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/src/isa/x86/enc_tables.rs

@@ -1288,3 +1288,40 @@ fn convert_ineg(
         unreachable!()
     }
 }
+
+fn expand_tls_value(
+    inst: ir::Inst,
+    func: &mut ir::Function,
+    _cfg: &mut ControlFlowGraph,
+    isa: &dyn TargetIsa,
+) {
+    use crate::settings::TlsModel;
+
+    assert!(
+        isa.triple().architecture == target_lexicon::Architecture::X86_64,
+        "Not yet implemented for {:?}",
+        isa.triple(),
+    );
+
+    if let ir::InstructionData::UnaryGlobalValue {
+        opcode: ir::Opcode::TlsValue,
+        global_value,
+    } = func.dfg[inst]
+    {
+        let ctrl_typevar = func.dfg.ctrl_typevar(inst);
+        assert_eq!(ctrl_typevar, ir::types::I64);
+
+        match isa.flags().tls_model() {
+            TlsModel::None => panic!("tls_model flag is not set."),
+            TlsModel::ElfGd => {
+                func.dfg.replace(inst).x86_elf_tls_get_addr(global_value);
+            }
+            TlsModel::Macho => {
+                func.dfg.replace(inst).x86_macho_tls_get_addr(global_value);
+            }
+            model => unimplemented!("tls_value for tls model {:?}", model),
+        }
+    } else {
+        unreachable!();
+    }
+}