2 files changed, 33 insertions, 1 deletions
diff --git a/src/main/java/com/google/devtools/build/lib/rules/apple/AppleCommandLineOptions.java b/src/main/java/com/google/devtools/build/lib/rules/apple/AppleCommandLineOptions.java
index 612d2b3e3a..bba468d3a2 100644
--- a/src/main/java/com/google/devtools/build/lib/rules/apple/AppleCommandLineOptions.java
+++ b/src/main/java/com/google/devtools/build/lib/rules/apple/AppleCommandLineOptions.java
@@ -15,6 +15,7 @@
 package com.google.devtools.build.lib.rules.apple;
 
 import com.google.common.annotations.VisibleForTesting;
+import com.google.common.base.Strings;
 import com.google.common.collect.ImmutableList;
 import com.google.common.collect.Multimap;
 import com.google.devtools.build.lib.analysis.config.BuildConfiguration.DefaultLabelConverter;
@@ -286,6 +287,34 @@ public class AppleCommandLineOptions extends FragmentOptions {
     return Platform.forTarget(PlatformType.IOS, iosCpu);
   }
 
+  /**
+   * Returns the architecture implied by these options.
+   *
+   * <p> In contexts in which a configuration instance is present, prefer
+   * {@link AppleConfiguration#getSingleArchitecture}.
+   */
+  public String getSingleArchitecture() {
+    if (!Strings.isNullOrEmpty(appleSplitCpu)) {
+      return appleSplitCpu;
+    }
+    switch (applePlatformType) {
+      case IOS:
+        if (!iosMultiCpus.isEmpty()) {
+          return iosMultiCpus.get(0);
+        } else {
+          return iosCpu;
+        }
+      case WATCHOS:
+        return watchosCpus.get(0);
+      case TVOS:
+        return tvosCpus.get(0);
+      case MACOS:
+        return macosCpus.get(0);
+      default:
+        throw new IllegalArgumentException("Unhandled platform type " + applePlatformType);
+    }
+  }
+
   @Override
   public void addAllLabels(Multimap<String, Label> labelMap) {
     if (getPlatform() == Platform.IOS_DEVICE) {
diff --git a/src/main/java/com/google/devtools/build/lib/rules/objc/AppleCrosstoolTransition.java b/src/main/java/com/google/devtools/build/lib/rules/objc/AppleCrosstoolTransition.java
index 953329563c..38c79dd84a 100644
--- a/src/main/java/com/google/devtools/build/lib/rules/objc/AppleCrosstoolTransition.java
+++ b/src/main/java/com/google/devtools/build/lib/rules/objc/AppleCrosstoolTransition.java
@@ -53,7 +53,10 @@ public class AppleCrosstoolTransition implements PatchTransition {
 
     // TODO(b/29355778): Once ios_cpu is retired, introduce another top-level flag (perhaps
     // --apple_cpu) for toolchain selection in top-level consuming rules.
-    String cpu = "ios_" + buildOptions.get(AppleCommandLineOptions.class).iosCpu;
+    String cpu = String.format("%s_%s",
+        buildOptions.get(AppleCommandLineOptions.class).applePlatformType,
+        buildOptions.get(AppleCommandLineOptions.class).getSingleArchitecture());
+
     setAppleCrosstoolTransitionConfiguration(buildOptions, result, cpu);
     return result;
   }