Add support for toc optimization in soong

Skip relinking against shared libraries whose interface hasn't changed.

Test: mmma -j frameworks/native/libs/gui
Test: touch frameworks/native/libs/gui/BufferItem.cpp
Test: mmma -j frameworks/native/libs/gui, see nothing relinks past libgui
Bug: 26014946
Change-Id: I4d4b8da6a35c682341ae51869f5c72b51e192053

cc/binary.go

@@ -281,6 +281,9 @@ func (binary *binaryDecorator) link(ctx ModuleContext,
 			flagsToBuilderFlags(flags), afterPrefixSymbols)
 	}
 
+	linkerDeps = append(linkerDeps, deps.SharedLibsDeps...)
+	linkerDeps = append(linkerDeps, deps.LateSharedLibsDeps...)
+
 	TransformObjToDynamicBinary(ctx, objFiles, sharedLibs, deps.StaticLibs,
 		deps.LateStaticLibs, deps.WholeStaticLibs, linkerDeps, deps.CrtBegin, deps.CrtEnd, true,
 		builderFlags, outputFile)

cc/builder.go

@@ -138,6 +138,18 @@ var (
 			Description: "copy gcc $out",
 		},
 		"ccCmd", "cFlags", "libName")
+
+	tocPath = pctx.SourcePathVariable("tocPath", "build/soong/scripts/toc.sh")
+
+	toc = pctx.AndroidStaticRule("toc",
+		blueprint.RuleParams{
+			Depfile:     "${out}.d",
+			Deps:        blueprint.DepsGCC,
+			Command:     "CROSS_COMPILE=$crossCompile $tocPath -i ${in} -o ${out} -d ${out}.d",
+			CommandDeps: []string{"$tocPath"},
+			Restat:      true,
+		},
+		"crossCompile")
 )
 
 func init() {
@@ -380,7 +392,6 @@ func TransformObjToDynamicBinary(ctx android.ModuleContext,
 		libFlagsList = append(libFlagsList, lib.String())
 	}
 
-	deps = append(deps, sharedLibs...)
 	deps = append(deps, staticLibs...)
 	deps = append(deps, lateStaticLibs...)
 	deps = append(deps, wholeStaticLibs...)
@@ -403,6 +414,22 @@ func TransformObjToDynamicBinary(ctx android.ModuleContext,
 	})
 }
 
+// Generate a rule for extract a table of contents from a shared library (.so)
+func TransformSharedObjectToToc(ctx android.ModuleContext, inputFile android.WritablePath,
+	outputFile android.WritablePath, flags builderFlags) {
+
+	crossCompile := gccCmd(flags.toolchain, "")
+
+	ctx.ModuleBuild(pctx, android.ModuleBuildParams{
+		Rule:   toc,
+		Output: outputFile,
+		Input:  inputFile,
+		Args: map[string]string{
+			"crossCompile": crossCompile,
+		},
+	})
+}
+
 // Generate a rule for compiling multiple .o files to a .o using ld partial linking
 func TransformObjsToObj(ctx android.ModuleContext, objFiles android.Paths,
 	flags builderFlags, outputFile android.WritablePath) {

cc/cc.go

@@ -70,18 +70,25 @@ type Deps struct {
 }
 
 type PathDeps struct {
+	// Paths to .so files
 	SharedLibs, LateSharedLibs android.Paths
+	// Paths to the dependencies to use for .so files (.so.toc files)
+	SharedLibsDeps, LateSharedLibsDeps android.Paths
+	// Paths to .a files
 	StaticLibs, LateStaticLibs, WholeStaticLibs android.Paths
 
+	// Paths to .o files
 	ObjFiles               android.Paths
 	WholeStaticLibObjFiles android.Paths
 
+	// Paths to generated source files
 	GeneratedSources android.Paths
 	GeneratedHeaders android.Paths
 
 	Flags, ReexportedFlags []string
 	ReexportedFlagsDeps    android.Paths
 
+	// Paths to crt*.o files
 	CrtBegin, CrtEnd android.OptionalPath
 }
 
@@ -815,19 +822,27 @@ func (c *Module) depsToPaths(ctx android.ModuleContext) PathDeps {
 			checkLinkType(c, cc)
 		}
 
