X86: Assembler support for near labels
The optimizing compiler uses 32 bit relative jumps for all forward
jumps, just in case the offset is too large to fit in one byte. Some of
the generated code knows that the jumps will in fact fit.
Add a 'NearLabel' class to the x86 and x86_64 assemblers. This will be
used to generate known short forward branches.
Add jecxz/jrcxz instructions, which only handle a short offset. They
will be used for intrinsics.
Add tests for the new instructions and NearLabel.
Change-Id: I11177f36394d35d63b32364b0e6289ee6d97de46
Signed-off-by: Mark Mendell <mark.p.mendell@intel.com>
diff --git a/compiler/utils/x86_64/assembler_x86_64.h b/compiler/utils/x86_64/assembler_x86_64.h
index da42213..c38aba5 100644
--- a/compiler/utils/x86_64/assembler_x86_64.h
+++ b/compiler/utils/x86_64/assembler_x86_64.h
@@ -302,6 +302,30 @@
};
+// This is equivalent to the Label class, used in a slightly different context. We
+// inherit the functionality of the Label class, but prevent unintended
+// derived-to-base conversions by making the base class private.
+class NearLabel : private Label {
+ public:
+ NearLabel() : Label() {}
+
+ // Expose the Label routines that we need.
+ using Label::Position;
+ using Label::LinkPosition;
+ using Label::IsBound;
+ using Label::IsUnused;
+ using Label::IsLinked;
+
+ private:
+ using Label::BindTo;
+ using Label::LinkTo;
+
+ friend class x86_64::X86_64Assembler;
+
+ DISALLOW_COPY_AND_ASSIGN(NearLabel);
+};
+
+
class X86_64Assembler FINAL : public Assembler {
public:
X86_64Assembler() {}
@@ -588,10 +612,13 @@
void hlt();
void j(Condition condition, Label* label);
+ void j(Condition condition, NearLabel* label);
+ void jrcxz(NearLabel* label);
void jmp(CpuRegister reg);
void jmp(const Address& address);
void jmp(Label* label);
+ void jmp(NearLabel* label);
X86_64Assembler* lock();
void cmpxchgl(const Address& address, CpuRegister reg);
@@ -639,6 +666,7 @@
int PreferredLoopAlignment() { return 16; }
void Align(int alignment, int offset);
void Bind(Label* label);
+ void Bind(NearLabel* label);
//
// Overridden common assembler high-level functionality
@@ -809,6 +837,7 @@
void EmitComplex(uint8_t rm, const Operand& operand, const Immediate& immediate);
void EmitLabel(Label* label, int instruction_size);
void EmitLabelLink(Label* label);
+ void EmitLabelLink(NearLabel* label);
void EmitGenericShift(bool wide, int rm, CpuRegister reg, const Immediate& imm);
void EmitGenericShift(bool wide, int rm, CpuRegister operand, CpuRegister shifter);