Add TLS support for ELF and MachO (#1174)

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

cranelift/filetests/filetests/isa/x86/tls_elf.clif

@@ -0,0 +1,18 @@
+test regalloc
+set tls_model=elf_gd
+target x86_64
+
+function u0:0(i32) -> i32, i64 {
+gv0 = symbol colocated tls u1:0
+
+block0(v0: i32):
+    ; check: block0(v2: i32 [%rdi]):
+    ; nextln: [RexOp1spillSib32#89,ss0]           v0 = spill v2
+    v1 = global_value.i64 gv0
+    ; nextln: [elf_tls_get_addr#00,%rax]          v1 = x86_elf_tls_get_addr gv0
+    ; nextln: [RexOp1fillSib32#8b,%r15]           v3 = fill v0
+    return v0, v1
+    ; nextln: [RexOp1rmov#8089]                   regmove v1, %rax -> %rdx
+    ; nextln: [RexOp1rmov#89]                     regmove v3, %r15 -> %rax
+    ; nextln: [Op1ret#c3]                         return v3, v1
+}

cranelift/filetests/filetests/isa/x86/tls_enc.clif

@@ -0,0 +1,11 @@
+test binemit
+target x86_64
+
+function u0:0() -> i64, i64 {
+gv0 = symbol colocated tls u1:0
+
+block0:
+    [-, %rax] v0 = x86_elf_tls_get_addr gv0 ; bin: 66 48 8d 3d ElfX86_64TlsGd(u1:0-4) 00000000 66 66 48 e8 CallPLTRel4(%ElfTlsGetAddr-4) 00000000
+    [-, %rax] v1 = x86_macho_tls_get_addr gv0; bin: 48 8b 3d MachOX86_64Tlv(u1:0-4) 00000000 ff 17
+    return v0, v1
+}

cranelift/filetests/filetests/isa/x86/tls_macho.clif

@@ -0,0 +1,18 @@
+test regalloc
+set tls_model=macho
+target x86_64
+
+function u0:0(i32) -> i32, i64 {
+gv0 = symbol colocated tls u1:0
+
+block0(v0: i32):
+    ; check: block0(v2: i32 [%rdi]):
+    ; nextln: [RexOp1spillSib32#89,ss0]           v0 = spill v2
+    v1 = global_value.i64 gv0
+    ; nextln: [macho_tls_get_addr#00,%rax]        v1 = x86_macho_tls_get_addr gv0
+    ; nextln: [RexOp1fillSib32#8b,%r15]           v3 = fill v0
+    return v0, v1
+    ; nextln: [RexOp1rmov#8089]                   regmove v1, %rax -> %rdx
+    ; nextln: [RexOp1rmov#89]                     regmove v3, %r15 -> %rax
+    ; nextln: [Op1ret#c3]                         return v3, v1
+}