Introduce Signature type to avoid string comparisons.

Method resolution currently creates strings to then compare with strings formed
from methods in other dex files. The temporary strings are purely created for
the sake of comparisons. This change creates a new Signature type that
represents a method signature but not as a string. This type supports
comparisons and so can be used when searching for methods in resolution.

With this change malloc is no longer the hottest method during dex2oat (now its
memset) and allocations during verification have been reduced. The verifier is
commonly what is populating the dex cache for methods and fields not declared
in the dex file itself.

Change-Id: I5ef0542823fbcae868aaa4a2457e8da7df0e9dae

1 files changed, 86 insertions, 9 deletions

diff --git a/runtime/dex_file.h b/runtime/dex_file.h
index 4534b41e92..40e4c72772 100644
--- a/runtime/dex_file.h
+++ b/runtime/dex_file.h
@@ -40,6 +40,7 @@ namespace mirror {
   class DexCache;
 }  // namespace mirror
 class ClassLinker;
+class Signature;
 class StringPiece;
 class ZipArchive;
 
@@ -559,10 +560,8 @@ class DexFile {
     return GetProtoId(method_id.proto_idx_);
   }
 
-  // Returns the signature of a method id.
-  const std::string GetMethodSignature(const MethodId& method_id) const {
-    return CreateMethodSignature(method_id.proto_idx_, NULL);
-  }
+  // Returns a representation of the signature of a method id.
+  const Signature GetMethodSignature(const MethodId& method_id) const;
 
   // Returns the name of a method id.
   const char* GetMethodName(const MethodId& method_id) const {
@@ -656,15 +655,16 @@ class DexFile {
   }
 
   // Looks up a proto id for a given return type and signature type list
-  const ProtoId* FindProtoId(uint16_t return_type_id,
+  const ProtoId* FindProtoId(uint16_t return_type_idx,
                              const std::vector<uint16_t>& signature_type_idxs_) const;
 
   // Given a signature place the type ids into the given vector, returns true on success
-  bool CreateTypeList(uint16_t* return_type_idx, std::vector<uint16_t>* param_type_idxs,
-                      const std::string& signature) const;
+  bool CreateTypeList(const StringPiece& signature, uint16_t* return_type_idx,
+                      std::vector<uint16_t>* param_type_idxs) const;
 
-  // Given a proto_idx decode the type list and return type into a method signature
-  std::string CreateMethodSignature(uint32_t proto_idx, int32_t* unicode_length) const;
+  // Create a Signature from the given string signature or return Signature::NoSignature if not
+  // possible.
+  const Signature CreateSignature(const StringPiece& signature) const;
 
   // Returns the short form method descriptor for the given prototype.
   const char* GetShorty(uint32_t proto_idx) const {
@@ -942,6 +942,83 @@ class DexFileParameterIterator {
   DISALLOW_IMPLICIT_CONSTRUCTORS(DexFileParameterIterator);
 };
 
+// Abstract the signature of a method.
+class Signature {
+ public:
+  std::string ToString() const;
+
+  static Signature NoSignature() {
+    return Signature();
+  }
+
+  bool operator==(const Signature& rhs) const {
+    if (dex_file_ == nullptr) {
+      return rhs.dex_file_ == nullptr;
+    }
+    if (rhs.dex_file_ == nullptr) {
+      return false;
+    }
+    if (dex_file_ == rhs.dex_file_) {
+      return proto_id_ == rhs.proto_id_;
+    }
+    StringPiece shorty(dex_file_->StringDataAsStringPieceByIdx(proto_id_->shorty_idx_));
+    if (shorty != rhs.dex_file_->StringDataAsStringPieceByIdx(rhs.proto_id_->shorty_idx_)) {
+      return false;  // Shorty mismatch.
+    }
+    if (shorty[0] == 'L') {
+      const DexFile::TypeId& return_type_id = dex_file_->GetTypeId(proto_id_->return_type_idx_);
+      const DexFile::TypeId& rhs_return_type_id =
+          rhs.dex_file_->GetTypeId(rhs.proto_id_->return_type_idx_);
+      if (dex_file_->StringDataAsStringPieceByIdx(return_type_id.descriptor_idx_) !=
+          rhs.dex_file_->StringDataAsStringPieceByIdx(rhs_return_type_id.descriptor_idx_)) {
+        return false;  // Return type mismatch.
+      }
+    }
+    if (shorty.find('L', 1) != StringPiece::npos) {
+      const DexFile::TypeList* params = dex_file_->GetProtoParameters(*proto_id_);
+      const DexFile::TypeList* rhs_params = rhs.dex_file_->GetProtoParameters(*rhs.proto_id_);
+      // Both lists are empty or have contents, or else shorty is broken.
+      DCHECK_EQ(params == nullptr, rhs_params == nullptr);
+      if (params != nullptr) {
+        uint32_t params_size = params->Size();
+        DCHECK_EQ(params_size, rhs_params->Size());  // Parameter list size must match.
+        for (uint32_t i = 0; i < params_size; ++i) {
+          const DexFile::TypeId& param_id = dex_file_->GetTypeId(params->GetTypeItem(i).type_idx_);
+          const DexFile::TypeId& rhs_param_id =
+              rhs.dex_file_->GetTypeId(rhs_params->GetTypeItem(i).type_idx_);
+          if (dex_file_->StringDataAsStringPieceByIdx(param_id.descriptor_idx_) !=
+              rhs.dex_file_->StringDataAsStringPieceByIdx(rhs_param_id.descriptor_idx_)) {
+            return false;  // Parameter type mismatch.
+          }
+        }
+      }
+    }
+    return true;
+  }
+
+  bool operator!=(const Signature& rhs) const {
+    return !(*this == rhs);
+  }
+
+  bool operator==(const StringPiece& rhs) const {
+    // TODO: Avoid temporary string allocation.
+    return ToString() == rhs;
+  }
+
+ private:
+  Signature(const DexFile* dex, const DexFile::ProtoId& proto) : dex_file_(dex), proto_id_(&proto) {
+  }
+
+  Signature() : dex_file_(nullptr), proto_id_(nullptr) {
+  }
+
+  friend class DexFile;
+
+  const DexFile* const dex_file_;
+  const DexFile::ProtoId* const proto_id_;
+};
+std::ostream& operator<<(std::ostream& os, const Signature& sig);
+
 // Iterate and decode class_data_item
 class ClassDataItemIterator {
  public: