Bazel 3.7.1 patch to build an arm64 slice targeting the iOS Simulator. Use it by running `bazel build ... --cpu=ios_sim_arm64 --apple_platform_type=ios`

ios_sim_arm64.patch

diff --git a/src/main/java/com/google/devtools/build/lib/rules/apple/ApplePlatform.java b/src/main/java/com/google/devtools/build/lib/rules/apple/ApplePlatform.java
index 7759984b03..6f41eca83b 100644
--- a/src/main/java/com/google/devtools/build/lib/rules/apple/ApplePlatform.java
+++ b/src/main/java/com/google/devtools/build/lib/rules/apple/ApplePlatform.java
@@ -42,7 +42,7 @@ public enum ApplePlatform implements ApplePlatformApi {
   CATALYST("catalyst", "MacOSX", PlatformType.CATALYST, true);
 
   private static final ImmutableSet<String> IOS_SIMULATOR_TARGET_CPUS =
-      ImmutableSet.of("ios_x86_64", "ios_i386");
+      ImmutableSet.of("ios_x86_64", "ios_i386", "ios_sim_arm64");
   private static final ImmutableSet<String> IOS_DEVICE_TARGET_CPUS =
       ImmutableSet.of("ios_armv6", "ios_arm64", "ios_armv7", "ios_armv7s", "ios_arm64e");
   private static final ImmutableSet<String> WATCHOS_SIMULATOR_TARGET_CPUS =
diff --git a/tools/osx/crosstool/cc_toolchain_config.bzl b/tools/osx/crosstool/cc_toolchain_config.bzl
index 6ca6b8ef0c..d490b2ce1a 100644
--- a/tools/osx/crosstool/cc_toolchain_config.bzl
+++ b/tools/osx/crosstool/cc_toolchain_config.bzl
@@ -63,6 +63,8 @@ def _impl(ctx):
         toolchain_identifier = "darwin_arm64e"
     elif (ctx.attr.cpu == "ios_arm64"):
         toolchain_identifier = "ios_arm64"
+    elif (ctx.attr.cpu == "ios_sim_arm64"):
+        toolchain_identifier = "ios_sim_arm64"
     elif (ctx.attr.cpu == "ios_arm64e"):
         toolchain_identifier = "ios_arm64e"
     elif (ctx.attr.cpu == "ios_armv7"):
@@ -94,6 +96,7 @@ def _impl(ctx):
           ctx.attr.cpu == "darwin_arm64" or
           ctx.attr.cpu == "darwin_arm64e" or
           ctx.attr.cpu == "ios_arm64" or
+          ctx.attr.cpu == "ios_sim_arm64" or
           ctx.attr.cpu == "ios_arm64e" or
           ctx.attr.cpu == "ios_armv7" or
           ctx.attr.cpu == "ios_i386" or
@@ -110,6 +113,8 @@ def _impl(ctx):
 
