Uses an object pool on x64

runtime/vm/assembler_x64.cc

Index: runtime/vm/assembler_x64.cc
===================================================================
--- runtime/vm/assembler_x64.cc	(revision 27208)
+++ runtime/vm/assembler_x64.cc	(working copy)
@@ -65,6 +65,37 @@
 #undef __
 
 
+Assembler::Assembler(bool use_far_branches)
+    : buffer_(),
+      object_pool_(GrowableObjectArray::Handle()),
+      prologue_offset_(-1),
+      comments_() {
+  // Far branching mode is only needed and implemented for MIPS and ARM.
+  ASSERT(!use_far_branches);
+  if (Isolate::Current() != Dart::vm_isolate()) {
+    object_pool_ = GrowableObjectArray::New(Heap::kOld);
+
+    // These objects and labels need to be accessible through every pool-pointer
+    // at the same index.
+    object_pool_.Add(Object::Handle(), Heap::kOld);
+    object_pool_.Add(Bool::True(), Heap::kOld);
+    object_pool_.Add(Bool::False(), Heap::kOld);
+
+    if (StubCode::UpdateStoreBuffer_entry() != NULL) {
+      FindExternalLabel(&StubCode::UpdateStoreBufferLabel(), kNotPatchable);
+    } else {
+      object_pool_.Add(Object::Handle(), Heap::kOld);
+    }
+
+    if (StubCode::CallToRuntime_entry() != NULL) {
+      FindExternalLabel(&StubCode::CallToRuntimeLabel(), kNotPatchable);
+    } else {
+      object_pool_.Add(Object::Handle(), Heap::kOld);
+    }
+  }
+}
+
+
 void Assembler::InitializeMemoryWithBreakpoints(uword data, int length) {
   memset(reinterpret_cast<void*>(data), Instr::kBreakPointInstruction, length);
 }
@@ -95,9 +126,18 @@
 }
 
 
+void Assembler::LoadExternalLabel(Register dst,
+                                  const ExternalLabel* label,
+                                  Patchability patchable,
+                                  Register pp) {
+  const int32_t offset =
+      Array::element_offset(FindExternalLabel(label, patchable));
+  LoadWordFromPoolOffset(dst, pp, offset - kHeapObjectTag);
+}
+
+
 void Assembler::call(const ExternalLabel* label) {
   AssemblerBuffer::EnsureCapacity ensured(&buffer_);
-  intptr_t call_start = buffer_.GetPosition();
 
   // Encode movq(TMP, Immediate(label->address())), but always as imm64.
   EmitRegisterREX(TMP, REX_W);
@@ -109,11 +149,41 @@
   EmitOperandREX(2, operand, REX_NONE);
   EmitUint8(0xFF);
   EmitOperand(2, operand);
+}
 
+
+void Assembler::CallPatchable(const ExternalLabel* label) {
+  intptr_t call_start = buffer_.GetPosition();
+  LoadExternalLabel(TMP, label, kPatchable, PP);
+  {

[Florian Schneider, 2013/09/06 09:58:15]

call(TMP)

[zra, 2013/09/06 17:53:26]

Done.

+    AssemblerBuffer::EnsureCapacity ensured(&buffer_);
+    // Encode call(TMP).
+    Operand operand(TMP);
+    EmitOperandREX(2, operand, REX_NONE);
+    EmitUint8(0xFF);
+    EmitOperand(2, operand);
+  }
   ASSERT((buffer_.GetPosition() - call_start) == kCallExternalLabelSize);
 }
 
 
+void Assembler::Call(const ExternalLabel* label, Register pp) {
+  if (Isolate::Current() == Dart::vm_isolate()) {
+    call(label);
+  } else {
+    LoadExternalLabel(TMP, label, kNotPatchable, pp);
+    {

[Florian Schneider, 2013/09/06 09:58:15]

call(TMP)

[zra, 2013/09/06 17:53:26]

Done.

