[gcc r9-9677] aarch64: Add -mtune=neoverse-512tvb

[gcc r9-9677] aarch64: Add -mtune=neoverse-512tvb

[Richard Sandiford]

https://gcc.gnu.org/g:bfcc9d9610d33cc87c25f4c598e0b57d9fc3dd96

commit r9-9677-gbfcc9d9610d33cc87c25f4c598e0b57d9fc3dd96
Author: Richard Sandiford <richard.sandiford@arm.com>
Date:   Tue Aug 17 15:15:27 2021 +0100

    aarch64: Add -mtune=neoverse-512tvb
    
    This patch adds an option to tune for Neoverse cores that have
    a total vector bandwidth of 512 bits (4x128 for Advanced SIMD
    and a vector-length-dependent equivalent for SVE).  This is intended
    to be a compromise between tuning aggressively for a single core like
    Neoverse V1 (which can be too narrow) and tuning for AArch64 cores
    in general (which can be too wide).
    
    -mcpu=neoverse-512tvb is equivalent to -mcpu=neoverse-v1
    -mtune=neoverse-512tvb.
    
    gcc/
            * doc/invoke.texi: Document -mtune=neoverse-512tvb and
            -mcpu=neoverse-512tvb.
            * config/aarch64/aarch64-cores.def (neoverse-512tvb): New entry.
            * config/aarch64/aarch64-tune.md: Regenerate.
    
    (cherry picked from commit 048039c49b96875144f67e7789fdea54abf7710b)

Diff:
---
 gcc/config/aarch64/aarch64-cores.def |  2 +-
 gcc/config/aarch64/aarch64-tune.md   |  2 +-
 gcc/doc/invoke.texi                  | 20 ++++++++++++++++++++
 3 files changed, 22 insertions(+), 2 deletions(-)

diff --git a/gcc/config/aarch64/aarch64-cores.def b/gcc/config/aarch64/aarch64-cores.def
index 3cd7db88b77..fb2faa44e06 100644
--- a/gcc/config/aarch64/aarch64-cores.def
+++ b/gcc/config/aarch64/aarch64-cores.def
@@ -115,7 +115,7 @@ AARCH64_CORE("tsv110",  tsv110, tsv110, 8_2A,  AARCH64_FL_FOR_ARCH8_2 | AARCH64_
 /* ARM ('A') cores. */
 AARCH64_CORE("zeus", zeus, cortexa57, 8_4A,  AARCH64_FL_FOR_ARCH8_4 | AARCH64_FL_SVE | AARCH64_FL_RNG | AARCH64_FL_RCPC | AARCH64_FL_F16 | AARCH64_FL_PROFILE | AARCH64_FL_SSBS, neoversev1, 0x41, 0xd40, -1)
 AARCH64_CORE("neoverse-v1", neoversev1, cortexa57, 8_4A,  AARCH64_FL_FOR_ARCH8_4 | AARCH64_FL_SVE | AARCH64_FL_RNG | AARCH64_FL_RCPC | AARCH64_FL_F16 | AARCH64_FL_PROFILE | AARCH64_FL_SSBS, neoversev1, 0x41, 0xd40, -1)
-
+AARCH64_CORE("neoverse-512tvb", neoverse512tvb, cortexa57, 8_4A,  AARCH64_FL_FOR_ARCH8_4 | AARCH64_FL_SVE | AARCH64_FL_RNG | AARCH64_FL_RCPC | AARCH64_FL_F16 | AARCH64_FL_PROFILE | AARCH64_FL_SSBS, neoversev1, INVALID_IMP, INVALID_CORE, -1)
 
