ARM64: Instruction simplification for array accesses.

HArrayGet and HArraySet with variable indexes generate two
instructions on arm64, like

    add temp, obj, #data_offset
    ldr out, [temp, index LSL #shift_amount]

When we have multiple accesses to the same array, the initial `add`
instruction is redundant.

This patch introduces the first instruction simplification in the
arm64-specific instruction simplification pass. It splits HArrayGet
and HArraySet using the new arm64-specific IR HIntermediateAddress.
After that we run GVN again to squash the multiple occurrences of
HIntermediateAddress.

Change-Id: I2e3d12fbb07fed07b2cb2f3f47f99f5a032f8312

1 files changed, 8 insertions, 0 deletions

diff --git a/compiler/optimizing/instruction_simplifier_arm64.h b/compiler/optimizing/instruction_simplifier_arm64.h
index d7f4eaee80..4b697dba0e 100644
--- a/compiler/optimizing/instruction_simplifier_arm64.h
+++ b/compiler/optimizing/instruction_simplifier_arm64.h
@@ -35,6 +35,14 @@ class InstructionSimplifierArm64Visitor : public HGraphVisitor {
     }
   }
 
+  void TryExtractArrayAccessAddress(HInstruction* access,
+                                    HInstruction* array,
+                                    HInstruction* index,
+                                    int access_size);
+
+  void VisitArrayGet(HArrayGet* instruction) OVERRIDE;
+  void VisitArraySet(HArraySet* instruction) OVERRIDE;
+
   OptimizingCompilerStats* stats_;
 };