[arm64] Align stack ops in the arm64 deoptimizer

Align the stack operations in the deoptimizer and take the opportunity to
factorise and improve the code generated for copying.

Bug: v8:6644
Change-Id: I854a975c371936bbf720d56e80dc0c9d68fe7c92
Reviewed-on: https://chromium-review.googlesource.com/763535Reviewed-by: Jaroslav Sevcik <jarin@chromium.org>
Commit-Queue: Martyn Capewell <martyn.capewell@arm.com>
Cr-Commit-Position: refs/heads/master@{#49420}

src/arm64/deoptimizer-arm64.cc

@@ -16,6 +16,77 @@ namespace internal {
 
 #define __ masm()->
 
+namespace {
+
+void CopyRegListToFrame(MacroAssembler* masm, const Register& dst,
+                        int dst_offset, const CPURegList& reg_list,
+                        const Register& temp0, const Register& temp1,
+                        int src_offset = 0) {
+  DCHECK_EQ(reg_list.Count() % 2, 0);
+  UseScratchRegisterScope temps(masm);
+  CPURegList copy_to_input = reg_list;
+  int reg_size = reg_list.RegisterSizeInBytes();
+  DCHECK_EQ(temp0.SizeInBytes(), reg_size);
+  DCHECK_EQ(temp1.SizeInBytes(), reg_size);
+
+  // Compute some temporary addresses to avoid having the macro assembler set
+  // up a temp with an offset for accesses out of the range of the addressing
+  // mode.
+  Register src = temps.AcquireX();
+  masm->Add(src, masm->StackPointer(), src_offset);
+  masm->Add(dst, dst, dst_offset);
+
+  // Write reg_list into the frame pointed to by dst.
+  for (int i = 0; i < reg_list.Count(); i += 2) {
+    masm->Ldp(temp0, temp1, MemOperand(src, i * reg_size));
+
+    CPURegister reg0 = copy_to_input.PopLowestIndex();
+    CPURegister reg1 = copy_to_input.PopLowestIndex();
+    int offset0 = reg0.code() * reg_size;
+    int offset1 = reg1.code() * reg_size;
+
+    // Pair up adjacent stores, otherwise write them separately.
+    if (offset1 == offset0 + reg_size) {
+      masm->Stp(temp0, temp1, MemOperand(dst, offset0));
+    } else {
+      masm->Str(temp0, MemOperand(dst, offset0));
+      masm->Str(temp1, MemOperand(dst, offset1));
+    }
+  }
+  masm->Sub(dst, dst, dst_offset);
+}
+
+void RestoreRegList(MacroAssembler* masm, const CPURegList& reg_list,
+                    const Register& src_base, int src_offset) {
+  DCHECK_EQ(reg_list.Count() % 2, 0);
+  UseScratchRegisterScope temps(masm);
+  CPURegList restore_list = reg_list;
+  int reg_size = restore_list.RegisterSizeInBytes();
+
+  // Compute a temporary addresses to avoid having the macro assembler set
+  // up a temp with an offset for accesses out of the range of the addressing
+  // mode.
+  Register src = temps.AcquireX();
+  masm->Add(src, src_base, src_offset);
+
+  // Restore every register in restore_list from src.
+  while (!restore_list.IsEmpty()) {
+    CPURegister reg0 = restore_list.PopLowestIndex();
+    CPURegister reg1 = restore_list.PopLowestIndex();
+    int offset0 = reg0.code() * reg_size;
+    int offset1 = reg1.code() * reg_size;
+
+    // Pair up adjacent loads, otherwise read them separately.
+    if (offset1 == offset0 + reg_size) {
+      masm->Ldp(reg0, reg1, MemOperand(src, offset0));
+    } else {
+      masm->Ldr(reg0, MemOperand(src, offset0));
+      masm->Ldr(reg1, MemOperand(src, offset1));
+    }
+  }
+}
+}  // namespace
+
 void Deoptimizer::TableEntryGenerator::Generate() {
   GeneratePrologue();
 
