt_extra_cost */
> > /* This value is just inherited from the Cortex-A57 table. */
> > 8, /* vec_to_scalar_cost */
> > @@ -127,7 +127,7 @@ static const sve_vec_cost neoversev2_sve_vector_cost =
> > /* A strided Advanced SIMD x64 load would take two parallel FP loads
> > (8 cycles) plus an insertion (2 cycles). Assume a 64-bit SVE gather
> > is 1 cycle more. The Advanced SIMD version is costed as 2 scalar
> > loads
> > - (cost 8) and a vec_construct (cost 2). Add a full vector operation
> > + (cost 8) and a vec_construct (cost 4). Add a full vector operation
> > (cost 2) to that, to avoid the difference being lost in rounding.
> >
> > There is no easy comparison between a strided Advanced SIMD x32 load
> > @@ -165,14 +165,14 @@ static const aarch64_sve_vec_issue_info
> neoversev2_sve_issue_info =
> > {
> > {
> > {
> > - 3, /* loads_per_cycle */
> > + 3, /* loads_stores_per_cycle */
> > 2, /* stores_per_cycle */
> > 4, /* general_ops_per_cycle */
> > 0, /* fp_simd_load_general_ops */
> > 1 /* fp_simd_store_general_ops */
> > },
> > 2, /* ld2_st2_general_ops */
> > - 3, /* ld3_st3_general_ops */
> > + 2, /* ld3_st3_general_ops */
> > 3 /* ld4_st4_general_ops */
> > },
> > 2, /* pred_ops_per_cycle */
> > @@ -190,7 +190,7 @@ static const aarch64_vec_issue_info
> neoversev2_vec_issue_info =
> > &neoversev2_sve_issue_info
> > };
> >
> > -/* Demeter costs for vector insn classes. */
> > +/* Neoversev2 costs for vector insn classes. */
> > static const struct cpu_vector_cost neoversev2_vector_cost =
> > {
> > 1, /* scalar_int_stmt_cost */
> > @@ -243,4 +243,4 @@ static const struct tune_params neoversev2_tunings =
> > AARCH64_LDP_STP_POLICY_ALWAYS /* stp_policy_model. */
> > };
> >
> > -#endif /* GCC_AARCH64_H_NEOVERSEV2. */
> > +#endif /* GCC_AARCH64_H_NEOVERSEV2. */
> > \ No newline at end of file