     if (ctx.attr.cpu == "ios_arm64"):
         target_system_name = "arm64-apple-ios"
+    elif (ctx.attr.cpu == "ios_sim_arm64"):
+        target_system_name = "arm64-apple-ios-simulator"
     elif (ctx.attr.cpu == "tvos_arm64"):
         target_system_name = "arm64-apple-tvos"
     elif (ctx.attr.cpu == "watchos_arm64_32"):
@@ -151,6 +156,8 @@ def _impl(ctx):
         target_cpu = "darwin_arm64e"
     elif (ctx.attr.cpu == "ios_arm64"):
         target_cpu = "ios_arm64"
+    elif (ctx.attr.cpu == "ios_sim_arm64"):
+        target_cpu = "ios_sim_arm64"
     elif (ctx.attr.cpu == "ios_arm64e"):
         target_cpu = "ios_arm64e"
     elif (ctx.attr.cpu == "ios_armv7"):
@@ -177,6 +184,7 @@ def _impl(ctx):
     if (ctx.attr.cpu == "armeabi-v7a"):
         target_libc = "armeabi-v7a"
     elif (ctx.attr.cpu == "ios_arm64" or
+          ctx.attr.cpu == "ios_sim_arm64" or
           ctx.attr.cpu == "ios_arm64e" or
           ctx.attr.cpu == "ios_armv7" or
           ctx.attr.cpu == "ios_i386" or
@@ -206,6 +214,7 @@ def _impl(ctx):
     elif (ctx.attr.cpu == "darwin_arm64" or
           ctx.attr.cpu == "darwin_arm64e" or
           ctx.attr.cpu == "ios_arm64" or
+          ctx.attr.cpu == "ios_sim_arm64" or
           ctx.attr.cpu == "ios_arm64e" or
           ctx.attr.cpu == "ios_armv7" or
           ctx.attr.cpu == "ios_i386" or
@@ -227,6 +236,7 @@ def _impl(ctx):
     elif (ctx.attr.cpu == "darwin_arm64" or
           ctx.attr.cpu == "darwin_arm64e" or
           ctx.attr.cpu == "ios_arm64" or
+          ctx.attr.cpu == "ios_sim_arm64" or
           ctx.attr.cpu == "ios_arm64e" or
           ctx.attr.cpu == "ios_armv7" or
           ctx.attr.cpu == "ios_i386" or
@@ -343,6 +353,7 @@ def _impl(ctx):
           ctx.attr.cpu == "darwin_arm64" or
           ctx.attr.cpu == "darwin_arm64e" or
           ctx.attr.cpu == "ios_arm64" or
+          ctx.attr.cpu == "ios_sim_arm64" or
           ctx.attr.cpu == "ios_arm64e" or
           ctx.attr.cpu == "ios_armv7" or
           ctx.attr.cpu == "ios_i386" or
@@ -474,6 +485,39 @@ def _impl(ctx):
                 ),
             ],
         )
+    elif (ctx.attr.cpu == "ios_sim_arm64"):
+        objc_compile_action = action_config(
+            action_name = ACTION_NAMES.objc_compile,
+            flag_sets = [
+                flag_set(
+                    flag_groups = [flag_group(flags = ["-arch", "arm64"])],
+                ),
+            ],
+            implies = [
+                "compiler_input_flags",
+                "compiler_output_flags",
+                "objc_actions",
+                "apply_default_compiler_flags",
+                "apply_default_warnings",
+                "framework_paths",
+                "preprocessor_defines",
+                "include_system_dirs",
+                "version_min",
+                "objc_arc",
+                "no_objc_arc",
+                "apple_env",
+                "user_compile_flags",
+                "sysroot",
+                "unfiltered_compile_flags",
+                "apply_simulator_compiler_flags",
+            ],
+            tools = [
+                tool(
+                    path = "wrapped_clang",
+                    execution_requirements = xcode_execution_requirements,
+                ),
+            ],
+        )
     elif (ctx.attr.cpu == "ios_arm64e" or
           ctx.attr.cpu == "darwin_arm64e"):
         objc_compile_action = action_config(
@@ -800,6 +844,7 @@ def _impl(ctx):
             ],
         )
     elif (ctx.attr.cpu == "ios_arm64" or
+          ctx.attr.cpu == "ios_sim_arm64" or
           ctx.attr.cpu == "tvos_arm64" or
           ctx.attr.cpu == "darwin_arm64"):
         objcpp_executable_action = action_config(
@@ -1213,6 +1258,7 @@ def _impl(ctx):
           ctx.attr.cpu == "darwin_arm64" or
           ctx.attr.cpu == "darwin_arm64e" or
           ctx.attr.cpu == "ios_arm64" or
+          ctx.attr.cpu == "ios_sim_arm64" or
           ctx.attr.cpu == "ios_arm64e" or
           ctx.attr.cpu == "ios_armv7" or
           ctx.attr.cpu == "ios_i386" or
@@ -1295,6 +1341,7 @@ def _impl(ctx):
           ctx.attr.cpu == "darwin_arm64" or
           ctx.attr.cpu == "darwin_arm64e" or
           ctx.attr.cpu == "ios_arm64" or
+          ctx.attr.cpu == "ios_sim_arm64" or
           ctx.attr.cpu == "ios_arm64e" or
           ctx.attr.cpu == "ios_armv7" or
           ctx.attr.cpu == "ios_i386" or
@@ -1358,6 +1405,7 @@ def _impl(ctx):
           ctx.attr.cpu == "darwin_arm64" or
           ctx.attr.cpu == "darwin_arm64e" or
           ctx.attr.cpu == "ios_arm64" or
+          ctx.attr.cpu == "ios_sim_arm64" or
           ctx.attr.cpu == "ios_arm64e" or
           ctx.attr.cpu == "ios_armv7" or
           ctx.attr.cpu == "ios_i386" or
@@ -1472,6 +1520,7 @@ def _impl(ctx):
             ],
         )
     elif (ctx.attr.cpu == "ios_arm64" or
+          ctx.attr.cpu == "ios_sim_arm64" or
           ctx.attr.cpu == "tvos_arm64" or
           ctx.attr.cpu == "darwin_arm64"):
         objcpp_compile_action = action_config(
@@ -1755,6 +1804,7 @@ def _impl(ctx):
           ctx.attr.cpu == "darwin_arm64" or
           ctx.attr.cpu == "darwin_arm64e" or
           ctx.attr.cpu == "ios_arm64" or
+          ctx.attr.cpu == "ios_sim_arm64" or
           ctx.attr.cpu == "ios_arm64e" or
           ctx.attr.cpu == "ios_armv7" or
           ctx.attr.cpu == "ios_i386" or
@@ -1816,6 +1866,7 @@ def _impl(ctx):
           ctx.attr.cpu == "darwin_arm64" or
           ctx.attr.cpu == "darwin_arm64e" or
           ctx.attr.cpu == "ios_arm64" or
+          ctx.attr.cpu == "ios_sim_arm64" or
           ctx.attr.cpu == "ios_arm64e" or
           ctx.attr.cpu == "ios_armv7" or
           ctx.attr.cpu == "ios_i386" or
@@ -1912,6 +1963,7 @@ def _impl(ctx):
             ],
         )
     elif (ctx.attr.cpu == "ios_arm64" or
+          ctx.attr.cpu == "ios_sim_arm64" or
           ctx.attr.cpu == "tvos_arm64" or
           ctx.attr.cpu == "darwin_arm64"):
         objc_archive_action = action_config(
@@ -2240,6 +2292,7 @@ def _impl(ctx):
             ],
         )
     elif (ctx.attr.cpu == "ios_arm64" or
+          ctx.attr.cpu == "ios_sim_arm64" or
           ctx.attr.cpu == "tvos_arm64" or
           ctx.attr.cpu == "darwin_arm64"):
         objc_executable_action = action_config(
@@ -2676,6 +2729,7 @@ def _impl(ctx):
           ctx.attr.cpu == "darwin_arm64" or
           ctx.attr.cpu == "darwin_arm64e" or
           ctx.attr.cpu == "ios_arm64" or
+          ctx.attr.cpu == "ios_sim_arm64" or
           ctx.attr.cpu == "ios_arm64e" or
           ctx.attr.cpu == "ios_armv7" or
           ctx.attr.cpu == "ios_i386" or
@@ -2763,6 +2817,7 @@ def _impl(ctx):
           ctx.attr.cpu == "darwin_arm64" or
           ctx.attr.cpu == "darwin_arm64e" or
           ctx.attr.cpu == "ios_arm64" or
+          ctx.attr.cpu == "ios_sim_arm64" or
           ctx.attr.cpu == "ios_arm64e" or
           ctx.attr.cpu == "ios_armv7" or
           ctx.attr.cpu == "ios_i386" or
@@ -2828,6 +2883,7 @@ def _impl(ctx):
           ctx.attr.cpu == "darwin_arm64" or
           ctx.attr.cpu == "darwin_arm64e" or
           ctx.attr.cpu == "ios_arm64" or
+          ctx.attr.cpu == "ios_sim_arm64" or
           ctx.attr.cpu == "ios_arm64e" or
           ctx.attr.cpu == "ios_armv7" or
           ctx.attr.cpu == "ios_i386" or
@@ -2946,6 +3002,7 @@ def _impl(ctx):
             ],
         )
     elif (ctx.attr.cpu == "ios_arm64" or
+          ctx.attr.cpu == "ios_sim_arm64" or
           ctx.attr.cpu == "tvos_arm64"):
         objc_fully_link_action = action_config(
             action_name = "objc-fully-link",
@@ -3211,6 +3268,7 @@ def _impl(ctx):
           ctx.attr.cpu == "darwin_arm64" or
           ctx.attr.cpu == "darwin_arm64e" or
           ctx.attr.cpu == "ios_arm64" or
+          ctx.attr.cpu == "ios_sim_arm64" or
           ctx.attr.cpu == "ios_arm64e" or
           ctx.attr.cpu == "ios_armv7" or
           ctx.attr.cpu == "ios_i386" or
@@ -3253,6 +3311,7 @@ def _impl(ctx):
 