+      AssemblerBuffer::EnsureCapacity ensured(&buffer_);
+      // Encode call(TMP).
+      Operand operand(TMP);
+      EmitOperandREX(2, operand, REX_NONE);
+      EmitUint8(0xFF);
+      EmitOperand(2, operand);
+    }
+  }
+}
+
+
 void Assembler::pushq(Register reg) {
   AssemblerBuffer::EnsureCapacity ensured(&buffer_);
   EmitRegisterREX(reg, REX_NONE);
@@ -1960,6 +2030,15 @@
 }
 
 
+void Assembler::J(Condition condition, const ExternalLabel* label,
+                  Register pp) {
+  Label no_jump;
+  j(static_cast<Condition>(condition ^ 1), &no_jump);  // Negate condition.
+  Jmp(label, pp);
+  Bind(&no_jump);
+}
+
+
 void Assembler::jmp(Register reg) {
   AssemblerBuffer::EnsureCapacity ensured(&buffer_);
   Operand operand(reg);
@@ -1995,7 +2074,6 @@
 
 void Assembler::jmp(const ExternalLabel* label) {
   AssemblerBuffer::EnsureCapacity ensured(&buffer_);
-  intptr_t call_start = buffer_.GetPosition();
 
   // Encode movq(TMP, Immediate(label->address())), but always as imm64.
   EmitRegisterREX(TMP, REX_W);
@@ -2007,11 +2085,37 @@
   EmitOperandREX(4, operand, REX_NONE);
   EmitUint8(0xFF);
   EmitOperand(4, operand);
+}
 
+
+void Assembler::JmpPatchable(const ExternalLabel* label, Register pp) {
+  intptr_t call_start = buffer_.GetPosition();
+  LoadExternalLabel(TMP, label, kPatchable, pp);
+  {
+    AssemblerBuffer::EnsureCapacity ensured(&buffer_);
+    // Encode jmp(TMP).

[Florian Schneider, 2013/09/06 09:58:15]

jmp(TMP)

[zra, 2013/09/06 17:53:26]

Done.

+    Operand operand(TMP);
+    EmitOperandREX(4, operand, REX_NONE);
+    EmitUint8(0xFF);
+    EmitOperand(4, operand);
+  }
   ASSERT((buffer_.GetPosition() - call_start) == kCallExternalLabelSize);
 }
 
 
+void Assembler::Jmp(const ExternalLabel* label, Register pp) {
+  LoadExternalLabel(TMP, label, kNotPatchable, pp);
+  {

[Florian Schneider, 2013/09/06 09:58:15]

jmp(TMP)

[zra, 2013/09/06 17:53:26]

Done.

+    AssemblerBuffer::EnsureCapacity ensured(&buffer_);
+    // Encode jmp(TMP).
+    Operand operand(TMP);
+    EmitOperandREX(4, operand, REX_NONE);
+    EmitUint8(0xFF);
+    EmitOperand(4, operand);
+  }
+}
+
+
 void Assembler::lock() {
   AssemblerBuffer::EnsureCapacity ensured(&buffer_);
   EmitUint8(0xF0);
@@ -2091,49 +2195,110 @@
 }
 
 
-void Assembler::LoadObject(Register dst, const Object& object) {
-  if (object.IsSmi() || object.InVMHeap()) {
+intptr_t Assembler::FindObject(const Object& obj) {
+  // The object pool cannot be used in the vm isolate.
+  ASSERT(Isolate::Current() != Dart::vm_isolate());
+  ASSERT(obj.IsNotTemporaryScopedHandle());
+  ASSERT(obj.IsOld());
+  ASSERT(!object_pool_.IsNull());
+  // TODO(zra): This can be slow. Add a hash map from obj.raw() to
+  // object pool indexes to speed lookup.
+  for (int i = 0; i < object_pool_.Length(); i++) {
+    if (object_pool_.At(i) == obj.raw()) {
+      return i;
+    }
+  }
+  object_pool_.Add(obj, Heap::kOld);
+  return object_pool_.Length() - 1;
+}
+
+
+intptr_t Assembler::FindExternalLabel(const ExternalLabel* label,
+                                    Patchability patchable) {

[srdjan, 2013/09/06 16:22:44]

fix indent

[zra, 2013/09/06 17:53:26]

Done.

