From 6db4d4e61369da479734dc5fdfb40638f5c984f9 Mon Sep 17 00:00:00 2001
From: Colin Cross <ccross@android.com>
Date: Thu, 21 Feb 2019 14:58:58 -0800
Subject: [PATCH] Optimize CPU time when running d8 and r8

Pass -XX:+TieredCompilation -XX:TieredStopAtLevel=1 to the JVM to
reduce the time spent JITing, which in local experiments reduced
the CPU time of R8 while increasing the wall time, and reduced the
total number of runnable threads.

Without the new flags:
$ time out/soong/host/linux-x86/bin/r8-compat-proguard -injars out/target/common/obj/APPS/Dialer_intermediates/classes.jar ...
real	0m30.090s
user	4m35.337s
sys	0m12.853s

With the new flags:
$ time out/soong/host/linux-x86/bin/r8-compat-proguard -JXX:+TieredCompilation -JXX:TieredStopAtLevel=1 -injars out/target/common/obj/APPS/Dialer_intermediates/classes.jar ...
real	0m35.674s
user	2m45.135s
sys	0m9.531s

The increase in wall time should be offset by the better parallelism from
the reduced CPU time.

Bug: 119270658
Test: m checkbuild
Change-Id: I8fc78b5ef1f8c6f51fd97a29461b96ae2b35cada
---
 java/config/config.go   | 1 +
 java/config/makevars.go | 2 ++
 java/dex.go             | 4 ++--
 3 files changed, 5 insertions(+), 2 deletions(-)

diff --git a/java/config/config.go b/java/config/config.go
index 7cc249cbc..e607b1d55 100644
--- a/java/config/config.go
+++ b/java/config/config.go
@@ -61,6 +61,7 @@ func init() {
 
 	pctx.StaticVariable("JavacHeapSize", "2048M")
 	pctx.StaticVariable("JavacHeapFlags", "-J-Xmx${JavacHeapSize}")
+	pctx.StaticVariable("DexFlags", "-JXX:+TieredCompilation -JXX:TieredStopAtLevel=1")
 
 	pctx.StaticVariable("CommonJdkFlags", strings.Join([]string{
 		`-Xmaxerrs 9999999`,
diff --git a/java/config/makevars.go b/java/config/makevars.go
index 156ee2638..30552da06 100644
--- a/java/config/makevars.go
+++ b/java/config/makevars.go
@@ -81,4 +81,6 @@ func makeVarsProvider(ctx android.MakeVarsContext) {
 
 	ctx.Strict("CLASS2GREYLIST", "${Class2Greylist}")
 	ctx.Strict("HIDDENAPI", "${HiddenAPI}")
+
+	ctx.Strict("DEX_FLAGS", "${DexFlags}")
 }
diff --git a/java/dex.go b/java/dex.go
index 54b7bfcfb..987129ee7 100644
--- a/java/dex.go
+++ b/java/dex.go
@@ -25,7 +25,7 @@ import (
 var d8 = pctx.AndroidStaticRule("d8",
 	blueprint.RuleParams{
 		Command: `rm -rf "$outDir" && mkdir -p "$outDir" && ` +
-			`${config.D8Cmd} --output $outDir $d8Flags $in && ` +
+			`${config.D8Cmd} ${config.DexFlags} --output $outDir $d8Flags $in && ` +
 			`${config.SoongZipCmd} $zipFlags -o $outDir/classes.dex.jar -C $outDir -f "$outDir/classes*.dex" && ` +
 			`${config.MergeZipsCmd} -D -stripFile "**/*.class" $out $outDir/classes.dex.jar $in`,
 		CommandDeps: []string{
@@ -40,7 +40,7 @@ var r8 = pctx.AndroidStaticRule("r8",
 	blueprint.RuleParams{
 		Command: `rm -rf "$outDir" && mkdir -p "$outDir" && ` +
 			`rm -f "$outDict" && ` +
-			`${config.R8Cmd} -injars $in --output $outDir ` +
+			`${config.R8Cmd} ${config.DexFlags} -injars $in --output $outDir ` +
 			`--force-proguard-compatibility ` +
 			`--no-data-resources ` +
 			`-printmapping $outDict ` +