type conversion elimination for constant input

type conversion on constant input can be eliminated if the constant
value falls in the result type's range.

Test: run-test on host, 711-checker-type-conversion
Change-Id: I372139d681aa06fa6e760d7814c86ac949292813

2 files changed, 23 insertions, 0 deletions

diff --git a/compiler/optimizing/data_type.h b/compiler/optimizing/data_type.h
index 75a7fbe6ca..d253036479 100644
--- a/compiler/optimizing/data_type.h
+++ b/compiler/optimizing/data_type.h
@@ -186,6 +186,7 @@ class DataType {
   }
 
   static bool IsTypeConversionImplicit(Type input_type, Type result_type);
+  static bool IsTypeConversionImplicit(int64_t value, Type result_type);
 
   static const char* PrettyDescriptor(Type type);
 
@@ -213,6 +214,18 @@ inline bool DataType::IsTypeConversionImplicit(Type input_type, Type result_type
           MaxValueOfIntegralType(input_type) <= MaxValueOfIntegralType(result_type));
 }
 
+inline bool DataType::IsTypeConversionImplicit(int64_t value, Type result_type) {
+  if (IsIntegralType(result_type) && result_type != Type::kInt64) {
+    // If the constant value falls in the range of the result_type, type
+    // conversion isn't needed.
+    return value >= MinValueOfIntegralType(result_type) &&
+           value <= MaxValueOfIntegralType(result_type);
+  }
+  // Conversion isn't implicit if it's into non-integer types, or 64-bit int
+  // which may have different number of registers.
+  return false;
+}
+
 }  // namespace art
 
 #endif  // ART_COMPILER_OPTIMIZING_DATA_TYPE_H_
diff --git a/compiler/optimizing/instruction_simplifier.cc b/compiler/optimizing/instruction_simplifier.cc
index fbfee12be9..a6dfa475eb 100644
--- a/compiler/optimizing/instruction_simplifier.cc
+++ b/compiler/optimizing/instruction_simplifier.cc
@@ -1159,6 +1159,16 @@ void InstructionSimplifierVisitor::VisitTypeConversion(HTypeConversion* instruct
       RecordSimplification();
       return;
     }
+  } else if (input->IsIntConstant()) {
+    // Try to eliminate type conversion on int constant whose value falls into
+    // the range of the result type.
+    int32_t value = input->AsIntConstant()->GetValue();
+    if (DataType::IsTypeConversionImplicit(value, result_type)) {
+      instruction->ReplaceWith(input);
+      instruction->GetBlock()->RemoveInstruction(instruction);
+      RecordSimplification();
+      return;
+    }
   }
 }