Add a write barrier elimination pass

We can eliminate redundant write barriers as we don't need several
for the same receiver. For example:

```
MyObject o;
o.inner_obj = io;
o.inner_obj2 = io2;
o.inner_obj3 = io3;
```

We can keep the write barrier for `inner_obj` and remove the other
two.

Note that we cannot perform this optimization across
invokes, suspend check, or instructions that can throw.

Local improvements (pixel 5, speed compile):
 * System server: -280KB (-0.56%)
 * SystemUIGoogle: -330KB (-1.16%)
 * AGSA: -3876KB (-1.19%)

Bug: 260843353
Fixes: 260843353
Change-Id: Ibf98efbe891ee00e46125853c3e97ae30aa3ff30

1 files changed, 7 insertions, 0 deletions

diff --git a/compiler/optimizing/optimizing_compiler.cc b/compiler/optimizing/optimizing_compiler.cc
index 807c78e62a..dbf247cd64 100644
--- a/compiler/optimizing/optimizing_compiler.cc
+++ b/compiler/optimizing/optimizing_compiler.cc
@@ -51,6 +51,7 @@
 #include "linker/linker_patch.h"
 #include "nodes.h"
 #include "oat_quick_method_header.h"
+#include "optimizing/write_barrier_elimination.h"
 #include "prepare_for_register_allocation.h"
 #include "reference_type_propagation.h"
 #include "register_allocator_linear_scan.h"
@@ -899,6 +900,8 @@ CodeGenerator* OptimizingCompiler::TryCompile(ArenaAllocator* allocator,
     RunBaselineOptimizations(graph, codegen.get(), dex_compilation_unit, &pass_observer);
   } else {
     RunOptimizations(graph, codegen.get(), dex_compilation_unit, &pass_observer);
+    PassScope scope(WriteBarrierElimination::kWBEPassName, &pass_observer);
+    WriteBarrierElimination(graph, compilation_stats_.get()).Run();
   }
 
   RegisterAllocator::Strategy regalloc_strategy =
@@ -992,6 +995,10 @@ CodeGenerator* OptimizingCompiler::TryCompileIntrinsic(
                    optimizations);
 
   RunArchOptimizations(graph, codegen.get(), dex_compilation_unit, &pass_observer);
+  {
+    PassScope scope(WriteBarrierElimination::kWBEPassName, &pass_observer);
+    WriteBarrierElimination(graph, compilation_stats_.get()).Run();
+  }
 
   AllocateRegisters(graph,
                     codegen.get(),