@@ -27,17 +98,23 @@ void Deoptimizer::TableEntryGenerator::Generate() {
   CPURegList saved_double_registers(
       CPURegister::kVRegister, kDRegSizeInBits,
       RegisterConfiguration::Default()->allocatable_double_codes_mask());
+  DCHECK_EQ(saved_double_registers.Count() % 2, 0);
   __ PushCPURegList(saved_double_registers);
 
-  // Save all allocatable float registers.
   CPURegList saved_float_registers(
       CPURegister::kVRegister, kSRegSizeInBits,
       RegisterConfiguration::Default()->allocatable_float_codes_mask());
+  DCHECK_EQ(saved_float_registers.Count() % 4, 0);
   __ PushCPURegList(saved_float_registers);
 
-  // We save all the registers expcept jssp, sp and lr.
+  // We save all the registers except sp, lr and the masm scratches.
   CPURegList saved_registers(CPURegister::kRegister, kXRegSizeInBits, 0, 27);
+  saved_registers.Remove(ip0);
+  saved_registers.Remove(ip1);
+  // TODO(arm): padding here can be replaced with jssp/x28 when allocatable.
+  saved_registers.Combine(padreg);
   saved_registers.Combine(fp);
+  DCHECK_EQ(saved_registers.Count() % 2, 0);
   __ PushCPURegList(saved_registers);
 
   __ Mov(x3, Operand(ExternalReference(IsolateAddressId::kCEntryFPAddress,
@@ -63,18 +140,24 @@ void Deoptimizer::TableEntryGenerator::Generate() {
   // Get the address of the location in the code object. This is the return
   // address for lazy deoptimization.
   __ Mov(code_object, lr);
-  // Compute the fp-to-sp delta, and correct one word for bailout id.
+  // Compute the fp-to-sp delta, adding two words for alignment padding and
+  // bailout id.
   __ Add(fp_to_sp, __ StackPointer(),
-         kSavedRegistersAreaSize + (1 * kPointerSize));
+         kSavedRegistersAreaSize + (2 * kPointerSize));
   __ Sub(fp_to_sp, fp, fp_to_sp);
 
   // Allocate a new deoptimizer object.
-  __ Mov(x0, 0);
-  Label context_check;
   __ Ldr(x1, MemOperand(fp, CommonFrameConstants::kContextOrFrameTypeOffset));
-  __ JumpIfSmi(x1, &context_check);
+
+  // Ensure we can safely load from below fp.
+  DCHECK_GT(kSavedRegistersAreaSize,
+            -JavaScriptFrameConstants::kFunctionOffset);
   __ Ldr(x0, MemOperand(fp, JavaScriptFrameConstants::kFunctionOffset));
-  __ bind(&context_check);
+
+  // If x1 is a smi, zero x0.
+  __ Tst(x1, kSmiTagMask);
+  __ CzeroX(x0, eq);
+
   __ Mov(x1, type());
   // Following arguments are already loaded:
   //  - x2: bailout id
@@ -95,70 +178,47 @@ void Deoptimizer::TableEntryGenerator::Generate() {
   __ Ldr(x1, MemOperand(deoptimizer, Deoptimizer::input_offset()));
 
   // Copy core registers into the input frame.
-  CPURegList copy_to_input = saved_registers;
-  for (int i = 0; i < saved_registers.Count(); i++) {
-    __ Peek(x2, i * kPointerSize);
-    CPURegister current_reg = copy_to_input.PopLowestIndex();
-    int offset = (current_reg.code() * kPointerSize) +
-        FrameDescription::registers_offset();
-    __ Str(x2, MemOperand(x1, offset));
-  }
+  CopyRegListToFrame(masm(), x1, FrameDescription::registers_offset(),
+                     saved_registers, x2, x3);
 
