MIPS: replace RegExpCEntryStub with DirectCEntryStub.

src/mips/regexp-macro-assembler-mips.cc

 // Copyright 2012 the V8 project authors. All rights reserved.
 // Redistribution and use in source and binary forms, with or without
 // modification, are permitted provided that the following conditions are
 // met:
 //
 //     * Redistributions of source code must retain the above copyright
 //       notice, this list of conditions and the following disclaimer.
 //     * Redistributions in binary form must reproduce the above
 //       copyright notice, this list of conditions and the following
 //       disclaimer in the documentation and/or other materials provided
@@ skipping 1045 matching lines @@
 
 
 bool RegExpMacroAssemblerMIPS::CanReadUnaligned() {
   return false;
 }
 
 
 // Private methods:
 
 void RegExpMacroAssemblerMIPS::CallCheckStackGuardState(Register scratch) {
-  static const int num_arguments = 3;
-  __ PrepareCallCFunction(num_arguments, scratch);
+  __ PrepareCallCFunction(3, scratch);
+
   __ mov(a2, frame_pointer());
   // Code* of self.
   __ li(a1, Operand(masm_->CodeObject()), CONSTANT_SIZE);
-  // a0 becomes return address pointer.
+
+  // We need to make room for the return address on the stack.
+  int stack_alignment = OS::ActivationFrameAlignment();
+  ASSERT(IsAligned(stack_alignment, kPointerSize));
+  __ Subu(sp, sp, Operand(stack_alignment));
+
+  // a0 will point to the return address, placed by DirectCEntry.
+  __ mov(a0, sp);
+
   ExternalReference stack_guard_check =
       ExternalReference::re_check_stack_guard_state(masm_->isolate());
-  CallCFunctionUsingStub(stack_guard_check, num_arguments);
+  __ li(t9, Operand(stack_guard_check));
+  DirectCEntryStub stub;
+  stub.GenerateCall(masm_, t9);
+
+  ASSERT(stack_alignment != 0);
+  // Drop the return address, stack alignment, C arguments from the stack
+  // with loading saved sp.
+  __ lw(sp, MemOperand(sp, 16 + stack_alignment + kCArgsSlotsSize));

[Paul Lind, 2013/09/19 18:07:10]

Where does the magic number 16 come from? You're calling PrepareCallCFunction()
with 3 args, but those fit within the (4) on-stack ArgsSlots. You already
account for that with kCArgsSlotsSize. The only un-accounted for thing is the
return address. That would be 4 bytes, or maybe 8 to preserve alignment.

[kilvadyb, 2013/09/19 18:37:26]

The 16 comes from the allocation done by PrepareCallCFunction (3 arguments and 1
for the original stake pointer). Previous
RegExpMacroAssemblerMIPS::CallCFunctionUsingStub used the magic 16 also. I
couldn't find a good name for that. The kCArgsSlotsSize value comes from
DirectCEntryStub::Generate's stack allocation. There is no stack release/pop in
DirectCEntryStub::Generate as that function can be called from other places
where LeaveExitFrame takes care of the sp.

+
+  __ li(code_pointer(), Operand(masm_->CodeObject()));
 }
 
 
 // Helper function for reading a value out of a stack frame.
 template <typename T>
 static T& frame_entry(Address re_frame, int frame_offset) {
   return reinterpret_cast<T&>(Memory::int32_at(re_frame + frame_offset));
 }
 
 
@@ skipping 184 matching lines @@
 void RegExpMacroAssemblerMIPS::CheckStackLimit() {
   ExternalReference stack_limit =
       ExternalReference::address_of_regexp_stack_limit(masm_->isolate());
 
   __ li(a0, Operand(stack_limit));
   __ lw(a0, MemOperand(a0));
   SafeCall(&stack_overflow_label_, ls, backtrack_stackpointer(), Operand(a0));
 }
 
 
-void RegExpMacroAssemblerMIPS::CallCFunctionUsingStub(
-    ExternalReference function,
-    int num_arguments) {
-  // Must pass all arguments in registers. The stub pushes on the stack.
-  ASSERT(num_arguments <= 4);
-  __ li(code_pointer(), Operand(function));
-  RegExpCEntryStub stub;
-  __ CallStub(&stub);
-  if (OS::ActivationFrameAlignment() != 0) {
-    __ lw(sp, MemOperand(sp, 16));
-  }
-  __ li(code_pointer(), Operand(masm_->CodeObject()), CONSTANT_SIZE);
-}
-
-
 void RegExpMacroAssemblerMIPS::LoadCurrentCharacterUnchecked(int cp_offset,
                                                              int characters) {
   Register offset = current_input_offset();
   if (cp_offset != 0) {
     // t7 is not being used to store the capture start index at this point.
     __ Addu(t7, current_input_offset(), Operand(cp_offset * char_size()));
     offset = t7;
   }
   // We assume that we cannot do unaligned loads on MIPS, so this function
   // must only be used to load a single character at a time.
   ASSERT(characters == 1);
   __ Addu(t5, end_of_input_address(), Operand(offset));
   if (mode_ == ASCII) {
     __ lbu(current_character(), MemOperand(t5, 0));
   } else {
     ASSERT(mode_ == UC16);
     __ lhu(current_character(), MemOperand(t5, 0));
   }
 }
 
 
-void RegExpCEntryStub::Generate(MacroAssembler* masm_) {
-  int stack_alignment = OS::ActivationFrameAlignment();
-  if (stack_alignment < kPointerSize) stack_alignment = kPointerSize;
-  // Stack is already aligned for call, so decrement by alignment
-  // to make room for storing the return address.
-  __ Subu(sp, sp, Operand(stack_alignment + kCArgsSlotsSize));
-  const int return_address_offset = kCArgsSlotsSize;
-  __ Addu(a0, sp, return_address_offset);
-  __ sw(ra, MemOperand(a0, 0));
-  __ mov(t9, t1);
-  __ Call(t9);
-  __ lw(ra, MemOperand(sp, return_address_offset));
-  __ Addu(sp, sp, Operand(stack_alignment + kCArgsSlotsSize));
-  __ Jump(ra);
-}
-
-
 #undef __
 
 #endif  // V8_INTERPRETED_REGEXP
 
 }}  // namespace v8::internal
 
 #endif  // V8_TARGET_ARCH_MIPS