diff --git a/java/bootclasspath_fragment.go b/java/bootclasspath_fragment.go
index 34735c2..b183651 100644
--- a/java/bootclasspath_fragment.go
+++ b/java/bootclasspath_fragment.go
@@ -843,12 +843,12 @@
 	return b.testFragment
 }
 
-// produceHiddenAPIOutput produces the hidden API all-flags.csv file (and supporting files)
-// for the fragment as well as encoding the flags in the boot dex jars.
-func (b *BootclasspathFragmentModule) produceHiddenAPIOutput(ctx android.ModuleContext, contents []android.Module, input HiddenAPIFlagInput) *HiddenAPIOutput {
+// generateHiddenApiFlagRules generates rules to generate hidden API flags and compute the signature
+// patterns file.
+func (b *BootclasspathFragmentModule) generateHiddenApiFlagRules(ctx android.ModuleContext, contents []android.Module, input HiddenAPIFlagInput, bootDexInfoByModule bootDexInfoByModule, suffix string) HiddenAPIFlagOutput {
 	// Generate the rules to create the hidden API flags and update the supplied hiddenAPIInfo with the
 	// paths to the created files.
-	output := hiddenAPIRulesForBootclasspathFragment(ctx, contents, input)
+	flagOutput := hiddenAPIFlagRulesForBootclasspathFragment(ctx, bootDexInfoByModule, contents, input)
 
 	// If the module specifies split_packages or package_prefixes then use those to generate the
 	// signature patterns.
@@ -856,8 +856,8 @@
 	packagePrefixes := input.PackagePrefixes
 	singlePackages := input.SinglePackages
 	if splitPackages != nil || packagePrefixes != nil || singlePackages != nil {
-		output.SignaturePatternsPath = buildRuleSignaturePatternsFile(
-			ctx, output.AllFlagsPath, splitPackages, packagePrefixes, singlePackages)
+		flagOutput.SignaturePatternsPath = buildRuleSignaturePatternsFile(
+			ctx, flagOutput.AllFlagsPath, splitPackages, packagePrefixes, singlePackages)
 	} else if !b.isTestFragment() {
 		ctx.ModuleErrorf(`Must specify at least one of the split_packages, package_prefixes and single_packages properties
   If this is a new bootclasspath_fragment or you are unsure what to do add the
@@ -869,6 +869,26 @@
   should specify here. If you are happy with its suggestions then you can add
   the --fix option and it will fix them for you.`, b.BaseModuleName())
 	}
+	return flagOutput
+}
+
+// produceHiddenAPIOutput produces the hidden API all-flags.csv file (and supporting files)
+// for the fragment as well as encoding the flags in the boot dex jars.
+func (b *BootclasspathFragmentModule) produceHiddenAPIOutput(ctx android.ModuleContext, contents []android.Module, input HiddenAPIFlagInput) *HiddenAPIOutput {
+	// Gather information about the boot dex files for the boot libraries provided by this fragment.
+	bootDexInfoByModule := extractBootDexInfoFromModules(ctx, contents)
+
+	// Generate the flag file needed to encode into the dex files.
+	flagOutput := b.generateHiddenApiFlagRules(ctx, contents, input, bootDexInfoByModule, "")
+
+	// Encode those flags into the dex files of the contents of this fragment.
+	encodedBootDexFilesByModule := hiddenAPIEncodeRulesForBootclasspathFragment(ctx, bootDexInfoByModule, flagOutput.AllFlagsPath)
+
+	// Store that information for return for use by other rules.
+	output := &HiddenAPIOutput{
+		HiddenAPIFlagOutput:         flagOutput,
+		EncodedBootDexFilesByModule: encodedBootDexFilesByModule,
+	}
 
 	return output
 }
diff --git a/java/hiddenapi_modular.go b/java/hiddenapi_modular.go
index 7b67803..08e684c 100644
--- a/java/hiddenapi_modular.go
+++ b/java/hiddenapi_modular.go
@@ -1116,8 +1116,8 @@
 	return validFile
 }
 
-// hiddenAPIRulesForBootclasspathFragment will generate all the flags for a fragment of the
-// bootclasspath and then encode the flags into the boot dex files.
+// hiddenAPIFlagRulesForBootclasspathFragment will generate all the flags for a fragment of the
+// bootclasspath.
 //
 // It takes:
 // * Map from android.SdkKind to stub dex jar paths defining the API for that sdk kind.
@@ -1130,13 +1130,9 @@
 // * metadata.csv
 // * index.csv
 // * all-flags.csv
-// * encoded boot dex files
-func hiddenAPIRulesForBootclasspathFragment(ctx android.ModuleContext, contents []android.Module, input HiddenAPIFlagInput) *HiddenAPIOutput {
+func hiddenAPIFlagRulesForBootclasspathFragment(ctx android.ModuleContext, bootDexInfoByModule bootDexInfoByModule, contents []android.Module, input HiddenAPIFlagInput) HiddenAPIFlagOutput {
 	hiddenApiSubDir := "modular-hiddenapi"
 