+  // The object pool cannot be used in the vm isolate.
+  ASSERT(Isolate::Current() != Dart::vm_isolate());
+  ASSERT(!object_pool_.IsNull());
+  const uword address = label->address();
+  ASSERT(Utils::IsAligned(address, 4));
+  // The address is stored in the object array as a RawSmi.
+  const Smi& smi = Smi::Handle(reinterpret_cast<RawSmi*>(address));
+  if (patchable == kNotPatchable) {
+    // An external label used in a non-patchable call shouldn't also be used in
+    // patchable calls. So, we can re-use existing entries for non-patchable
+    // calls.

[Florian Schneider, 2013/09/06 09:58:15]

I find the whole approach a little brittle: Forgetting to emit a patchable call
at sites that will be patched can lead to bugs. I'd like an assertion that a
unpatchable site is never accidentally patched. Maybe mark the entries in the
constant pool as shared and assert in debug mode that shared entries are
immutable?

Or else: How about patching the index into the constant pool instead of changing
pool entries? This would be very similar to the way patching code was done
before, just instead of replacing the imm64 address, replacing an imm32 pool
index.

[zra, 2013/09/06 17:53:26]

It is equivalent to check that a patchable external label is never re-used by a
non-patchable external label. So I've added a GrowableArray<Patchability> to
Assembler, and it has the state of the object_pool_ entries. Before reusing an
entry for a non-patchable external label, I check that the entry isn't
patchable. Srdjan thinks it would be too expensive to copy the bookkeeping over
to the Code object to check at runtime.

We're trying to remove places where we write code, so I don't think we should
patch the index instead of altering the object pool entry.

+    // TODO(zra): This can be slow. Add a hash map from obj.raw() to
+    // object pool indexes to speed lookup.
+    for (int i = 0; i < object_pool_.Length(); i++) {
+      if (object_pool_.At(i) == smi.raw()) {
+        return i;
+      }
+    }

[srdjan, 2013/09/06 16:22:44]

Could you replace this code with call to Assembler::FindObject?

[zra, 2013/09/06 17:53:26]

Done.

+  }
+  // If the call is patchable, do not reuse an existing entry since each
+  // reference may be patched independently.
+  object_pool_.Add(smi, Heap::kOld);
+  return object_pool_.Length() - 1;
+}
+
+
+bool Assembler::CanLoadFromObjectPool(const Object& object) {
+  return !object.IsSmi() &&  // Not a Smi
+         // Not in the VMHeap, OR is one of the VMHeap objects we put in every
+         // object pool.
+         (!object.InVMHeap() || (object.raw() == Object::null()) ||
+                                (object.raw() == Bool::True().raw()) ||
+                                (object.raw() == Bool::False().raw())) &&
+         object.IsNotTemporaryScopedHandle() &&
+         object.IsOld();
+}
+
+
+void Assembler::LoadWordFromPoolOffset(Register dst, Register pp,
+                                       int32_t offset) {
+  // This sequence must be of fixed size. The 'true' argument to the Address
+  // constructor forces it to use a fixed size encoding.
+  movq(dst, Address(pp, offset, true));
+}
+
+
+void Assembler::LoadObjectFromPool(Register dst, const Object& object,
+                                   Register pp) {
+  if (CanLoadFromObjectPool(object)) {
+    const int32_t offset = Array::element_offset(FindObject(object));
+    LoadWordFromPoolOffset(dst, pp, offset - kHeapObjectTag);
+  } else {
     movq(dst, Immediate(reinterpret_cast<int64_t>(object.raw())));
-  } else {
-    ASSERT(object.IsNotTemporaryScopedHandle());
-    ASSERT(object.IsOld());
-    AssemblerBuffer::EnsureCapacity ensured(&buffer_);
-    EmitRegisterREX(dst, REX_W);
-    EmitUint8(0xB8 | (dst & 7));
-    buffer_.EmitObject(object);
   }
 }
 
 
 void Assembler::StoreObject(const Address& dst, const Object& object) {
-  if (object.IsSmi() || object.InVMHeap()) {
-    movq(dst, Immediate(reinterpret_cast<int64_t>(object.raw())));
-  } else {
-    ASSERT(object.IsNotTemporaryScopedHandle());
-    ASSERT(object.IsOld());
+  if (CanLoadFromObjectPool(object)) {
     LoadObject(TMP, object);
     movq(dst, TMP);
+  } else {
+    movq(dst, Immediate(reinterpret_cast<int64_t>(object.raw())));
   }
 }
 