     if (ctx.attr.cpu == "armeabi-v7a" or
         ctx.attr.cpu == "ios_arm64" or
+        ctx.attr.cpu == "ios_sim_arm64" or
         ctx.attr.cpu == "ios_arm64e" or
         ctx.attr.cpu == "ios_armv7" or
         ctx.attr.cpu == "ios_i386" or
@@ -3409,6 +3468,7 @@ def _impl(ctx):
           ctx.attr.cpu == "darwin_arm64" or
           ctx.attr.cpu == "darwin_arm64e" or
           ctx.attr.cpu == "ios_arm64" or
+          ctx.attr.cpu == "ios_sim_arm64" or
           ctx.attr.cpu == "ios_arm64e" or
           ctx.attr.cpu == "ios_armv7" or
           ctx.attr.cpu == "ios_i386" or
@@ -3504,6 +3564,7 @@ def _impl(ctx):
           ctx.attr.cpu == "darwin_arm64" or
           ctx.attr.cpu == "darwin_arm64e" or
           ctx.attr.cpu == "ios_arm64" or
+          ctx.attr.cpu == "ios_sim_arm64" or
           ctx.attr.cpu == "ios_arm64e" or
           ctx.attr.cpu == "ios_armv7" or
           ctx.attr.cpu == "tvos_arm64" or
@@ -3554,6 +3615,7 @@ def _impl(ctx):
 