-	// Gather information about the boot dex files for the boot libraries provided by this fragment.
-	bootDexInfoByModule := extractBootDexInfoFromModules(ctx, contents)
-
 	// Generate the stub-flags.csv.
 	stubFlagsCSV := android.PathForModuleOut(ctx, hiddenApiSubDir, "stub-flags.csv")
 	buildRuleToGenerateHiddenAPIStubFlagsFile(ctx, "modularHiddenAPIStubFlagsFile", "modular hiddenapi stub flags", stubFlagsCSV, bootDexInfoByModule.bootDexJars(), input, nil)
@@ -1169,16 +1165,6 @@
 	allFlagsCSV := android.PathForModuleOut(ctx, hiddenApiSubDir, "all-flags.csv")
 	buildRuleToGenerateHiddenApiFlags(ctx, "modularHiddenApiAllFlags", "modular hiddenapi all flags", allFlagsCSV, stubFlagsCSV, android.Paths{annotationFlagsCSV}, input.FlagFilesByCategory, nil, removedDexSignatures)
 
-	// Encode the flags into the boot dex files.
-	encodedBootDexJarsByModule := map[string]android.Path{}
-	outputDir := android.PathForModuleOut(ctx, "hiddenapi-modular/encoded").OutputPath
-	for _, name := range android.SortedStringKeys(bootDexInfoByModule) {
-		bootDexInfo := bootDexInfoByModule[name]
-		unencodedDex := bootDexInfo.path
-		encodedDex := hiddenAPIEncodeDex(ctx, unencodedDex, allFlagsCSV, bootDexInfo.uncompressDex, bootDexInfo.minSdkVersion, outputDir)
-		encodedBootDexJarsByModule[name] = encodedDex
-	}
-
 	// Generate the filtered-stub-flags.csv file which contains the filtered stub flags that will be
 	// compared against the monolithic stub flags.
 	filteredStubFlagsCSV := android.PathForModuleOut(ctx, hiddenApiSubDir, "filtered-stub-flags.csv")
@@ -1194,19 +1180,30 @@
 		HIDDENAPI_FLAGS_CSV_IMPL_FLAGS)
 
 	// Store the paths in the info for use by other modules and sdk snapshot generation.
-	output := HiddenAPIOutput{
-		HiddenAPIFlagOutput: HiddenAPIFlagOutput{
-			AnnotationFlagsPath:   annotationFlagsCSV,
-			MetadataPath:          metadataCSV,
-			IndexPath:             indexCSV,
-			StubFlagsPath:         stubFlagsCSV,
-			AllFlagsPath:          allFlagsCSV,
-			FilteredStubFlagsPath: filteredStubFlagsCSV,
-			FilteredFlagsPath:     filteredFlagsCSV,
-		},
-		EncodedBootDexFilesByModule: encodedBootDexJarsByModule,
+	return HiddenAPIFlagOutput{
+		AnnotationFlagsPath:   annotationFlagsCSV,
+		MetadataPath:          metadataCSV,
+		IndexPath:             indexCSV,
+		StubFlagsPath:         stubFlagsCSV,
+		AllFlagsPath:          allFlagsCSV,
+		FilteredStubFlagsPath: filteredStubFlagsCSV,
+		FilteredFlagsPath:     filteredFlagsCSV,
 	}
-	return &output
+}
+
+// hiddenAPIEncodeRulesForBootclasspathFragment generates rules to encode hidden API flags into the
+// dex jars in bootDexInfoByModule.
+func hiddenAPIEncodeRulesForBootclasspathFragment(ctx android.ModuleContext, bootDexInfoByModule bootDexInfoByModule, allFlagsCSV android.Path) bootDexJarByModule {
+	// Encode the flags into the boot dex files.
+	encodedBootDexJarsByModule := bootDexJarByModule{}
+	outputDir := android.PathForModuleOut(ctx, "hiddenapi-modular/encoded").OutputPath
+	for _, name := range android.SortedStringKeys(bootDexInfoByModule) {
+		bootDexInfo := bootDexInfoByModule[name]
+		unencodedDex := bootDexInfo.path
+		encodedDex := hiddenAPIEncodeDex(ctx, unencodedDex, allFlagsCSV, bootDexInfo.uncompressDex, bootDexInfo.minSdkVersion, outputDir)
+		encodedBootDexJarsByModule[name] = encodedDex
+	}
+	return encodedBootDexJarsByModule
 }
 
 func buildRuleToGenerateRemovedDexSignatures(ctx android.ModuleContext, removedTxtFiles android.Paths) android.OptionalPath {