src/v8/src/mips/deoptimizer-mips.cc - cobalt - Git at Google

 // Copyright 2011 the V8 project authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.

 #include "src/assembler-inl.h"
 #include "src/deoptimizer.h"
 #include "src/register-configuration.h"
 #include "src/safepoint-table.h"

 namespace v8 {
 namespace internal {


 #define __ masm()->


 // This code tries to be close to ia32 code so that any changes can be
 // easily ported.
 void Deoptimizer::TableEntryGenerator::Generate() {
   GeneratePrologue();

   // Unlike on ARM we don't save all the registers, just the useful ones.
   // For the rest, there are gaps on the stack, so the offsets remain the same.
   const int kNumberOfRegisters = Register::kNumRegisters;

   RegList restored_regs = kJSCallerSaved | kCalleeSaved;
   RegList saved_regs = restored_regs | sp.bit() | ra.bit();

   const int kDoubleRegsSize = kDoubleSize * DoubleRegister::kNumRegisters;
   const int kFloatRegsSize = kFloatSize * FloatRegister::kNumRegisters;

   // Save all FPU registers before messing with them.
   __ Subu(sp, sp, Operand(kDoubleRegsSize));
   const RegisterConfiguration* config = RegisterConfiguration::Default();
   for (int i = 0; i < config->num_allocatable_double_registers(); ++i) {
     int code = config->GetAllocatableDoubleCode(i);
     const DoubleRegister fpu_reg = DoubleRegister::from_code(code);
     int offset = code * kDoubleSize;
     __ Sdc1(fpu_reg, MemOperand(sp, offset));
   }

   __ Subu(sp, sp, Operand(kFloatRegsSize));
   for (int i = 0; i < config->num_allocatable_float_registers(); ++i) {
     int code = config->GetAllocatableFloatCode(i);
     const FloatRegister fpu_reg = FloatRegister::from_code(code);
     int offset = code * kFloatSize;
     __ swc1(fpu_reg, MemOperand(sp, offset));
   }

   // Push saved_regs (needed to populate FrameDescription::registers_).
   // Leave gaps for other registers.
   __ Subu(sp, sp, kNumberOfRegisters * kPointerSize);
   for (int16_t i = kNumberOfRegisters - 1; i >= 0; i--) {
     if ((saved_regs & (1 << i)) != 0) {
       __ sw(ToRegister(i), MemOperand(sp, kPointerSize * i));
     }
   }

   __ li(a2, Operand(ExternalReference(IsolateAddressId::kCEntryFPAddress,
                                       isolate())));
   __ sw(fp, MemOperand(a2));

   const int kSavedRegistersAreaSize =
       (kNumberOfRegisters * kPointerSize) + kDoubleRegsSize + kFloatRegsSize;

   // Get the bailout id from the stack.
   __ lw(a2, MemOperand(sp, kSavedRegistersAreaSize));

   // Get the address of the location in the code object (a3) (return
   // address for lazy deoptimization) and compute the fp-to-sp delta in
   // register t0.
   __ mov(a3, ra);
   // Correct one word for bailout id.
   __ Addu(t0, sp, Operand(kSavedRegistersAreaSize + (1 * kPointerSize)));

   __ Subu(t0, fp, t0);

   // Allocate a new deoptimizer object.
   __ PrepareCallCFunction(6, t1);
   // Pass four arguments in a0 to a3 and fifth & sixth arguments on stack.
   __ mov(a0, zero_reg);
   Label context_check;
   __ lw(a1, MemOperand(fp, CommonFrameConstants::kContextOrFrameTypeOffset));
   __ JumpIfSmi(a1, &context_check);
   __ lw(a0, MemOperand(fp, JavaScriptFrameConstants::kFunctionOffset));
   __ bind(&context_check);
   __ li(a1, Operand(type()));  // Bailout type.
   // a2: bailout id already loaded.
   // a3: code address or 0 already loaded.
   __ sw(t0, CFunctionArgumentOperand(5));  // Fp-to-sp delta.
   __ li(t1, Operand(ExternalReference::isolate_address(isolate())));
   __ sw(t1, CFunctionArgumentOperand(6));  // Isolate.
   // Call Deoptimizer::New().
   {
     AllowExternalCallThatCantCauseGC scope(masm());
     __ CallCFunction(ExternalReference::new_deoptimizer_function(isolate()), 6);
   }

   // Preserve "deoptimizer" object in register v0 and get the input
   // frame descriptor pointer to a1 (deoptimizer->input_);
   // Move deopt-obj to a0 for call to Deoptimizer::ComputeOutputFrames() below.
   __ mov(a0, v0);
   __ lw(a1, MemOperand(v0, Deoptimizer::input_offset()));

   // Copy core registers into FrameDescription::registers_[kNumRegisters].
   DCHECK_EQ(Register::kNumRegisters, kNumberOfRegisters);
   for (int i = 0; i < kNumberOfRegisters; i++) {
     int offset = (i * kPointerSize) + FrameDescription::registers_offset();
     if ((saved_regs & (1 << i)) != 0) {
       __ lw(a2, MemOperand(sp, i * kPointerSize));
       __ sw(a2, MemOperand(a1, offset));
     } else if (FLAG_debug_code) {
       __ li(a2, kDebugZapValue);
       __ sw(a2, MemOperand(a1, offset));
     }
   }

   int double_regs_offset = FrameDescription::double_registers_offset();
   // Copy FPU registers to
   // double_registers_[DoubleRegister::kNumAllocatableRegisters]
   for (int i = 0; i < config->num_allocatable_double_registers(); ++i) {
     int code = config->GetAllocatableDoubleCode(i);
     int dst_offset = code * kDoubleSize + double_regs_offset;
     int src_offset =
         code * kDoubleSize + kNumberOfRegisters * kPointerSize + kFloatRegsSize;
     __ Ldc1(f0, MemOperand(sp, src_offset));
     __ Sdc1(f0, MemOperand(a1, dst_offset));
   }

