s390x: Add z14 support

* Add support for processor features (including auto-detection).

* Move base architecture set requirement back to z14.

* Add z15 feature sets and re-enable z15-specific code generation
  when required features are available.

cranelift/codegen/meta/src/isa/s390x/mod.rs

@@ -3,13 +3,50 @@ use crate::cdsl::instructions::{InstructionGroupBuilder, InstructionPredicateMap
 use crate::cdsl::isa::TargetIsa;
 use crate::cdsl::recipes::Recipes;
 use crate::cdsl::regs::IsaRegsBuilder;
-use crate::cdsl::settings::SettingGroupBuilder;
+use crate::cdsl::settings::{SettingGroup, SettingGroupBuilder};
 
 use crate::shared::Definitions as SharedDefinitions;
 
+fn define_settings(_shared: &SettingGroup) -> SettingGroup {
+    let mut settings = SettingGroupBuilder::new("s390x");
+
+    // The baseline architecture for cranelift is z14 (arch12),
+    // so we list only facilities of later processors here.
+
+    // z15 (arch13) facilities
+    let has_mie2 = settings.add_bool(
+        "has_mie2",
+        "Has Miscellaneous-Instruction-Extensions Facility 2 support.",
+        "",
+        false,
+    );
+    let has_vxrs_ext2 = settings.add_bool(
+        "has_vxrs_ext2",
+        "Has Vector-Enhancements Facility 2 support.",
+        "",
+        false,
+    );
+
+    // Architecture level presets
+    settings.add_preset(
+        "arch13",
+        "Thirteenth Edition of the z/Architecture.",
+        preset!(has_mie2 && has_vxrs_ext2),
+    );
+
+    // Processor presets
+    settings.add_preset(
+        "z15",
+        "IBM z15 processor.",
+        preset!(has_mie2 && has_vxrs_ext2),
+    );
+
+    settings.build()
+}
+
 pub(crate) fn define(shared_defs: &mut SharedDefinitions) -> TargetIsa {
     let inst_group = InstructionGroupBuilder::new(&mut shared_defs.all_instructions).build();
-    let settings = SettingGroupBuilder::new("s390x").build();
+    let settings = define_settings(&shared_defs.settings);
     let regs = IsaRegsBuilder::new().build();
     let recipes = Recipes::new();
     let encodings_predicates = InstructionPredicateMap::new();