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.
	* config/aarch64/aarch64.c (neoverse512tvb_sve_vector_cost)
	(neoverse512tvb_sve_issue_info, neoverse512tvb_vec_issue_info)
	(neoverse512tvb_vector_cost, neoverse512tvb_tunings): New structures.
	(aarch64_adjust_body_cost_sve): Handle -mtune=neoverse-512tvb.
	(aarch64_adjust_body_cost): Likewise.

1 files changed, 23 insertions, 4 deletions

diff --git a/gcc/doc/invoke.texi b/gcc/doc/invoke.texi
index 32697e6..65bb998 100644
--- a/gcc/doc/invoke.texi
+++ b/gcc/doc/invoke.texi
@@ -18407,10 +18407,10 @@ performance of the code.  Permissible values for this option are:
 @samp{cortex-a65}, @samp{cortex-a65ae}, @samp{cortex-a34},
 @samp{cortex-a78}, @samp{cortex-a78ae}, @samp{cortex-a78c},
 @samp{ares}, @samp{exynos-m1}, @samp{emag}, @samp{falkor},
-@samp{neoverse-e1}, @samp{neoverse-n1}, @samp{neoverse-n2},
-@samp{neoverse-v1}, @samp{qdf24xx}, @samp{saphira},
-@samp{phecda}, @samp{xgene1}, @samp{vulcan}, @samp{octeontx},
-@samp{octeontx81},  @samp{octeontx83},
+@samp{neoverse-512tvb}, @samp{neoverse-e1}, @samp{neoverse-n1},
+@samp{neoverse-n2}, @samp{neoverse-v1}, @samp{qdf24xx},
+@samp{saphira}, @samp{phecda}, @samp{xgene1}, @samp{vulcan},
+@samp{octeontx}, @samp{octeontx81},  @samp{octeontx83},
 @samp{octeontx2}, @samp{octeontx2t98}, @samp{octeontx2t96}
 @samp{octeontx2t93}, @samp{octeontx2f95}, @samp{octeontx2f95n},
 @samp{octeontx2f95mm},
@@ -18428,6 +18428,15 @@ 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.
@@ -18457,6 +18466,16 @@ 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