2 files changed, 18 insertions, 1 deletions
diff --git a/compiler/optimizing/data_type.h b/compiler/optimizing/data_type.h
index 4a6c91459f..be26e67af3 100644
--- a/compiler/optimizing/data_type.h
+++ b/compiler/optimizing/data_type.h
@@ -210,6 +210,12 @@ class DataType {
   static bool IsTypeConversionImplicit(Type input_type, Type result_type);
   static bool IsTypeConversionImplicit(int64_t value, Type result_type);
 
+  static bool IsZeroExtension(Type input_type, Type result_type) {
+    return IsIntOrLongType(result_type) &&
+        IsUnsignedType(input_type) &&
+        Size(result_type) > Size(input_type);
+  }
+
   static const char* PrettyDescriptor(Type type);
 
  private:
diff --git a/compiler/optimizing/instruction_simplifier.cc b/compiler/optimizing/instruction_simplifier.cc
index 676fe6bcb7..da3703726d 100644
--- a/compiler/optimizing/instruction_simplifier.cc
+++ b/compiler/optimizing/instruction_simplifier.cc
@@ -67,7 +67,6 @@ class InstructionSimplifierVisitor : public HGraphDelegateVisitor {
   bool TryCombineVecMultiplyAccumulate(HVecMul* mul);
 
   void VisitShift(HBinaryOperation* shift);
-
   void VisitEqual(HEqual* equal) OVERRIDE;
   void VisitNotEqual(HNotEqual* equal) OVERRIDE;
   void VisitBooleanNot(HBooleanNot* bool_not) OVERRIDE;
@@ -78,6 +77,7 @@ class InstructionSimplifierVisitor : public HGraphDelegateVisitor {
   void VisitNullCheck(HNullCheck* instruction) OVERRIDE;
   void VisitArrayLength(HArrayLength* instruction) OVERRIDE;
   void VisitCheckCast(HCheckCast* instruction) OVERRIDE;
+  void VisitAbs(HAbs* instruction) OVERRIDE;
   void VisitAdd(HAdd* instruction) OVERRIDE;
   void VisitAnd(HAnd* instruction) OVERRIDE;
   void VisitCondition(HCondition* instruction) OVERRIDE;
@@ -1241,6 +1241,17 @@ void InstructionSimplifierVisitor::VisitTypeConversion(HTypeConversion* instruct
   }
 }
 
+void InstructionSimplifierVisitor::VisitAbs(HAbs* instruction) {
+  HInstruction* input = instruction->GetInput();
+  if (DataType::IsZeroExtension(input->GetType(), instruction->GetResultType())) {
+    // Zero extension from narrow to wide can never set sign bit in the wider
+    // operand, making the subsequent Abs redundant (e.g., abs(b & 0xff) for byte b).
+    instruction->ReplaceWith(input);
+    instruction->GetBlock()->RemoveInstruction(instruction);
+    RecordSimplification();
+  }
+}
+
 void InstructionSimplifierVisitor::VisitAdd(HAdd* instruction) {
   HConstant* input_cst = instruction->GetConstantRight();
   HInstruction* input_other = instruction->GetLeastConstantLeft();