+		var ptr *android.Paths
 		var depPtr *android.Paths
 
+		linkFile := cc.outputFile
+		depFile := android.OptionalPath{}
+
 		switch tag {
 		case ndkStubDepTag, sharedDepTag, sharedExportDepTag:
-			depPtr = &depPaths.SharedLibs
+			ptr = &depPaths.SharedLibs
+			depPtr = &depPaths.SharedLibsDeps
+			depFile = cc.linker.(libraryInterface).toc()
 		case lateSharedDepTag, ndkLateStubDepTag:
-			depPtr = &depPaths.LateSharedLibs
+			ptr = &depPaths.LateSharedLibs
+			depPtr = &depPaths.LateSharedLibsDeps
+			depFile = cc.linker.(libraryInterface).toc()
 		case staticDepTag, staticExportDepTag:
-			depPtr = &depPaths.StaticLibs
+			ptr = &depPaths.StaticLibs
 		case lateStaticDepTag:
-			depPtr = &depPaths.LateStaticLibs
+			ptr = &depPaths.LateStaticLibs
 		case wholeStaticDepTag:
-			depPtr = &depPaths.WholeStaticLibs
+			ptr = &depPaths.WholeStaticLibs
 			staticLib, ok := cc.linker.(libraryInterface)
 			if !ok || !staticLib.static() {
 				ctx.ModuleErrorf("module %q not a static library", name)
@@ -844,17 +859,25 @@ func (c *Module) depsToPaths(ctx android.ModuleContext) PathDeps {
 			depPaths.WholeStaticLibObjFiles =
 				append(depPaths.WholeStaticLibObjFiles, staticLib.objs()...)
 		case objDepTag:
-			depPtr = &depPaths.ObjFiles
+			ptr = &depPaths.ObjFiles
 		case crtBeginDepTag:
-			depPaths.CrtBegin = cc.outputFile
+			depPaths.CrtBegin = linkFile
 		case crtEndDepTag:
-			depPaths.CrtEnd = cc.outputFile
+			depPaths.CrtEnd = linkFile
 		default:
 			panic(fmt.Errorf("unknown dependency tag: %s", tag))
 		}
 
+		if ptr != nil {
+			*ptr = append(*ptr, linkFile.Path())
+		}
+
 		if depPtr != nil {
-			*depPtr = append(*depPtr, cc.outputFile.Path())
+			dep := depFile
+			if !dep.Valid() {
+				dep = linkFile
+			}
+			*depPtr = append(*depPtr, dep.Path())
 		}
 	})
 

cc/library.go

@@ -18,6 +18,7 @@ import (
 	"strings"
 
 	"github.com/google/blueprint"
+	"github.com/google/blueprint/pathtools"
 
 	"android/soong"
 	"android/soong/android"
@@ -158,6 +159,8 @@ type libraryDecorator struct {
 
 	// For reusing static library objects for shared library
 	reuseObjFiles android.Paths
+	// table-of-contents file to optimize out relinking when possible
+	tocFile android.OptionalPath
 
 	flagExporter
 	stripper
@@ -269,6 +272,7 @@ type libraryInterface interface {
 	static() bool
 	objs() android.Paths
 	reuseObjs() android.Paths
+	toc() android.OptionalPath
 
 	// Returns true if the build options for the module have selected a static or shared build
 	buildStatic() bool
@@ -434,10 +438,28 @@ func (library *libraryDecorator) linkShared(ctx ModuleContext,
 		}
 	}
 
+	linkerDeps = append(linkerDeps, deps.SharedLibsDeps...)
+	linkerDeps = append(linkerDeps, deps.LateSharedLibsDeps...)
+
 	TransformObjToDynamicBinary(ctx, objFiles, sharedLibs,
 		deps.StaticLibs, deps.LateStaticLibs, deps.WholeStaticLibs,
 		linkerDeps, deps.CrtBegin, deps.CrtEnd, false, builderFlags, outputFile)
 
