Optimize branch instructions in interpreter.
This CL cleans up branch instructions handling by optimizing instruction
displacement with an offset by changing the way we compute the next
instruction. On ARM, it saves at least 3 instructions for GOTO and 4
instructions for IF-XX/Z.
This CL also transforms the Instruction::At CHECK into a DCHECK. This improves
the compiled code when computing next instruction.
Change-Id: I901699201012d2dbbaef4d9158cc97b63bfbbe84
diff --git a/src/dex_instruction.h b/src/dex_instruction.h
index ae469d0..adaada7 100644
--- a/src/dex_instruction.h
+++ b/src/dex_instruction.h
@@ -162,39 +162,45 @@
}
}
+ // Reads an instruction out of the stream at the specified address.
+ static const Instruction* At(const uint16_t* code) {
+ DCHECK(code != NULL);
+ return reinterpret_cast<const Instruction*>(code);
+ }
+
+ // Reads an instruction out of the stream from the current address plus an offset.
+ const Instruction* RelativeAt(int32_t offset) const {
+ return At(reinterpret_cast<const uint16_t*>(this) + offset);
+ }
+
// Returns a pointer to the next instruction in the stream.
const Instruction* Next() const {
- size_t current_size_in_bytes = SizeInCodeUnits() * sizeof(uint16_t);
- const uint8_t* ptr = reinterpret_cast<const uint8_t*>(this);
- return reinterpret_cast<const Instruction*>(ptr + current_size_in_bytes);
+ return RelativeAt(SizeInCodeUnits());
}
// Returns a pointer to the instruction after this 1xx instruction in the stream.
const Instruction* Next_1xx() const {
DCHECK(FormatOf(Opcode()) >= k10x && FormatOf(Opcode()) <= k10t);
- size_t current_size_in_bytes = 1 * sizeof(uint16_t);
- const uint8_t* ptr = reinterpret_cast<const uint8_t*>(this);
- return reinterpret_cast<const Instruction*>(ptr + current_size_in_bytes);
+ return RelativeAt(1);
}
// Returns a pointer to the instruction after this 2xx instruction in the stream.
const Instruction* Next_2xx() const {
DCHECK(FormatOf(Opcode()) >= k20t && FormatOf(Opcode()) <= k22c);
- size_t current_size_in_bytes = 2 * sizeof(uint16_t);
- const uint8_t* ptr = reinterpret_cast<const uint8_t*>(this);
- return reinterpret_cast<const Instruction*>(ptr + current_size_in_bytes);
+ return RelativeAt(2);
}
// Returns a pointer to the instruction after this 3xx instruction in the stream.
const Instruction* Next_3xx() const {
DCHECK(FormatOf(Opcode()) >= k32x && FormatOf(Opcode()) <= k3rc);
- size_t current_size_in_bytes = 3 * sizeof(uint16_t);
- const uint8_t* ptr = reinterpret_cast<const uint8_t*>(this);
- return reinterpret_cast<const Instruction*>(ptr + current_size_in_bytes);
+ return RelativeAt(3);
}
// Returns a pointer to the instruction after this 51l instruction in the stream.
- const Instruction* Next_51l() const;
+ const Instruction* Next_51l() const {
+ DCHECK(FormatOf(Opcode()) == k51l);
+ return RelativeAt(5);
+ }
// Returns the name of this instruction's opcode.
const char* Name() const {
@@ -272,12 +278,6 @@
return static_cast<Code>(opcode);
}
- // Reads an instruction out of the stream at the specified address.
- static const Instruction* At(const uint16_t* code) {
- CHECK(code != NULL);
- return reinterpret_cast<const Instruction*>(code);
- }
-
// Returns the format of the given opcode.
static Format FormatOf(Code opcode) {
return kInstructionFormats[opcode];