Support 128-bit atomics on all x86_64 Apple targets

Author: taiki-e

compiler/rustc_target/src/spec/x86_64_apple_ios.rs

@@ -13,7 +13,7 @@ pub fn target() -> Target {
             .into(),
         arch: arch.target_arch(),
         options: TargetOptions {
-            max_atomic_width: Some(64),
+            max_atomic_width: Some(128),
             stack_probes: StackProbeType::X86,
             ..base
         },

compiler/rustc_target/src/spec/x86_64_apple_ios_macabi.rs

@@ -15,7 +15,7 @@ pub fn target() -> Target {
             .into(),
         arch: arch.target_arch(),
         options: TargetOptions {
-            max_atomic_width: Some(64),
+            max_atomic_width: Some(128),
             stack_probes: StackProbeType::X86,
             ..base
         },

compiler/rustc_target/src/spec/x86_64_apple_tvos.rs

@@ -9,7 +9,7 @@ pub fn target() -> Target {
         data_layout: "e-m:o-i64:64-f80:128-n8:16:32:64-S128".into(),
         arch: arch.target_arch(),
         options: TargetOptions {
-            max_atomic_width: Some(64),
+            max_atomic_width: Some(128),
             stack_probes: StackProbeType::X86,
             ..opts("tvos", arch)
         },

compiler/rustc_target/src/spec/x86_64_apple_watchos_sim.rs

@@ -10,7 +10,7 @@ pub fn target() -> Target {
             .into(),
         arch: arch.target_arch(),
         options: TargetOptions {
-            max_atomic_width: Some(64),
+            max_atomic_width: Some(128),
             stack_probes: StackProbeType::X86,
             forces_embed_bitcode: true,
             // Taken from a clang build on Xcode 11.4.1.