Allow remote execution of link actions.

This CL adds a remoteexec package that allows adding a configurable RBE
prefix to the template.

Test: built aosp crosshatch userdebug with and without RBE_CXX_LINKS.
Change-Id: Ica920c3d7f79f2996210b9cbd448126451c1707c

cc/builder.go

@@ -29,6 +29,7 @@ import (
 
 	"android/soong/android"
 	"android/soong/cc/config"
+	"android/soong/remoteexec"
 )
 
 const (
@@ -62,7 +63,7 @@ var (
 		},
 		"ccCmd", "cFlags")
 
-	ld = pctx.AndroidStaticRule("ld",
+	ld, ldRE = remoteexec.StaticRules(pctx, "ld",
 		blueprint.RuleParams{
 			Command: "$ldCmd ${crtBegin} @${out}.rsp " +
 				"${libFlags} ${crtEnd} -o ${out} ${ldFlags} ${extraLibFlags}",
@@ -72,16 +73,28 @@ var (
 			// clang -Wl,--out-implib doesn't update its output file if it hasn't changed.
 			Restat: true,
 		},
-		"ldCmd", "crtBegin", "libFlags", "crtEnd", "ldFlags", "extraLibFlags")
+		&remoteexec.REParams{Labels: map[string]string{"type": "link", "tool": "clang"},
+			ExecStrategy:    "${config.RECXXLinksExecStrategy}",
+			Inputs:          []string{"${out}.rsp"},
+			RSPFile:         "${out}.rsp",
+			OutputFiles:     []string{"${out}"},
+			ToolchainInputs: []string{"$ldCmd"},
+			Platform:        map[string]string{remoteexec.PoolKey: "${config.RECXXLinksPool}"},
+		}, []string{"ldCmd", "crtBegin", "libFlags", "crtEnd", "ldFlags", "extraLibFlags"}, nil)
 
-	partialLd = pctx.AndroidStaticRule("partialLd",
+	partialLd, partialLdRE = remoteexec.StaticRules(pctx, "partialLd",
 		blueprint.RuleParams{
 			// Without -no-pie, clang 7.0 adds -pie to link Android files,
 			// but -r and -pie cannot be used together.
 			Command:     "$ldCmd -fuse-ld=lld -nostdlib -no-pie -Wl,-r ${in} -o ${out} ${ldFlags}",
 			CommandDeps: []string{"$ldCmd"},
-		},
-		"ldCmd", "ldFlags")
+		}, &remoteexec.REParams{
+			Labels:       map[string]string{"type": "link", "tool": "clang"},
+			ExecStrategy: "${config.RECXXLinksExecStrategy}", Inputs: []string{"$inCommaList"},
+			OutputFiles:     []string{"${out}"},
+			ToolchainInputs: []string{"$ldCmd"},
+			Platform:        map[string]string{remoteexec.PoolKey: "${config.RECXXLinksPool}"},
+		}, []string{"ldCmd", "ldFlags"}, []string{"inCommaList"})
 
 	ar = pctx.AndroidStaticRule("ar",
 		blueprint.RuleParams{
@@ -262,6 +275,7 @@ func init() {
 	}
 
 	pctx.HostBinToolVariable("SoongZipCmd", "soong_zip")
+	pctx.Import("android/soong/remoteexec")
 }
 
 type builderFlags struct {
@@ -657,8 +671,13 @@ func TransformObjToDynamicBinary(ctx android.ModuleContext,
 		deps = append(deps, crtBegin.Path(), crtEnd.Path())
 	}
 
+	rule := ld
+	if ctx.Config().IsEnvTrue("RBE_CXX_LINKS") {
+		rule = ldRE
+	}
+
 	ctx.Build(pctx, android.BuildParams{
-		Rule:            ld,
+		Rule:            rule,
 		Description:     "link " + outputFile.Base(),
 		Output:          outputFile,
 		ImplicitOutputs: implicitOutputs,
@@ -798,16 +817,22 @@ func TransformObjsToObj(ctx android.ModuleContext, objFiles android.Paths,
 
 	ldCmd := "${config.ClangBin}/clang++"
 
+	rule := partialLd
+	args := map[string]string{
+		"ldCmd":   ldCmd,
+		"ldFlags": flags.globalLdFlags + " " + flags.localLdFlags,
+	}
+	if ctx.Config().IsEnvTrue("RBE_CXX_LINKS") {
+		rule = partialLdRE
+		args["inCommaList"] = strings.Join(objFiles.Strings(), ",")
+	}
 	ctx.Build(pctx, android.BuildParams{
-		Rule:        partialLd,
+		Rule:        rule,
 		Description: "link " + outputFile.Base(),
 		Output:      outputFile,
 		Inputs:      objFiles,
 		Implicits:   deps,
-		Args: map[string]string{
-			"ldCmd":   ldCmd,
-			"ldFlags": flags.globalLdFlags + " " + flags.localLdFlags,
-		},
+		Args:        args,
 	})
 }
 

cc/config/global.go

@@ -18,6 +18,7 @@ import (
 	"strings"
 
 	"android/soong/android"
+	"android/soong/remoteexec"
 )
 
 var (
@@ -255,6 +256,9 @@ func init() {
 		}
 		return ""
 	})
+
+	pctx.VariableFunc("RECXXLinksPool", envOverrideFunc("RBE_CXX_LINKS_POOL", remoteexec.DefaultPool))
+	pctx.VariableFunc("RECXXLinksExecStrategy", envOverrideFunc("RBE_CXX_LINKS_EXEC_STRATEGY", remoteexec.LocalExecStrategy))
 }
 
 var HostPrebuiltTag = pctx.VariableConfigMethod("HostPrebuiltTag", android.Config.PrebuiltOS)
@@ -268,3 +272,12 @@ func bionicHeaders(kernelArch string) string {
 		"-isystem bionic/libc/kernel/android/uapi",
 	}, " ")
 }
+
+func envOverrideFunc(envVar, defaultVal string) func(ctx android.PackageVarContext) string {
+	return func(ctx android.PackageVarContext) string {
+		if override := ctx.Config().Getenv(envVar); override != "" {
+			return override
+		}
+		return defaultVal
+	}
+}