RISC-V: Add basic support for the Ventana-VT1 core

The Ventana-VT1 core is compatible with rv64gc, Zb[abcs], Zifenci and
XVentanaCondOps.
This introduces a placeholder -mcpu=ventana-vt1, so tooling and
scripts don't need to change once full support (pipeline, tuning,
etc.) will become public later.

gcc/ChangeLog:

	* config/riscv/riscv-cores.def (RISCV_TUNE): Add ventana-vt1.
	(RISCV_CORE): Ditto.
	* config/riscv/riscv-opts.h (enum riscv_microarchitecture_type): Ditto.
	* config/riscv/riscv.cc: Add tune_info for ventana-vt1.
	* doc/invoke.texi: Document -mcpu= and -mtune with ventana-vt1.

gcc/config/riscv/riscv-cores.def

@@ -38,6 +38,7 @@ RISCV_TUNE("sifive-3-series", generic, rocket_tune_info)
 RISCV_TUNE("sifive-5-series", generic, rocket_tune_info)
 RISCV_TUNE("sifive-7-series", sifive_7, sifive_7_tune_info)
 RISCV_TUNE("thead-c906", generic, thead_c906_tune_info)
+RISCV_TUNE("ventana-vt1", generic, ventana_vt1_tune_info)
 RISCV_TUNE("size", generic, optimize_size_tune_info)
 
 #undef RISCV_TUNE
@@ -73,4 +74,6 @@ RISCV_CORE("sifive-s76",      "rv64imafdc", "sifive-7-series")
 RISCV_CORE("sifive-u54",      "rv64imafdc", "sifive-5-series")
 RISCV_CORE("sifive-u74",      "rv64imafdc", "sifive-7-series")
 
+RISCV_CORE("ventana-vt1",     "rv64imafdc_zba_zbb_zbc_zbs_zifencei",	"ventana-vt1")
+
 #undef RISCV_CORE

gcc/config/riscv/riscv-opts.h

@@ -52,7 +52,7 @@ extern enum riscv_isa_spec_class riscv_isa_spec;
 /* Keep this list in sync with define_attr "tune" in riscv.md.  */
 enum riscv_microarchitecture_type {
   generic,
-  sifive_7
+  sifive_7,
 };
 extern enum riscv_microarchitecture_type riscv_microarchitecture;
 

gcc/config/riscv/riscv.cc

@@ -360,6 +360,20 @@ static const struct riscv_tune_param optimize_size_tune_info = {
   false,					/* slow_unaligned_access */
 };
 
+/* Costs to use when optimizing for Ventana Micro VT1.  */
+static const struct riscv_tune_param ventana_vt1_tune_info = {
+  {COSTS_N_INSNS (4), COSTS_N_INSNS (5)},	/* fp_add */
+  {COSTS_N_INSNS (4), COSTS_N_INSNS (5)},	/* fp_mul */
+  {COSTS_N_INSNS (20), COSTS_N_INSNS (20)},	/* fp_div */
+  {COSTS_N_INSNS (4), COSTS_N_INSNS (4)},	/* int_mul */
+  {COSTS_N_INSNS (6), COSTS_N_INSNS (6)},	/* int_div */
+  4,						/* issue_rate */
+  4,						/* branch_cost */
+  5,						/* memory_cost */
+  8,						/* fmv_cost */
+  false,					/* slow_unaligned_access */
+};
+
 static tree riscv_handle_fndecl_attribute (tree *, tree, tree, int, bool *);
 static tree riscv_handle_type_attribute (tree *, tree, tree, int, bool *);
 

gcc/doc/invoke.texi

@@ -28770,14 +28770,15 @@ by particular CPU name.
 Permissible values for this option are: @samp{sifive-e20}, @samp{sifive-e21},
 @samp{sifive-e24}, @samp{sifive-e31}, @samp{sifive-e34}, @samp{sifive-e76},
 @samp{sifive-s21}, @samp{sifive-s51}, @samp{sifive-s54}, @samp{sifive-s76},
-@samp{sifive-u54}, and @samp{sifive-u74}.
+@samp{sifive-u54}, @samp{sifive-u74}, and @samp{ventana-vt1}.
 
 @item -mtune=@var{processor-string}
 @opindex mtune
 Optimize the output for the given processor, specified by microarchitecture or
 particular CPU name.  Permissible values for this option are: @samp{rocket},
 @samp{sifive-3-series}, @samp{sifive-5-series}, @samp{sifive-7-series},
-@samp{thead-c906}, @samp{size}, and all valid options for @option{-mcpu=}.
+@samp{thead-c906}, @samp{ventana-vt1}, @samp{size}, and all valid options for
+@option{-mcpu=}.
 
 When @option{-mtune=} is not specified, use the setting from @option{-mcpu},
 the default is @samp{rocket} if both are not specified.