Add support for parallel linking in IL2CPP builds

action.yml

@@ -43,6 +43,10 @@ inputs:
     required: false
     default: ''
     description: 'Launches unity without specifying `-nographics`.'
+  enableParallelLinking:
+    required: false
+    default: 'true'
+    description: 'Enable parallel linking for IL2CPP builds to speed up linking phase.'
   customParameters:
     required: false
     default: ''

dist/default-build-script/Assets/Editor/UnityBuilderAction/Builder.cs

@@ -116,6 +116,12 @@ public static void BuildProject()
           AndroidSettings.Apply(options);
         }
 
+        // Enable parallel linking for IL2CPP builds
+        if (options.TryGetValue("enableParallelLinking", out var enableParallelLinking) && 
+            enableParallelLinking != "false") {
+          SetParallelLinking(buildTarget);
+        }
+
       }
 
       // Perform build
@@ -129,5 +135,47 @@ public static void BuildProject()
       BuildResult result = summary.result;
       StdOutReporter.ExitWithResult(result);
     }
+
+    private static void SetParallelLinking(BuildTarget buildTarget) {
+      string additionalArgs = PlayerSettings.additionalIl2CppArgs;
+
+      // Determine number of parallel jobs (use CPU count, or default to 4)
+      int numJobs = System.Environment.ProcessorCount;
+      if (numJobs <= 0) numJobs = 2;
+
+      // Platform-specific parallel linking flags
+      switch (buildTarget) {
+        case BuildTarget.StandaloneWindows:
+        case BuildTarget.StandaloneWindows64:
+          string cgthreadsFlag = $"--linker-flags=/CGTHREADS:{numJobs}";
+          if (!additionalArgs.Contains("/CGTHREADS:")) {
+            additionalArgs = string.IsNullOrEmpty(additionalArgs) 
+              ? cgthreadsFlag 
+              : $"{additionalArgs} {cgthreadsFlag}";
+          }
+          break;
+
+        case BuildTarget.StandaloneLinux64:
+        case BuildTarget.Android:
+        case BuildTarget.iOS:
+          if (!additionalArgs.Contains("--threads")) {
+            additionalArgs = string.IsNullOrEmpty(additionalArgs)
+              ? $"-Wl,--threads={numJobs}"
+              : $"{additionalArgs} -Wl,--threads={numJobs}";
+          }
+          break;
+
+        case BuildTarget.StandaloneOSX:
+          if (!additionalArgs.Contains("thread_count")) {
+            additionalArgs = string.IsNullOrEmpty(additionalArgs)
+              ? $"-Wl,-thread_count,{numJobs}"
+              : $"{additionalArgs} -Wl,-thread_count,{numJobs}";
+          }
+          break;
+      }
+
+      PlayerSettings.additionalIl2CppArgs = additionalArgs;
+      Debug.Log($"IL2CPP parallel linking enabled with {numJobs} jobs. Additional args: {additionalArgs}");
+    }
   }
 }

dist/platforms/mac/steps/build.sh

@@ -166,6 +166,7 @@ echo ""
   -androidTargetSdkVersion "$ANDROID_TARGET_SDK_VERSION" \
   -androidExportType "$ANDROID_EXPORT_TYPE" \
   -androidSymbolType "$ANDROID_SYMBOL_TYPE" \
+  $( [ "${ENABLE_PARALLEL_LINKING}" == "true" ] && echo "-enableParallelLinking" ) \
   $CUSTOM_PARAMETERS
 
 # Catch exit code

dist/platforms/ubuntu/steps/build.sh

@@ -140,6 +140,7 @@ unity-editor \
   -androidTargetSdkVersion "$ANDROID_TARGET_SDK_VERSION" \
   -androidExportType "$ANDROID_EXPORT_TYPE" \
   -androidSymbolType "$ANDROID_SYMBOL_TYPE" \
+  $( [ "${ENABLE_PARALLEL_LINKING}" == "true" ] && echo "-enableParallelLinking" ) \
   $CUSTOM_PARAMETERS
 
 # Catch exit code

dist/platforms/windows/build.ps1

@@ -178,7 +178,11 @@ $unityArgs = @(
     "-androidExportType", "`"$Env:ANDROID_EXPORT_TYPE`"",
     "-androidSymbolType", "`"$Env:ANDROID_SYMBOL_TYPE`"",
     "-logfile", "-"
-) + $customParametersArray
+)
+if ($Env:ENABLE_PARALLEL_LINKING -eq "true") {
+    $unityArgs += @("-enableParallelLinking")
+}
+$unityArgs = $unityArgs + $customParametersArray
 
 if (-not $Env:BUILD_PROFILE) {
     $unityArgs += @("-buildTarget", "`"$Env:BUILD_TARGET`"")

src/model/build-parameters.ts

@@ -34,6 +34,7 @@ class BuildParameters {
   public buildVersion!: string;
   public manualExit!: boolean;
   public enableGpu!: boolean;
+  public enableParallelLinking!: boolean;
   public androidVersionCode!: string;
   public androidKeystoreName!: string;
   public androidKeystoreBase64!: string;
@@ -162,6 +163,7 @@ class BuildParameters {
       buildVersion,
       manualExit: Input.manualExit,
       enableGpu: Input.enableGpu,
+      enableParallelLinking: Input.enableParallelLinking,
       androidVersionCode,
       androidKeystoreName: Input.androidKeystoreName,
       androidKeystoreBase64: Input.androidKeystoreBase64,

src/model/image-environment-factory.ts

@@ -44,6 +44,7 @@ class ImageEnvironmentFactory {
       { name: 'BUILD_METHOD', value: parameters.buildMethod },
       { name: 'MANUAL_EXIT', value: parameters.manualExit },
       { name: 'ENABLE_GPU', value: parameters.enableGpu },
+      { name: 'ENABLE_PARALLEL_LINKING', value: parameters.enableParallelLinking },
       { name: 'VERSION', value: parameters.buildVersion },
       { name: 'ANDROID_VERSION_CODE', value: parameters.androidVersionCode },
       { name: 'ANDROID_KEYSTORE_NAME', value: parameters.androidKeystoreName },

src/model/input.ts

@@ -143,6 +143,12 @@ class Input {
     return input === 'true';
   }
 
+  static get enableParallelLinking(): boolean {
+    const input = Input.getInput('enableParallelLinking') ?? true;
+
+    return input === 'true';
+  }
+
   static get customParameters(): string {
     return Input.getInput('customParameters') ?? '';
   }

src/model/platform-setup/setup-mac.ts

@@ -194,6 +194,7 @@ class SetupMac {
     process.env.CHOWN_FILES_TO = buildParameters.chownFilesTo;
     process.env.MANUAL_EXIT = buildParameters.manualExit.toString();
     process.env.ENABLE_GPU = buildParameters.enableGpu.toString();
+    process.env.ENABLE_PARALLEL_LINKING = buildParameters.enableParallelLinking.toString();
   }
 }