     if (ctx.attr.cpu == "armeabi-v7a" or
         ctx.attr.cpu == "ios_arm64" or
+        ctx.attr.cpu == "ios_sim_arm64" or
         ctx.attr.cpu == "ios_arm64e" or
         ctx.attr.cpu == "ios_armv7" or
         ctx.attr.cpu == "ios_i386" or
@@ -3681,6 +3743,26 @@ def _impl(ctx):
                 ),
             ],
         )
+    elif (ctx.attr.cpu == "ios_sim_arm64"):
+        default_link_flags_feature = feature(
+            name = "default_link_flags",
+            enabled = True,
+            flag_sets = [
+                flag_set(
+                    actions = all_link_actions +
+                              ["objc-executable", "objc++-executable"],
+                    flag_groups = [
+                        flag_group(
+                            flags = [
+                                "-no-canonical-prefixes",
+                                "-target",
+                                "arm64-apple-ios-simulator",
+                            ],
+                        ),
+                    ],
+                ),
+            ],
+        )
     elif (ctx.attr.cpu == "tvos_arm64"):
         default_link_flags_feature = feature(
             name = "default_link_flags",
@@ -4051,7 +4133,8 @@ def _impl(ctx):
         # This stub doesn't have a sensible value for this feature
         version_min_feature = feature(name = "version_min")
     elif (ctx.attr.cpu == "ios_i386" or
-          ctx.attr.cpu == "ios_x86_64"):
+          ctx.attr.cpu == "ios_x86_64" or
+          ctx.attr.cpu == "ios_sim_arm64"):
         version_min_feature = feature(
             name = "version_min",
             flag_sets = [
@@ -4562,6 +4645,7 @@ def _impl(ctx):
 
     if (ctx.attr.cpu == "armeabi-v7a" or
         ctx.attr.cpu == "ios_arm64" or
+        ctx.attr.cpu == "ios_sim_arm64" or
         ctx.attr.cpu == "ios_arm64e" or
         ctx.attr.cpu == "ios_armv7" or
         ctx.attr.cpu == "ios_i386" or
@@ -4789,6 +4873,37 @@ def _impl(ctx):
                 ),
             ],
         )
+    elif (ctx.attr.cpu == "ios_sim_arm64"):
+        unfiltered_compile_flags_feature = feature(
+            name = "unfiltered_compile_flags",
+            flag_sets = [
+                flag_set(
+                    actions = [
+                        ACTION_NAMES.assemble,
+                        ACTION_NAMES.preprocess_assemble,
+                        ACTION_NAMES.c_compile,
+                        ACTION_NAMES.cpp_compile,
+                        ACTION_NAMES.cpp_header_parsing,
+                        ACTION_NAMES.cpp_module_compile,
+                        ACTION_NAMES.cpp_module_codegen,
+                        ACTION_NAMES.linkstamp_compile,
+                    ],
+                    flag_groups = [
+                        flag_group(
+                            flags = [
+                                "-no-canonical-prefixes",
+                                "-Wno-builtin-macro-redefined",
+                                "-D__DATE__=\"redacted\"",
+                                "-D__TIMESTAMP__=\"redacted\"",
+                                "-D__TIME__=\"redacted\"",
+                                "-target",
+                                "arm64-apple-ios-simulator",
+                            ],
+                        ),
+                    ],
+                ),
+            ],
+        )
     elif (ctx.attr.cpu == "tvos_arm64"):
         unfiltered_compile_flags_feature = feature(
             name = "unfiltered_compile_flags",
@@ -5322,6 +5437,7 @@ def _impl(ctx):
           ctx.attr.cpu == "darwin_arm64" or
           ctx.attr.cpu == "darwin_arm64e" or
           ctx.attr.cpu == "ios_arm64" or
+          ctx.attr.cpu == "ios_sim_arm64" or
           ctx.attr.cpu == "ios_arm64e" or
           ctx.attr.cpu == "ios_armv7" or
           ctx.attr.cpu == "ios_i386" or
@@ -5530,6 +5646,7 @@ def _impl(ctx):
           ctx.attr.cpu == "darwin_arm64" or
           ctx.attr.cpu == "darwin_arm64e" or
           ctx.attr.cpu == "ios_arm64" or
+          ctx.attr.cpu == "ios_sim_arm64" or
           ctx.attr.cpu == "ios_armv7" or
           ctx.attr.cpu == "ios_i386" or
           ctx.attr.cpu == "ios_x86_64" or
@@ -5741,6 +5858,7 @@ def _impl(ctx):
     elif (ctx.attr.cpu == "armeabi-v7a" or
           ctx.attr.cpu == "darwin_arm64" or
           ctx.attr.cpu == "ios_arm64" or
+          ctx.attr.cpu == "ios_sim_arm64" or
           ctx.attr.cpu == "ios_arm64e" or
           ctx.attr.cpu == "ios_armv7" or
           ctx.attr.cpu == "ios_i386" or
@@ -5872,6 +5990,7 @@ def _impl(ctx):
         )
     elif (ctx.attr.cpu == "armeabi-v7a" or
           ctx.attr.cpu == "ios_arm64" or
+          ctx.attr.cpu == "ios_sim_arm64" or
           ctx.attr.cpu == "ios_arm64e" or
           ctx.attr.cpu == "ios_armv7" or
           ctx.attr.cpu == "ios_i386" or
@@ -5932,6 +6051,7 @@ def _impl(ctx):
     )
 
