Fast path Region::orSelf when empty

If a Region is empty, orSelf is equivalent to just assigning from the
other Region/Rect, so we don't need to perform a whole rasterization
pass.

Test: libsurfaceflinger_unittest
Test: simpleperf measurement of SF shows workload reduction
Bug: 153112939
Change-Id: Iefa0e0177a0e85ce72e37842885d3c8b68ce6025

1 files changed, 8 insertions, 0 deletions

diff --git a/libs/ui/Region.cpp b/libs/ui/Region.cpp
index bf487c4aec..d929cc30ba 100644
--- a/libs/ui/Region.cpp
+++ b/libs/ui/Region.cpp
@@ -306,6 +306,10 @@ void Region::addRectUnchecked(int l, int t, int r, int b)
 // ----------------------------------------------------------------------------
 
 Region& Region::orSelf(const Rect& r) {
+    if (isEmpty()) {
+        set(r);
+        return *this;
+    }
     return operationSelf(r, op_or);
 }
 Region& Region::xorSelf(const Rect& r) {
@@ -326,6 +330,10 @@ Region& Region::operationSelf(const Rect& r, uint32_t op) {
 // ----------------------------------------------------------------------------
 
 Region& Region::orSelf(const Region& rhs) {
+    if (isEmpty()) {
+        *this = rhs;
+        return *this;
+    }
     return operationSelf(rhs, op_or);
 }
 Region& Region::xorSelf(const Region& rhs) {