From 7e53c57ed6a42dc096971270797e888fefe206a8 Mon Sep 17 00:00:00 2001
From: Yi Kong <yikong@google.com>
Date: Wed, 14 Feb 2018 18:16:12 +0800
Subject: [PATCH] Disable inlining and loop unrolling in LTO without PGO
 profile

Such optimisations may significantly increase the binary size when
compiler heuristics are off. Disabling these helps cut down the
binary sizes with negligible decrease in performance, but allows us to
be more comfortable enabling LTO across various projects.

Test: m
Test: dex2oat, hwui, skia benchmark
Bug: 62839002
Change-Id: Id63e8dd295df2972f76ae4e29ee367080fff8429
---
 cc/cc.go  | 12 ++++++++++++
 cc/lto.go |  7 +++++++
 cc/pgo.go | 11 +++++++++--
 3 files changed, 28 insertions(+), 2 deletions(-)

diff --git a/cc/cc.go b/cc/cc.go
index 49fefe965..f65441fa6 100644
--- a/cc/cc.go
+++ b/cc/cc.go
@@ -211,6 +211,7 @@ type ModuleContextIntf interface {
 	selectedStl() string
 	baseModuleName() string
 	getVndkExtendsModuleName() string
+	isPgoCompile() bool
 }
 
 type ModuleContext interface {
@@ -408,6 +409,13 @@ func (c *Module) isVndk() bool {
 	return false
 }
 
+func (c *Module) isPgoCompile() bool {
+	if pgo := c.pgo; pgo != nil {
+		return pgo.Properties.PgoCompile
+	}
+	return false
+}
+
 func (c *Module) isVndkSp() bool {
 	if vndkdep := c.vndkdep; vndkdep != nil {
 		return vndkdep.isVndkSp()
@@ -507,6 +515,10 @@ func (ctx *moduleContextImpl) isVndk() bool {
 	return ctx.mod.isVndk()
 }
 
+func (ctx *moduleContextImpl) isPgoCompile() bool {
+	return ctx.mod.isPgoCompile()
+}
+
 func (ctx *moduleContextImpl) isVndkSp() bool {
 	return ctx.mod.isVndkSp()
 }
diff --git a/cc/lto.go b/cc/lto.go
index 4757fc7e8..2ced12418 100644
--- a/cc/lto.go
+++ b/cc/lto.go
@@ -87,6 +87,13 @@ func (lto *lto) flags(ctx BaseModuleContext, flags Flags) Flags {
 			flags.LdFlags = append(flags.LdFlags, "-Wl,-plugin-opt,-emulated-tls")
 		}
 		flags.ArGoldPlugin = true
+
+		// If the module does not have a profile, be conservative and do not inline
+		// or unroll loops during LTO, in order to prevent significant size bloat.
+		if !ctx.isPgoCompile() {
+			flags.LdFlags = append(flags.LdFlags, "-Wl,-plugin-opt,-inline-threshold=0")
+			flags.LdFlags = append(flags.LdFlags, "-Wl,-plugin-opt,-unroll-threshold=0")
+		}
 	}
 	return flags
 }
diff --git a/cc/pgo.go b/cc/pgo.go
index 1e7033979..779ef39de 100644
--- a/cc/pgo.go
+++ b/cc/pgo.go
@@ -45,7 +45,7 @@ func getPgoProfileProjects(config android.DeviceConfig) []string {
 	})
 }
 
-func recordMissingProfileFile(ctx ModuleContext, missing string) {
+func recordMissingProfileFile(ctx BaseModuleContext, missing string) {
 	getNamedMapForConfig(ctx.Config(), modulesMissingProfileFile).Store(missing, true)
 }
 
@@ -63,6 +63,7 @@ type PgoProperties struct {
 
 	PgoPresent          bool `blueprint:"mutated"`
 	ShouldProfileModule bool `blueprint:"mutated"`
+	PgoCompile          bool `blueprint:"mutated"`
 }
 
 type pgo struct {
@@ -98,7 +99,7 @@ func (props *PgoProperties) addProfileGatherFlags(ctx ModuleContext, flags Flags
 	return flags
 }
 
-func (props *PgoProperties) getPgoProfileFile(ctx ModuleContext) android.OptionalPath {
+func (props *PgoProperties) getPgoProfileFile(ctx BaseModuleContext) android.OptionalPath {
 	// Test if the profile_file is present in any of the PGO profile projects
 	for _, profileProject := range getPgoProfileProjects(ctx.DeviceConfig()) {
 		path := android.ExistentPathForSource(ctx, "", profileProject, *props.Pgo.Profile_file)
@@ -232,6 +233,12 @@ func (pgo *pgo) begin(ctx BaseModuleContext) {
 			}
 		}
 	}
+
+	if !ctx.Config().IsEnvTrue("ANDROID_PGO_NO_PROFILE_USE") {
+		if profileFile := pgo.Properties.getPgoProfileFile(ctx); profileFile.Valid() {
+			pgo.Properties.PgoCompile = true
+		}
+	}
 }
 
 func (pgo *pgo) deps(ctx BaseModuleContext, deps Deps) Deps {