 
 void Assembler::PushObject(const Object& object) {
-  if (object.IsSmi() || object.InVMHeap()) {
-    pushq(Immediate(reinterpret_cast<int64_t>(object.raw())));
-  } else {
+  if (CanLoadFromObjectPool(object)) {
     LoadObject(TMP, object);
     pushq(TMP);
+  } else {
+    pushq(Immediate(reinterpret_cast<int64_t>(object.raw())));
   }
 }
 
 
 void Assembler::CompareObject(Register reg, const Object& object) {
-  if (object.IsSmi() || object.InVMHeap()) {
-    cmpq(reg, Immediate(reinterpret_cast<int64_t>(object.raw())));
-  } else {
+  if (CanLoadFromObjectPool(object)) {
     ASSERT(reg != TMP);
     LoadObject(TMP, object);
     cmpq(reg, TMP);
+  } else {
+    cmpq(reg, Immediate(reinterpret_cast<int64_t>(object.raw())));
   }
 }
 
@@ -2196,7 +2361,7 @@
   if (object != RAX) {
     movq(RAX, object);
   }
-  call(&StubCode::UpdateStoreBufferLabel());
+  Call(&StubCode::UpdateStoreBufferLabel(), PP);
   if (value != RAX) popq(RAX);
   Bind(&done);
 }
@@ -2298,6 +2463,23 @@
 }
 
 
+void Assembler::LeaveFrameWithPP() {
+  movq(PP, Address(RBP, -2 * kWordSize));
+  LeaveFrame();
+}
+
+
+void Assembler::ReturnPatchable() {
+  // This sequence must have a fixed size so that it can be patched by the
+  // debugger.
+  intptr_t start = buffer_.GetPosition();
+  LeaveFrameWithPP();
+  ret();
+  nop(4);
+  ASSERT((buffer_.GetPosition() - start) == 13);
+}
+
+
 void Assembler::ReserveAlignedFrameSpace(intptr_t frame_space) {
   // Reserve space for arguments and align frame before entering
   // the C++ world.
@@ -2378,41 +2560,96 @@
 }
 
 
+void Assembler::LoadPoolPointer(Register pp) {
+  Label next;
+  call(&next);
+  Bind(&next);
+
+  // Load new pool pointer.
+  const intptr_t object_pool_pc_dist =
+      Instructions::HeaderSize() - Instructions::object_pool_offset() +
+      CodeSize();
+  popq(pp);
+  movq(pp, Address(pp, -object_pool_pc_dist));
+}
+
+
 void Assembler::EnterDartFrame(intptr_t frame_size) {
   EnterFrame(0);
+
   Label dart_entry;
   call(&dart_entry);
   Bind(&dart_entry);
   // The runtime system assumes that the code marker address is
   // kEntryPointToPcMarkerOffset bytes from the entry.  If there is any code
   // generated before entering the frame, the address needs to be adjusted.
+  const intptr_t object_pool_pc_dist =
+      Instructions::HeaderSize() - Instructions::object_pool_offset() +
+      CodeSize();
   const intptr_t offset = kEntryPointToPcMarkerOffset - CodeSize();
   if (offset != 0) {
     addq(Address(RSP, 0), Immediate(offset));
   }
+  // Save caller's pool pointer
+  pushq(PP);
+
+  // Load callee's pool pointer.
+  movq(PP, Address(RSP, 1 * kWordSize));
+  movq(PP, Address(PP, -object_pool_pc_dist - offset));
+
   if (frame_size != 0) {
     subq(RSP, Immediate(frame_size));
   }
 }
 