+	if ctx.Device() {
+		// For device targets, optimize out relinking against shared
+		// libraries whose interface hasn't changed by depending on
+		// a table of contents file instead of the library itself.
+		// For host targets, the library might be part of a host tool
+		// that is run during the build, use the library directly so
+		// that the timestamp of the binary changes whenever a library
+		// changes and any necessary tools get re-run.
+		tocPath := outputFile.String()
+		tocPath = pathtools.ReplaceExtension(tocPath, flags.Toolchain.ShlibSuffix()[1:]+".toc")
+		tocFile := android.PathForOutput(ctx, tocPath)
+		library.tocFile = android.OptionalPathForPath(tocFile)
+		TransformSharedObjectToToc(ctx, outputFile, tocFile, builderFlags)
+	}
+
 	return ret
 }
 
@@ -482,6 +504,10 @@ func (library *libraryDecorator) reuseObjs() android.Paths {
 	return library.reuseObjFiles
 }
 
+func (library *libraryDecorator) toc() android.OptionalPath {
+	return library.tocFile
+}
+
 func (library *libraryDecorator) install(ctx ModuleContext, file android.Path) {
 	if !ctx.static() {
 		library.baseInstaller.install(ctx, file)

scripts/strip.sh

@@ -5,6 +5,7 @@
 #  Environment:
 #   CROSS_COMPILE: prefix added to readelf, objcopy tools
 #  Arguments:
+#   -i ${file}: input file (required)
 #   -o ${file}: output file (required)
 #   -d ${file}: deps file (required)
 #   --keep-symbols

scripts/toc.sh

@@ -0,0 +1,75 @@
+#!/bin/bash -eu
+
+# Script to handle generating a .toc file from a .so file
+# Inputs:
+#  Environment:
+#   CROSS_COMPILE: prefix added to readelf tool
+#  Arguments:
+#   -i ${file}: input file (required)
+#   -o ${file}: output file (required)
+#   -d ${file}: deps file (required)
+
+OPTSTRING=d:i:o:-:
+
+usage() {
+    cat <<EOF
+Usage: toc.sh [options] -i in-file -o out-file -d deps-file
+Options:
+EOF
+    exit 1
+}
+
+do_elf() {
+    ("${CROSS_COMPILE}readelf" -d "${infile}" | grep SONAME || echo "No SONAME for ${infile}") > "${outfile}.tmp"
+    "${CROSS_COMPILE}readelf" --dyn-syms "${infile}" | awk '{$2=""; $3=""; print}' >> "${outfile}.tmp"
+}
+
+do_macho() {
+    otool -l "${infile}" | grep LC_ID_DYLIB -A 5 > "${outfile}.tmp"
+    nm -gP "${infile}" | cut -f1-2 -d" " | grep -v 'U$' >> "${outfile}.tmp"
+}
+
+
+while getopts $OPTSTRING opt; do
+    case "$opt" in
+        d) depsfile="${OPTARG}" ;;
+        i) infile="${OPTARG}" ;;
+        o) outfile="${OPTARG}" ;;
+        -)
+            case "${OPTARG}" in
+                *) echo "Unknown option --${OPTARG}"; usage ;;
+            esac;;
+        ?) usage ;;
+        *) echo "'${opt}' '${OPTARG}'"
+    esac
+done
+
+if [ -z "${infile}" ]; then
+    echo "-i argument is required"
+    usage
+fi
+
+if [ -z "${outfile}" ]; then
+    echo "-o argument is required"
+    usage
+fi
+
+if [ -z "${depsfile}" ]; then
+    echo "-d argument is required"
+    usage
+fi
+
+rm -f "${outfile}.tmp"
+
+cat <<EOF > "${depsfile}"
+${outfile}: \\
+  ${CROSS_COMPILE}readelf \\
+EOF
+
+do_elf
+
+if cmp "${outfile}" "${outfile}.tmp" > /dev/null 2> /dev/null; then
+    rm -f "${outfile}.tmp"
+else
+    mv -f "${outfile}.tmp" "${outfile}"
+fi