Refactor RelativePatcher out of OatWriter.

Move the relative patcher classes to compiler/linker/ and
compiler/linker/<arch>/ . Refactor them to avoid OatWriter
dependency so that they can be unit tested. Add tests for
x86 and x86-64.

Change-Id: I1b42baa9fc431378e4cce1399bec590c5b5a409f
diff --git a/compiler/linker/x86/relative_patcher_x86_base.h b/compiler/linker/x86/relative_patcher_x86_base.h
new file mode 100644
index 0000000..9e1fc0c
--- /dev/null
+++ b/compiler/linker/x86/relative_patcher_x86_base.h
@@ -0,0 +1,48 @@
+/*
+ * Copyright (C) 2015 The Android Open Source Project
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+#ifndef ART_COMPILER_LINKER_X86_RELATIVE_PATCHER_X86_BASE_H_
+#define ART_COMPILER_LINKER_X86_RELATIVE_PATCHER_X86_BASE_H_
+
+#include "linker/relative_patcher.h"
+
+namespace art {
+namespace linker {
+
+class X86BaseRelativePatcher : public RelativePatcher {
+ public:
+  uint32_t ReserveSpace(uint32_t offset,
+                        const CompiledMethod* compiled_method ATTRIBUTE_UNUSED) OVERRIDE;
+  uint32_t WriteThunks(OutputStream* out ATTRIBUTE_UNUSED, uint32_t offset) OVERRIDE;
+  void PatchCall(std::vector<uint8_t>* code, uint32_t literal_offset,
+                 uint32_t patch_offset, uint32_t target_offset) OVERRIDE;
+
+ protected:
+  X86BaseRelativePatcher() { }
+
+  // PC displacement from patch location; the base address of x86/x86-64 relative
+  // calls and x86-64 RIP-relative addressing is the PC of the next instruction and
+  // the patch location is 4 bytes earlier.
+  static constexpr int32_t kPcDisplacement = 4;
+
+ private:
+  DISALLOW_COPY_AND_ASSIGN(X86BaseRelativePatcher);
+};
+
+}  // namespace linker
+}  // namespace art
+
+#endif  // ART_COMPILER_LINKER_X86_RELATIVE_PATCHER_X86_BASE_H_