 
+void Assembler::EnterDartFrameWithInfo(intptr_t frame_size,
+                                       Register new_pp, Register new_pc) {
+  if (new_pc == kNoRegister) {
+    EnterDartFrame(0);
+  } else {
+    EnterFrame(0);
+    pushq(new_pc);
+    pushq(PP);
+    movq(PP, new_pp);
+  }
+  if (frame_size != 0) {
+    subq(RSP, Immediate(frame_size));
+  }
+}
+
+
 // On entry to a function compiled for OSR, the caller's frame pointer, the
 // stack locals, and any copied parameters are already in place.  The frame
 // pointer is already set up.  The PC marker is not correct for the
 // optimized function and there may be extra space for spill slots to
 // allocate.
-void Assembler::EnterOsrFrame(intptr_t extra_size) {
-  Label dart_entry;
-  call(&dart_entry);
-  Bind(&dart_entry);
-  // The runtime system assumes that the code marker address is
-  // kEntryPointToPcMarkerOffset bytes from the entry.  Since there is no
-  // code to set up the frame pointer, the address needs to be adjusted.
-  const intptr_t offset = kEntryPointToPcMarkerOffset - CodeSize();
-  if (offset != 0) {
-    addq(Address(RSP, 0), Immediate(offset));
+void Assembler::EnterOsrFrame(intptr_t extra_size,
+                              Register new_pp, Register new_pc) {
+  if (new_pc == kNoRegister) {
+    Label dart_entry;
+    call(&dart_entry);
+    Bind(&dart_entry);
+    // The runtime system assumes that the code marker address is
+    // kEntryPointToPcMarkerOffset bytes from the entry.  Since there is no
+    // code to set up the frame pointer, the address needs to be adjusted.
+    const intptr_t object_pool_pc_dist =
+        Instructions::HeaderSize() - Instructions::object_pool_offset() +
+        CodeSize();
+    const intptr_t offset = kEntryPointToPcMarkerOffset - CodeSize();
+    if (offset != 0) {
+      addq(Address(RSP, 0), Immediate(offset));
+    }
+
+    // Load callee's pool pointer.
+    movq(PP, Address(RSP, 0));
+    movq(PP, Address(PP, -object_pool_pc_dist - offset));
+
+    popq(Address(RBP, kPcMarkerSlotFromFp * kWordSize));
+  } else {
+    movq(Address(RBP, kPcMarkerSlotFromFp * kWordSize), new_pc);
+    movq(PP, new_pp);
   }
-  popq(Address(RBP, kPcMarkerSlotFromFp * kWordSize));
   if (extra_size != 0) {
     subq(RSP, Immediate(extra_size));
   }
@@ -2425,6 +2662,14 @@
 }
 
 
+void Assembler::EnterStubFrameWithPP() {
+  EnterFrame(0);
+  pushq(Immediate(0));  // Push 0 in the saved PC area for stub frames.
+  pushq(PP);  // Save caller's pool pointer
+  LoadPoolPointer(PP);
+}
+
+
 void Assembler::TryAllocate(const Class& cls,
                             Label* failure,
                             bool near_jump,
@@ -2648,6 +2893,30 @@
 }
 
 
+void Assembler::FixedSizeAddressOffsetTest() {
+  movq(RAX, Address(RSP, 0, true));
+  movq(RAX, Address(RBP, 0, true));
+  movq(RAX, Address(RAX, 0, true));
+  movq(RAX, Address(R10, 0, true));
+  movq(RAX, Address(R12, 0, true));
+  movq(RAX, Address(R13, 0, true));
+  movq(R10, Address(RAX, 0, true));
+
+  movq(RAX, Address(RSP, kWordSize, true));
+  movq(RAX, Address(RBP, kWordSize, true));
+  movq(RAX, Address(RAX, kWordSize, true));
+  movq(RAX, Address(R10, kWordSize, true));
+  movq(RAX, Address(R12, kWordSize, true));
+  movq(RAX, Address(R13, kWordSize, true));
+
+  movq(RAX, Address(RSP, -kWordSize, true));
+  movq(RAX, Address(RBP, -kWordSize, true));
+  movq(RAX, Address(RAX, -kWordSize, true));
+  movq(RAX, Address(R10, -kWordSize, true));
+  movq(RAX, Address(R12, -kWordSize, true));
+  movq(RAX, Address(R13, -kWordSize, true));
+}
+
 }  // namespace dart
 
 #endif  // defined TARGET_ARCH_X64