Enable Load Store Elimination for ARM and ARM64

This patch refactors the implementation of the LoadStoreElimination
optimisation pass. Please note that this pass was disabled and not
functional for any of the backends.

The current implementation tracks aliases and handles DalvikRegs as well
as Heap memory regions. It has been tested and it is known to optimise
out the following:
  * Load - Load
  * Store - Load
  * Store - Store
  * Load Literals

Change-Id: Iefae9b696f87f833ef35c451ed4d49c5a1b6fde0

1 files changed, 3 insertions, 3 deletions

diff --git a/compiler/dex/frontend.cc b/compiler/dex/frontend.cc
index 51446f6356..bff7dff513 100644
--- a/compiler/dex/frontend.cc
+++ b/compiler/dex/frontend.cc
@@ -42,7 +42,7 @@ extern "C" void ArtUnInitQuickCompilerContext(art::CompilerDriver* driver) {
 
 /* Default optimizer/debug setting for the compiler. */
 static uint32_t kCompilerOptimizerDisableFlags = 0 |  // Disable specific optimizations
-  (1 << kLoadStoreElimination) |  // TODO: this pass has been broken for awhile - fix or delete.
+  // (1 << kLoadStoreElimination) |
   // (1 << kLoadHoisting) |
   // (1 << kSuppressLoads) |
   // (1 << kNullCheckElimination) |
@@ -96,12 +96,12 @@ static constexpr uint32_t kDisabledOptimizationsPerISA[] = {
     ~0U,
     // 1 = kArm, unused (will use kThumb2).
     ~0U,
-    // 2 = kArm64.     TODO(Arm64): enable optimizations once backend is mature enough.
-    (1 << kLoadStoreElimination) |
+    // 2 = kArm64.
     0,
     // 3 = kThumb2.
     0,
     // 4 = kX86.
+    (1 << kLoadStoreElimination) |
     0,
     // 5 = kX86_64.
     (1 << kLoadStoreElimination) |