   // Copy double registers to the input frame.
-  CPURegList copy_double_to_input = saved_double_registers;
-  for (int i = 0; i < saved_double_registers.Count(); i++) {
-    int src_offset = kDoubleRegistersOffset + (i * kDoubleSize);
-    __ Peek(x2, src_offset);
-    CPURegister reg = copy_double_to_input.PopLowestIndex();
-    int dst_offset = FrameDescription::double_registers_offset() +
-                     (reg.code() * kDoubleSize);
-    __ Str(x2, MemOperand(x1, dst_offset));
-  }
+  CopyRegListToFrame(masm(), x1, FrameDescription::double_registers_offset(),
+                     saved_double_registers, x2, x3, kDoubleRegistersOffset);
 
   // Copy float registers to the input frame.
-  CPURegList copy_float_to_input = saved_float_registers;
-  for (int i = 0; i < saved_float_registers.Count(); i++) {
-    int src_offset = kFloatRegistersOffset + (i * kFloatSize);
-    __ Peek(w2, src_offset);
-    CPURegister reg = copy_float_to_input.PopLowestIndex();
-    int dst_offset =
-        FrameDescription::float_registers_offset() + (reg.code() * kFloatSize);
-    __ Str(w2, MemOperand(x1, dst_offset));
-  }
+  // TODO(arm): these are the lower 32-bits of the double registers stored
+  // above, so we shouldn't need to store them again.
+  CopyRegListToFrame(masm(), x1, FrameDescription::float_registers_offset(),
+                     saved_float_registers, w2, w3, kFloatRegistersOffset);
 
-  // Remove the bailout id and the saved registers from the stack.
-  __ Drop(1 + (kSavedRegistersAreaSize / kXRegSize));
+  // Remove the padding, bailout id and the saved registers from the stack.
+  DCHECK_EQ(kSavedRegistersAreaSize % kXRegSize, 0);
+  __ Drop(2 + (kSavedRegistersAreaSize / kXRegSize));
 
   // Compute a pointer to the unwinding limit in register x2; that is
   // the first stack slot not part of the input frame.
   Register unwind_limit = x2;
   __ Ldr(unwind_limit, MemOperand(x1, FrameDescription::frame_size_offset()));
-  __ Add(unwind_limit, unwind_limit, __ StackPointer());
 
   // Unwind the stack down to - but not including - the unwinding
   // limit and copy the contents of the activation frame to the input
   // frame description.
   __ Add(x3, x1, FrameDescription::frame_content_offset());
-  Label pop_loop;
-  Label pop_loop_header;
-  __ B(&pop_loop_header);
-  __ Bind(&pop_loop);
-  __ Pop(x4);
-  __ Str(x4, MemOperand(x3, kPointerSize, PostIndex));
-  __ Bind(&pop_loop_header);
-  __ Cmp(unwind_limit, __ StackPointer());
-  __ B(ne, &pop_loop);
+  __ SlotAddress(x1, 0);
+  __ Lsr(unwind_limit, unwind_limit, kPointerSizeLog2);
+  __ Mov(x5, unwind_limit);
+  __ CopyDoubleWords(x3, x1, x5);
+  __ Drop(unwind_limit);
 
   // Compute the output frame in the deoptimizer.
-  __ Push(x0);  // Preserve deoptimizer object across call.
-
+  __ Push(padreg, x0);  // Preserve deoptimizer object across call.
   {
     // Call Deoptimizer::ComputeOutputFrames().
     AllowExternalCallThatCantCauseGC scope(masm());
     __ CallCFunction(
         ExternalReference::compute_output_frames_function(isolate()), 1);
   }
-  __ Pop(x4);  // Restore deoptimizer object (class Deoptimizer).
+  __ Pop(x4, padreg);  // Restore deoptimizer object (class Deoptimizer).
 
