Create helper class for DWARF expressions.
This ensures we generate valid DWARF opcodes and
it slightly simplifies the debug info writer.
Change-Id: I2ef8a9222c9a129c58f500741acd209b67e2ecff
diff --git a/compiler/dwarf/expression.h b/compiler/dwarf/expression.h
new file mode 100644
index 0000000..1503d03
--- /dev/null
+++ b/compiler/dwarf/expression.h
@@ -0,0 +1,121 @@
+/*
+ * Copyright (C) 2016 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_DWARF_EXPRESSION_H_
+#define ART_COMPILER_DWARF_EXPRESSION_H_
+
+#include <cstddef>
+#include <cstdint>
+
+#include "dwarf/dwarf_constants.h"
+#include "dwarf/writer.h"
+
+namespace art {
+namespace dwarf {
+
+// Writer for DWARF expressions which are used in .debug_info and .debug_loc sections.
+// See the DWARF specification for the precise meaning of the opcodes.
+// If multiple equivalent encodings are possible, it will choose the most compact one.
+// The writer is not exhaustive - it only implements opcodes we have needed so far.
+class Expression : private Writer<> {
+ public:
+ using Writer<>::data;
+ using Writer<>::size;
+
+ // Push signed integer on the stack.
+ void WriteOpConsts(int32_t value) {
+ if (0 <= value && value < 32) {
+ PushUint8(DW_OP_lit0 + value);
+ } else {
+ PushUint8(DW_OP_consts);
+ PushSleb128(value);
+ }
+ }
+
+ // Push unsigned integer on the stack.
+ void WriteOpConstu(uint32_t value) {
+ if (value < 32) {
+ PushUint8(DW_OP_lit0 + value);
+ } else {
+ PushUint8(DW_OP_constu);
+ PushUleb128(value);
+ }
+ }
+
+ // Variable is stored in given register.
+ void WriteOpReg(uint32_t dwarf_reg_num) {
+ if (dwarf_reg_num < 32) {
+ PushUint8(DW_OP_reg0 + dwarf_reg_num);
+ } else {
+ PushUint8(DW_OP_regx);
+ PushUleb128(dwarf_reg_num);
+ }
+ }
+
+ // Variable is stored on stack. Also see DW_AT_frame_base.
+ void WriteOpFbreg(int32_t stack_offset) {
+ PushUint8(DW_OP_fbreg);
+ PushSleb128(stack_offset);
+ }
+
+ // The variable is stored in multiple locations (pieces).
+ void WriteOpPiece(uint32_t num_bytes) {
+ PushUint8(DW_OP_piece);
+ PushUleb128(num_bytes);
+ }
+
+ // Loads 32-bit or 64-bit value depending on architecture.
+ void WriteOpDeref() { PushUint8(DW_OP_deref); }
+
+ // Loads value of given byte size.
+ void WriteOpDerefSize(uint8_t num_bytes) {
+ PushUint8(DW_OP_deref_size);
+ PushUint8(num_bytes);
+ }
+
+ // Pop two values and push their sum.
+ void WriteOpPlus() { PushUint8(DW_OP_plus); }
+
+ // Add constant value to value on top of stack.
+ void WriteOpPlusUconst(uint32_t offset) {
+ PushUint8(DW_OP_plus_uconst);
+ PushUleb128(offset);
+ }
+
+ // Negate top of stack.
+ void WriteOpNeg() { PushUint8(DW_OP_neg); }
+
+ // Pop two values and push their bitwise-AND.
+ void WriteOpAnd() { PushUint8(DW_OP_and); }
+
+ // Push stack base pointer as determined from .debug_frame.
+ void WriteOpCallFrameCfa() { PushUint8(DW_OP_call_frame_cfa); }
+
+ // Push address of the variable we are working with.
+ void WriteOpPushObjectAddress() { PushUint8(DW_OP_push_object_address); }
+
+ // Return the top stack as the value of the variable.
+ // Otherwise, the top of stack is the variable's location.
+ void WriteOpStackValue() { PushUint8(DW_OP_stack_value); }
+
+ explicit Expression(std::vector<uint8_t>* buffer) : Writer<>(buffer) {
+ buffer->clear();
+ }
+};
+} // namespace dwarf
+} // namespace art
+
+#endif // ART_COMPILER_DWARF_EXPRESSION_H_