cranelift: Remove the enable_simd shared setting

This commit removes a setting for Cranelift which I've found a bit
confusing historically and I think is no longer necessary. The setting
is currently documented as enabling SIMD instructions, but that only
sort of works for the x64 backend and none of the other backends look at
it. Historically this was used to flag to Cranelift that a higher x64
baseline feature set is required for codegen but as of bytecodealliance#6625 that's no
longer necessary.

Otherwise it seems more Cranelift-like nowadays to say that vector
instructions generate SIMD instructions where non-vector instructions
probably don't, but may still depending on activated CPU features. In
that sense I'm not sure if a dedicated `enable_simd` setting is still
motivated, so this PR removes it.

This renames some features in the x86 backend such as `use_avx_simd` to
`use_avx` since the `_simd` part is no longer part of the computation
now that `enable_simd` is gone.

cranelift/codegen/meta/src/cdsl/settings.rs

@@ -142,17 +142,6 @@ impl SettingGroup {
         let num_predicates = self.num_bool_settings() + (self.predicates.len() as u8);
         self.bool_start_byte_offset + (num_predicates + 7) / 8
     }
-
-    pub fn get_bool(&self, name: &'static str) -> (BoolSettingIndex, &Self) {
-        for (i, s) in self.settings.iter().enumerate() {
-            if let SpecificSetting::Bool(_) = s.specific {
-                if s.name == name {
-                    return (BoolSettingIndex(i), self);
-                }
-            }
-        }
-        panic!("Should have found bool setting by name.");
-    }
 }
 
 /// This is the basic information needed to track the specific parts of a setting when building

cranelift/codegen/meta/src/isa/x86.rs

@@ -3,13 +3,13 @@ use crate::cdsl::settings::{PredicateNode, SettingGroup, SettingGroupBuilder};
 
 use crate::shared::Definitions as SharedDefinitions;
 
-pub(crate) fn define(shared_defs: &mut SharedDefinitions) -> TargetIsa {
-    let settings = define_settings(&shared_defs.settings);
+pub(crate) fn define(_shared_defs: &mut SharedDefinitions) -> TargetIsa {
+    let settings = define_settings();
 
     TargetIsa::new("x86", settings)
 }
 
-fn define_settings(shared: &SettingGroup) -> SettingGroup {
+fn define_settings() -> SettingGroup {
     let mut settings = SettingGroupBuilder::new("x86");
 
     // CPUID.01H:ECX
@@ -114,51 +114,18 @@ fn define_settings(shared: &SettingGroup) -> SettingGroup {
         false,
     );
 
-    let shared_enable_simd = shared.get_bool("enable_simd");
-
     settings.add_predicate("use_ssse3", predicate!(has_ssse3));
     settings.add_predicate("use_sse41", predicate!(has_sse41));
     settings.add_predicate("use_sse42", predicate!(has_sse41 && has_sse42));
     settings.add_predicate("use_fma", predicate!(has_avx && has_fma));
 
-    settings.add_predicate(
-        "use_ssse3_simd",
-        predicate!(shared_enable_simd && has_ssse3),
-    );
-    settings.add_predicate(
-        "use_sse41_simd",
-        predicate!(shared_enable_simd && has_sse41),
-    );
-    settings.add_predicate(
-        "use_sse42_simd",
-        predicate!(shared_enable_simd && has_sse41 && has_sse42),
-    );
-
-    settings.add_predicate("use_avx_simd", predicate!(shared_enable_simd && has_avx));
-    settings.add_predicate(
-        "use_avx2_simd",
-        predicate!(shared_enable_simd && has_avx && has_avx2),
-    );
-    settings.add_predicate(
-        "use_avx512bitalg_simd",
-        predicate!(shared_enable_simd && has_avx512bitalg),
-    );
-    settings.add_predicate(
-        "use_avx512dq_simd",
-        predicate!(shared_enable_simd && has_avx512dq),
-    );
-    settings.add_predicate(
-        "use_avx512vl_simd",
-        predicate!(shared_enable_simd && has_avx512vl),
-    );
-    settings.add_predicate(
-        "use_avx512vbmi_simd",
-        predicate!(shared_enable_simd && has_avx512vbmi),
-    );
-    settings.add_predicate(
-        "use_avx512f_simd",
-        predicate!(shared_enable_simd && has_avx512f),
-    );
+    settings.add_predicate("use_avx", predicate!(has_avx));
+    settings.add_predicate("use_avx2", predicate!(has_avx && has_avx2));
+    settings.add_predicate("use_avx512bitalg", predicate!(has_avx512bitalg));
+    settings.add_predicate("use_avx512dq", predicate!(has_avx512dq));
+    settings.add_predicate("use_avx512vl", predicate!(has_avx512vl));
+    settings.add_predicate("use_avx512vbmi", predicate!(has_avx512vbmi));
+    settings.add_predicate("use_avx512f", predicate!(has_avx512f));
 
     settings.add_predicate("use_popcnt", predicate!(has_popcnt && has_sse42));
     settings.add_predicate("use_bmi1", predicate!(has_bmi1));

cranelift/codegen/meta/src/shared/settings.rs

@@ -115,13 +115,6 @@ pub(crate) fn define() -> SettingGroup {
         false,
     );
 
-    settings.add_bool(
-        "enable_simd",
-        "Enable the use of SIMD instructions.",
-        "",
-        false,
-    );
-
     settings.add_bool(
         "enable_atomics",
         "Enable the use of atomic instructions",