   __ Ldr(__ StackPointer(),
          MemOperand(x4, Deoptimizer::caller_frame_top_offset()));
@@ -173,43 +233,29 @@ void Deoptimizer::TableEntryGenerator::Generate() {
 
   __ Bind(&outer_push_loop);
   Register current_frame = x2;
-  __ Ldr(current_frame, MemOperand(x0, 0));
+  Register frame_size = x3;
+  __ Ldr(current_frame, MemOperand(x0, kPointerSize, PostIndex));
   __ Ldr(x3, MemOperand(current_frame, FrameDescription::frame_size_offset()));
-  __ B(&inner_loop_header);
+  __ Lsr(frame_size, x3, kPointerSizeLog2);
+  __ Claim(frame_size);
 
-  __ Bind(&inner_push_loop);
-  __ Sub(x3, x3, kPointerSize);
-  __ Add(x6, current_frame, x3);
-  __ Ldr(x7, MemOperand(x6, FrameDescription::frame_content_offset()));
-  __ Push(x7);
-  __ Bind(&inner_loop_header);
-  __ Cbnz(x3, &inner_push_loop);
+  __ Add(x7, current_frame, FrameDescription::frame_content_offset());
+  __ SlotAddress(x6, 0);
+  __ CopyDoubleWords(x6, x7, frame_size);
 
-  __ Add(x0, x0, kPointerSize);
   __ Bind(&outer_loop_header);
   __ Cmp(x0, x1);
   __ B(lt, &outer_push_loop);
 
   __ Ldr(x1, MemOperand(x4, Deoptimizer::input_offset()));
-  DCHECK(!saved_double_registers.IncludesAliasOf(crankshaft_fp_scratch) &&
-         !saved_double_registers.IncludesAliasOf(fp_zero) &&
-         !saved_double_registers.IncludesAliasOf(fp_scratch));
-  while (!saved_double_registers.IsEmpty()) {
-    const CPURegister reg = saved_double_registers.PopLowestIndex();
-    int src_offset = FrameDescription::double_registers_offset() +
-                     (reg.code() * kDoubleSize);
-    __ Ldr(reg, MemOperand(x1, src_offset));
-  }
+  RestoreRegList(masm(), saved_double_registers, x1,
+                 FrameDescription::double_registers_offset());
 
   // TODO(all): ARM copies a lot (if not all) of the last output frame onto the
   // stack, then pops it all into registers. Here, we try to load it directly
   // into the relevant registers. Is this correct? If so, we should improve the
   // ARM code.
 
-  // TODO(all): This code needs to be revisited, We probably don't need to
-  // restore all the registers as fullcodegen does not keep live values in
-  // registers (note that at least fp must be restored though).
-
   // Restore registers from the last output frame.
   // Note that lr is not in the list of saved_registers and will be restored
   // later. We can use it to hold the address of last output frame while
@@ -218,19 +264,10 @@ void Deoptimizer::TableEntryGenerator::Generate() {
   Register last_output_frame = lr;
   __ Mov(last_output_frame, current_frame);
 
-  // We don't need to restore x7 as it will be clobbered later to hold the
-  // continuation address.
-  Register continuation = x7;
-  saved_registers.Remove(continuation);
-
-  while (!saved_registers.IsEmpty()) {
-    // TODO(all): Look for opportunities to optimize this by using ldp.
-    CPURegister current_reg = saved_registers.PopLowestIndex();
-    int offset = (current_reg.code() * kPointerSize) +
-        FrameDescription::registers_offset();
-    __ Ldr(current_reg, MemOperand(last_output_frame, offset));
-  }
+  RestoreRegList(masm(), saved_registers, last_output_frame,
+                 FrameDescription::registers_offset());
 
+  Register continuation = x7;
   __ Ldr(continuation, MemOperand(last_output_frame,
                                   FrameDescription::continuation_offset()));
   __ Ldr(lr, MemOperand(last_output_frame, FrameDescription::pc_offset()));
@@ -268,7 +305,7 @@ void Deoptimizer::TableEntryGenerator::GeneratePrologue() {
     }
   }
   __ Bind(&done);
-  __ Push(entry_id);
+  __ Push(padreg, entry_id);
 }
 
 bool Deoptimizer::PadTopOfStackRegister() { return true; }