     if (ctx.attr.cpu == "ios_arm64" or
+        ctx.attr.cpu == "ios_sim_arm64" or
         ctx.attr.cpu == "ios_arm64e" or
         ctx.attr.cpu == "ios_armv7" or
         ctx.attr.cpu == "tvos_arm64" or
@@ -6024,6 +6144,7 @@ def _impl(ctx):
     )
 
     if (ctx.attr.cpu == "ios_arm64" or
+        ctx.attr.cpu == "ios_sim_arm64" or
         ctx.attr.cpu == "ios_arm64e" or
         ctx.attr.cpu == "ios_armv7" or
         ctx.attr.cpu == "ios_i386" or
@@ -6288,6 +6409,7 @@ def _impl(ctx):
           ctx.attr.cpu == "darwin_arm64" or
           ctx.attr.cpu == "darwin_arm64e" or
           ctx.attr.cpu == "ios_arm64" or
+          ctx.attr.cpu == "ios_sim_arm64" or
           ctx.attr.cpu == "ios_arm64e" or
           ctx.attr.cpu == "ios_armv7" or
           ctx.attr.cpu == "ios_i386" or
diff --git a/tools/osx/crosstool/osx_archs.bzl b/tools/osx/crosstool/osx_archs.bzl
index 14fad06a5f..97a0baa19a 100644
--- a/tools/osx/crosstool/osx_archs.bzl
+++ b/tools/osx/crosstool/osx_archs.bzl
@@ -20,6 +20,7 @@ OSX_TOOLS_NON_DEVICE_ARCHS = [
     "darwin_arm64e",
     "ios_i386",
     "ios_x86_64",
+    "ios_sim_arm64",
     "watchos_i386",
     "watchos_x86_64",
     "tvos_x86_64",
@@ -50,6 +51,7 @@ OSX_TOOLS_CONSTRAINTS = {
     "armeabi-v7a": ["@platforms//cpu:arm"],
     "ios_armv7": ["@platforms//os:ios", "@platforms//cpu:arm"],
     "ios_arm64": ["@platforms//os:ios", "@platforms//cpu:aarch64"],
+    "ios_sim_arm64": ["@platforms//os:ios", "@platforms//cpu:aarch64"],
     "ios_arm64e": ["@platforms//os:ios", "@platforms//cpu:aarch64"],
     "watchos_armv7k": ["@platforms//os:ios", "@platforms//cpu:arm"],
     "watchos_arm64_32": ["@platforms//os:ios", "@platforms//cpu:aarch64"],

looking at bazel:master today, has your ios_sim_arm64 been implemented as ios_arm64e?

Something like this is finally starting to land upstream, here's the updated version of a change like this bazelbuild/bazel#13870