 /* Qualcomm ('Q') cores. */
 AARCH64_CORE("saphira",     saphira,    saphira,    8_4A,  AARCH64_FL_FOR_ARCH8_4 | AARCH64_FL_CRYPTO | AARCH64_FL_RCPC, saphira,   0x51, 0xC01, -1)
diff --git a/gcc/config/aarch64/aarch64-tune.md b/gcc/config/aarch64/aarch64-tune.md
index 0a73e105e08..e4ae7d9b16b 100644
--- a/gcc/config/aarch64/aarch64-tune.md
+++ b/gcc/config/aarch64/aarch64-tune.md
@@ -1,5 +1,5 @@
 ;; -*- buffer-read-only: t -*-
 ;; Generated automatically by gentune.sh from aarch64-cores.def
 (define_attr "tune"
-	"cortexa35,cortexa53,cortexa57,cortexa72,cortexa73,thunderx,thunderxt88p1,thunderxt88,octeontx,octeontxt81,octeontxt83,thunderxt81,thunderxt83,emag,xgene1,falkor,qdf24xx,exynosm1,phecda,thunderx2t99p1,vulcan,thunderx2t99,cortexa55,cortexa75,cortexa76,ares,neoversen1,neoversee1,a64fx,tsv110,zeus,neoversev1,saphira,neoversen2,cortexa57cortexa53,cortexa72cortexa53,cortexa73cortexa35,cortexa73cortexa53,cortexa75cortexa55,cortexa76cortexa55"
+	"cortexa35,cortexa53,cortexa57,cortexa72,cortexa73,thunderx,thunderxt88p1,thunderxt88,octeontx,octeontxt81,octeontxt83,thunderxt81,thunderxt83,emag,xgene1,falkor,qdf24xx,exynosm1,phecda,thunderx2t99p1,vulcan,thunderx2t99,cortexa55,cortexa75,cortexa76,ares,neoversen1,neoversee1,a64fx,tsv110,zeus,neoversev1,neoverse512tvb,saphira,neoversen2,cortexa57cortexa53,cortexa72cortexa53,cortexa73cortexa35,cortexa73cortexa53,cortexa75cortexa55,cortexa76cortexa55"
 	(const (symbol_ref "((enum attr_tune) aarch64_tune)")))
diff --git a/gcc/doc/invoke.texi b/gcc/doc/invoke.texi
index 7b5f6e03d9f..7226c9cc4af 100644
--- a/gcc/doc/invoke.texi
+++ b/gcc/doc/invoke.texi
@@ -15858,6 +15858,7 @@ performance of the code.  Permissible values for this option are:
 @samp{cortex-a57}, @samp{cortex-a72}, @samp{cortex-a73}, @samp{cortex-a75},
 @samp{cortex-a76}, @samp{ares}, @samp{exynos-m1}, @samp{emag}, @samp{falkor},
 @samp{neoverse-e1}, @samp{neoverse-n1}, @samp{neoverse-n2}, @samp{neoverse-v1},
+@samp{neoverse-512tvb},
 @samp{qdf24xx}, @samp{saphira}, @samp{phecda}, @samp{xgene1}, @samp{vulcan},
 @samp{octeontx}, @samp{octeontx81},  @samp{octeontx83},
 @samp{a64fx},
@@ -15874,6 +15875,15 @@ The values @samp{cortex-a57.cortex-a53}, @samp{cortex-a72.cortex-a53},
 @samp{cortex-a75.cortex-a55}, @samp{cortex-a76.cortex-a55} specify that GCC
 should tune for a big.LITTLE system.
 
+The value @samp{neoverse-512tvb} specifies that GCC should tune
+for Neoverse cores that (a) implement SVE and (b) have a total vector
+bandwidth of 512 bits per cycle.  In other words, the option tells GCC to
+tune for Neoverse cores that can execute 4 128-bit Advanced SIMD arithmetic
+instructions a cycle and that can execute an equivalent number of SVE
+arithmetic instructions per cycle (2 for 256-bit SVE, 4 for 128-bit SVE).
+This is more general than tuning for a specific core like Neoverse V1
+but is more specific than the default tuning described below.
+
 Additionally on native AArch64 GNU/Linux systems the value
 @samp{native} tunes performance to the host system.  This option has no effect
 if the compiler is unable to recognize the processor of the host system.
@@ -15903,6 +15913,16 @@ by @option{-mtune}).  Where this option is used in conjunction
 with @option{-march} or @option{-mtune}, those options take precedence
 over the appropriate part of this option.
 
+@option{-mcpu=neoverse-512tvb} is special in that it does not refer
+to a specific core, but instead refers to all Neoverse cores that
+(a) implement SVE and (b) have a total vector bandwidth of 512 bits
+a cycle.  Unless overridden by @option{-march},
+@option{-mcpu=neoverse-512tvb} generates code that can run on a
+Neoverse V1 core, since Neoverse V1 is the first Neoverse core with
+these properties.  Unless overridden by @option{-mtune},
+@option{-mcpu=neoverse-512tvb} tunes code in the same way as for
+@option{-mtune=neoverse-512tvb}.
+
 @item -moverride=@var{string}
 @opindex moverride
 Override tuning decisions made by the back-end in response to a