Add TLS support for ELF and MachO (#1174)

* Add TLS support
* Add binemit and legalize tests
* Spill all caller-saved registers when necessary

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

@@ -1127,6 +1127,18 @@ pub(crate) fn define(
         .operands_out(vec![a]),
     );
 
+    ig.push(
+        Inst::new(
+            "tls_value",
+            r#"
+        Compute the value of global GV, which is a TLS (thread local storage) value.
+        "#,
+            &formats.unary_global_value,
+        )
+        .operands_in(vec![GV])
+        .operands_out(vec![a]),
+    );
+
     let HeapOffset = &TypeVar::new(
         "HeapOffset",
         "An unsigned heap offset",

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

@@ -1,6 +1,6 @@
 //! Shared definitions for the Cranelift intermediate language.
 
-mod entities;
+pub mod entities;
 pub mod formats;
 pub mod immediates;
 pub mod instructions;
@@ -28,6 +28,7 @@ pub(crate) struct Definitions {
     pub imm: Immediates,
     pub formats: Formats,
     pub transform_groups: TransformGroups,
+    pub entities: EntityRefs,
 }
 
 pub(crate) fn define() -> Definitions {
@@ -47,6 +48,7 @@ pub(crate) fn define() -> Definitions {
         imm: immediates,
         formats,
         transform_groups,
+        entities,
     }
 }
 

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

@@ -131,6 +131,14 @@ pub(crate) fn define() -> SettingGroup {
         false,
     );
 
+    settings.add_enum(
+        "tls_model",
+        r#"
+            Defines the model used to perform TLS accesses.
+        "#,
+        vec!["none", "elf_gd", "macho", "coff"],
+    );
+
     // Settings specific to the `baldrdash` calling convention.
 
     settings.add_enum(