Enable ThinLTO for hwui

ThinLTO will benefit hwui on both performance and code size.

Now that hwui is with PGO, ThinLTO provides 3.8% performance improvement
on top of it (tested using hwui benchmarks on marlin device).

Enabling ThinLTO also decreases current code size of libhwui.so by 3.2%.

To be mentioned, Thinlto property in bp file will go through all static
libraries that hwui depends on (such as libskia) and enable Thinlto for
them when building hwui.

Test: Build and run benchmarks with ThinLTO enabled.
Bug: http://b/62839002
Change-Id: I89466d50c3715f6e7b0518ff10240bf8a5e9714c

1 files changed, 13 insertions, 0 deletions

diff --git a/libs/hwui/Android.bp b/libs/hwui/Android.bp
index 24d819e93ff2..35790b6558c7 100644
--- a/libs/hwui/Android.bp
+++ b/libs/hwui/Android.bp
@@ -6,6 +6,7 @@ cc_defaults {
         //"hwui_bugreport_font_cache_usage",
         //"hwui_compile_for_perf",
         "hwui_pgo",
+        "hwui_lto",
     ],
 
     cpp_std: "c++17",
@@ -126,6 +127,18 @@ cc_defaults {
     },
 }
 
+// Build hwui library with ThinLTO by default.
+cc_defaults {
+    name: "hwui_lto",
+    target: {
+        android: {
+            lto: {
+                thin: true,
+            },
+        },
+    },
+}
+
 // ------------------------
 // library
 // ------------------------