MIPS: replace RegExpCEntryStub with DirectCEntryStub.

Port r16618 (0eebc593)

Original commit message:
RegExpCEntryStub is therefore removed.

BUG=none
TEST=none
R=plind44@gmail.com

Review URL: https://codereview.chromium.org/24321002

Patch from Balazs Kilvady <kilvadyb@homejinni.com>.

git-svn-id: http://v8.googlecode.com/svn/branches/bleeding_edge@16927 ce2b1a6d-e550-0410-aec6-3dcde31c8c00

src/mips/code-stubs-mips.cc

@@ -6126,9 +6126,16 @@ void ICCompareStub::GenerateMiss(MacroAssembler* masm) {
 
 
 void DirectCEntryStub::Generate(MacroAssembler* masm) {
-  // No need to pop or drop anything, LeaveExitFrame will restore the old
-  // stack, thus dropping the allocated space for the return value.
-  // The saved ra is after the reserved stack space for the 4 args.
+  // Make place for arguments to fit C calling convention. Most of the callers
+  // of DirectCEntryStub::GenerateCall are using EnterExitFrame/LeaveExitFrame
+  // so they handle stack restoring and we don't have to do that here.
+  // Any caller of DirectCEntryStub::GenerateCall must take care of dropping
+  // kCArgsSlotsSize stack space after the call.
+  __ Subu(sp, sp, Operand(kCArgsSlotsSize));
+  // Place the return address on the stack, making the call
+  // GC safe. The RegExp backend also relies on this.
+  __ sw(ra, MemOperand(sp, kCArgsSlotsSize));
+  __ Call(t9);  // Call the C++ function.
   __ lw(t9, MemOperand(sp, kCArgsSlotsSize));
 
   if (FLAG_debug_code && FLAG_enable_slow_asserts) {
@@ -6145,33 +6152,11 @@ void DirectCEntryStub::Generate(MacroAssembler* masm) {
 
 void DirectCEntryStub::GenerateCall(MacroAssembler* masm,
                                     Register target) {
-  __ Move(t9, target);
-  __ AssertStackIsAligned();
-  // Allocate space for arg slots.
-  __ Subu(sp, sp, kCArgsSlotsSize);
-
-  // Block the trampoline pool through the whole function to make sure the
-  // number of generated instructions is constant.
-  Assembler::BlockTrampolinePoolScope block_trampoline_pool(masm);
-
-  // We need to get the current 'pc' value, which is not available on MIPS.
-  Label find_ra;
-  masm->bal(&find_ra);  // ra = pc + 8.
-  masm->nop();  // Branch delay slot nop.
-  masm->bind(&find_ra);
-
-  const int kNumInstructionsToJump = 6;
-  masm->addiu(ra, ra, kNumInstructionsToJump * kPointerSize);
-  // Push return address (accessible to GC through exit frame pc).
-  // This spot for ra was reserved in EnterExitFrame.
-  masm->sw(ra, MemOperand(sp, kCArgsSlotsSize));
   intptr_t loc =
       reinterpret_cast<intptr_t>(GetCode(masm->isolate()).location());
-  masm->li(ra, Operand(loc, RelocInfo::CODE_TARGET), CONSTANT_SIZE);
-  // Call the function.
-  masm->Jump(t9);
-  // Make sure the stored 'ra' points to this position.
-  ASSERT_EQ(kNumInstructionsToJump, masm->InstructionsGeneratedSince(&find_ra));
+  __ Move(t9, target);
+  __ li(ra, Operand(loc, RelocInfo::CODE_TARGET), CONSTANT_SIZE);
+  __ Call(ra);
 }
 
 

src/mips/code-stubs-mips.h

@@ -455,22 +455,6 @@ class RecordWriteStub: public PlatformCodeStub {
 };
 
 
-// Enter C code from generated RegExp code in a way that allows
-// the C code to fix the return address in case of a GC.
-// Currently only needed on ARM and MIPS.
-class RegExpCEntryStub: public PlatformCodeStub {
- public:
-  RegExpCEntryStub() {}
-  virtual ~RegExpCEntryStub() {}
-  void Generate(MacroAssembler* masm);
-
- private:
-  Major MajorKey() { return RegExpCEntry; }
-  int MinorKey() { return 0; }
-
-  bool NeedsImmovableCode() { return true; }
-};
-
 // Trampoline stub to call into native code. To call safely into native code
 // in the presence of compacting GC (which can move code objects) we need to
 // keep the code which called into native pinned in the memory. Currently the

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

@@ -1063,15 +1063,56 @@ bool RegExpMacroAssemblerMIPS::CanReadUnaligned() {
 // Private methods:
 
 void RegExpMacroAssemblerMIPS::CallCheckStackGuardState(Register scratch) {
-  static const int num_arguments = 3;
-  __ PrepareCallCFunction(num_arguments, scratch);
+  int stack_alignment = OS::ActivationFrameAlignment();
+
+  // Align the stack pointer and save the original sp value on the stack.
+  __ mov(scratch, sp);
+  __ Subu(sp, sp, Operand(kPointerSize));
+  ASSERT(IsPowerOf2(stack_alignment));
+  __ And(sp, sp, Operand(-stack_alignment));
+  __ sw(scratch, MemOperand(sp));
+
   __ 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.
+  ASSERT(IsAligned(stack_alignment, kPointerSize));
+  __ Subu(sp, sp, Operand(stack_alignment));
+
+  // Stack pointer now points to cell where return address is to be written.
+  // Arguments are in registers, meaning we teat the return address as
+  // argument 5. Since DirectCEntryStub will handleallocating space for the C
+  // argument slots, we don't need to care about that here. This is how the
+  // stack will look (sp meaning the value of sp at this moment):
+  // [sp + 3] - empty slot if needed for alignment.
+  // [sp + 2] - saved sp.
+  // [sp + 1] - second word reserved for return value.
+  // [sp + 0] - first word reserved for return value.
+
+  // 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);
+
+  // DirectCEntryStub allocated space for the C argument slots so we have to
+  // drop them with the return address from the stack with loading saved sp.
+  // At this point stack must look:
+  // [sp + 7] - empty slot if needed for alignment.
+  // [sp + 6] - saved sp.
+  // [sp + 5] - second word reserved for return value.
+  // [sp + 4] - first word reserved for return value.
+  // [sp + 3] - C argument slot.
+  // [sp + 2] - C argument slot.
+  // [sp + 1] - C argument slot.
+  // [sp + 0] - C argument slot.
+  __ lw(sp, MemOperand(sp, stack_alignment + kCArgsSlotsSize));
+
+  __ li(code_pointer(), Operand(masm_->CodeObject()));
 }
 
 
@@ -1276,21 +1317,6 @@ 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 +1338,6 @@ 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

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

@@ -217,14 +217,6 @@ class RegExpMacroAssemblerMIPS: public NativeRegExpMacroAssembler {
   // and increments it by a word size.
   inline void Pop(Register target);
 
-  // Calls a C function and cleans up the frame alignment done by
-  // by FrameAlign. The called function *is* allowed to trigger a garbage
-  // collection, but may not take more than four arguments (no arguments
-  // passed on the stack), and the first argument will be a pointer to the
-  // return address.
-  inline void CallCFunctionUsingStub(ExternalReference function,
-                                     int num_arguments);
-
   Isolate* isolate() const { return masm_->isolate(); }
 
   MacroAssembler* masm_;