MIPS: replace RegExpCEntryStub with DirectCEntryStub.

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

Index: src/mips/regexp-macro-assembler-mips.cc
diff --git a/src/mips/regexp-macro-assembler-mips.cc b/src/mips/regexp-macro-assembler-mips.cc
index 1a04fd10292b2532256bcecc315ff4ecadf263b5..225b090b979b2bd108b73802de0ba382356cfb85 100644
--- a/src/mips/regexp-macro-assembler-mips.cc
+++ b/src/mips/regexp-macro-assembler-mips.cc
@@ -1063,15 +1063,32 @@ bool RegExpMacroAssemblerMIPS::CanReadUnaligned() {
 // 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()));
 }
 
 
@@ -1276,21 +1293,6 @@ void RegExpMacroAssemblerMIPS::CheckStackLimit() {
 }
 
 
-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();
@@ -1312,23 +1314,6 @@ void RegExpMacroAssemblerMIPS::LoadCurrentCharacterUnchecked(int cp_offset,
 }
 
 
-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