Use ArtMethod* .bss entries for HInvokeStaticOrDirect.

Test: m test-art-host-gtest
Test: testrunner.py --host
Test: testrunner.py --target
Test: Nexus 6P boots.
Test: Build aosp_mips64-userdebug.
Bug: 30627598
Change-Id: I0e54fdd2e91e983d475b7a04d40815ba89ae3d4f
diff --git a/compiler/linker/method_bss_mapping_encoder.h b/compiler/linker/method_bss_mapping_encoder.h
new file mode 100644
index 0000000..b2922ec
--- /dev/null
+++ b/compiler/linker/method_bss_mapping_encoder.h
@@ -0,0 +1,79 @@
+/*
+ * Copyright (C) 2017 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_METHOD_BSS_MAPPING_ENCODER_H_
+#define ART_COMPILER_LINKER_METHOD_BSS_MAPPING_ENCODER_H_
+
+#include "base/enums.h"
+#include "base/logging.h"
+#include "dex_file.h"
+#include "method_bss_mapping.h"
+
+namespace art {
+namespace linker {
+
+// Helper class for encoding compressed MethodBssMapping.
+class MethodBssMappingEncoder {
+ public:
+  explicit MethodBssMappingEncoder(PointerSize pointer_size)
+      : pointer_size_(static_cast<size_t>(pointer_size)) {
+    entry_.method_index = DexFile::kDexNoIndex16;
+    entry_.index_mask = 0u;
+    entry_.bss_offset = static_cast<uint32_t>(-1);
+  }
+
+  // Try to merge the next method_index -> bss_offset mapping into the current entry.
+  // Return true on success, false on failure.
+  bool TryMerge(uint32_t method_index, uint32_t bss_offset) {
+    DCHECK_NE(method_index, entry_.method_index);
+    if (entry_.bss_offset + pointer_size_ != bss_offset) {
+      return false;
+    }
+    uint32_t diff = method_index - entry_.method_index;
+    if (diff > 16u) {
+      return false;
+    }
+    if ((entry_.index_mask & ~(static_cast<uint32_t>(-1) << diff)) != 0u) {
+      return false;
+    }
+    entry_.method_index = method_index;
+    // Insert the bit indicating the method index we've just overwritten
+    // and shift bits indicating method indexes before that.
+    entry_.index_mask = dchecked_integral_cast<uint16_t>(
+        (static_cast<uint32_t>(entry_.index_mask) | 0x10000u) >> diff);
+    entry_.bss_offset = bss_offset;
+    return true;
+  }
+
+  void Reset(uint32_t method_index, uint32_t bss_offset) {
+    entry_.method_index = method_index;
+    entry_.index_mask = 0u;
+    entry_.bss_offset = bss_offset;
+  }
+
+  MethodBssMappingEntry GetEntry() {
+    return entry_;
+  }
+
+ private:
+  size_t pointer_size_;
+  MethodBssMappingEntry entry_;
+};
+
+}  // namespace linker
+}  // namespace art
+
+#endif  // ART_COMPILER_LINKER_METHOD_BSS_MAPPING_ENCODER_H_