   // Copy FPU registers to
   // float_registers_[FloatRegister::kNumAllocatableRegisters]
   int float_regs_offset = FrameDescription::float_registers_offset();
   for (int i = 0; i < config->num_allocatable_float_registers(); ++i) {
     int code = config->GetAllocatableFloatCode(i);
     int dst_offset = code * kFloatSize + float_regs_offset;
     int src_offset = code * kFloatSize + kNumberOfRegisters * kPointerSize;
     __ lwc1(f0, MemOperand(sp, src_offset));
     __ swc1(f0, MemOperand(a1, dst_offset));
   }

   // Remove the bailout id and the saved registers from the stack.
   __ Addu(sp, sp, Operand(kSavedRegistersAreaSize + (1 * kPointerSize)));

   // Compute a pointer to the unwinding limit in register a2; that is
   // the first stack slot not part of the input frame.
   __ lw(a2, MemOperand(a1, FrameDescription::frame_size_offset()));
   __ Addu(a2, a2, sp);

   // Unwind the stack down to - but not including - the unwinding
   // limit and copy the contents of the activation frame to the input
   // frame description.
   __ Addu(a3, a1, Operand(FrameDescription::frame_content_offset()));
   Label pop_loop;
   Label pop_loop_header;
   __ BranchShort(&pop_loop_header);
   __ bind(&pop_loop);
   __ pop(t0);
   __ sw(t0, MemOperand(a3, 0));
   __ addiu(a3, a3, sizeof(uint32_t));
   __ bind(&pop_loop_header);
   __ BranchShort(&pop_loop, ne, a2, Operand(sp));

   // Compute the output frame in the deoptimizer.
   __ push(a0);  // Preserve deoptimizer object across call.
   // a0: deoptimizer object; a1: scratch.
   __ PrepareCallCFunction(1, a1);
   // Call Deoptimizer::ComputeOutputFrames().
   {
     AllowExternalCallThatCantCauseGC scope(masm());
     __ CallCFunction(
         ExternalReference::compute_output_frames_function(isolate()), 1);
   }
   __ pop(a0);  // Restore deoptimizer object (class Deoptimizer).

   __ lw(sp, MemOperand(a0, Deoptimizer::caller_frame_top_offset()));

   // Replace the current (input) frame with the output frames.
   Label outer_push_loop, inner_push_loop,
       outer_loop_header, inner_loop_header;
   // Outer loop state: t0 = current "FrameDescription** output_",
   // a1 = one past the last FrameDescription**.
   __ lw(a1, MemOperand(a0, Deoptimizer::output_count_offset()));
   __ lw(t0, MemOperand(a0, Deoptimizer::output_offset()));  // t0 is output_.
   __ Lsa(a1, t0, a1, kPointerSizeLog2);
   __ BranchShort(&outer_loop_header);
   __ bind(&outer_push_loop);
   // Inner loop state: a2 = current FrameDescription*, a3 = loop index.
   __ lw(a2, MemOperand(t0, 0));  // output_[ix]
   __ lw(a3, MemOperand(a2, FrameDescription::frame_size_offset()));
   __ BranchShort(&inner_loop_header);
   __ bind(&inner_push_loop);
   __ Subu(a3, a3, Operand(sizeof(uint32_t)));
   __ Addu(t2, a2, Operand(a3));
   __ lw(t3, MemOperand(t2, FrameDescription::frame_content_offset()));
   __ push(t3);
   __ bind(&inner_loop_header);
   __ BranchShort(&inner_push_loop, ne, a3, Operand(zero_reg));

   __ Addu(t0, t0, Operand(kPointerSize));
   __ bind(&outer_loop_header);
   __ BranchShort(&outer_push_loop, lt, t0, Operand(a1));

   __ lw(a1, MemOperand(a0, Deoptimizer::input_offset()));
   for (int i = 0; i < config->num_allocatable_double_registers(); ++i) {
     int code = config->GetAllocatableDoubleCode(i);
     const DoubleRegister fpu_reg = DoubleRegister::from_code(code);
     int src_offset = code * kDoubleSize + double_regs_offset;
     __ Ldc1(fpu_reg, MemOperand(a1, src_offset));
   }

   // Push pc and continuation from the last output frame.
   __ lw(t2, MemOperand(a2, FrameDescription::pc_offset()));
   __ push(t2);
   __ lw(t2, MemOperand(a2, FrameDescription::continuation_offset()));
   __ push(t2);


   // Technically restoring 'at' should work unless zero_reg is also restored
   // but it's safer to check for this.
   DCHECK(!(at.bit() & restored_regs));
   // Restore the registers from the last output frame.
   __ mov(at, a2);
   for (int i = kNumberOfRegisters - 1; i >= 0; i--) {
     int offset = (i * kPointerSize) + FrameDescription::registers_offset();
     if ((restored_regs & (1 << i)) != 0) {
       __ lw(ToRegister(i), MemOperand(at, offset));
     }
   }

   __ InitializeRootRegister();

   __ pop(at);  // Get continuation, leave pc on stack.
   __ pop(ra);
   __ Jump(at);
   __ stop("Unreachable.");
 }


 // Maximum size of a table entry generated below.
 #ifdef _MIPS_ARCH_MIPS32R6
 const int Deoptimizer::table_entry_size_ = 2 * Assembler::kInstrSize;
 #else
 const int Deoptimizer::table_entry_size_ = 3 * Assembler::kInstrSize;
 #endif

 void Deoptimizer::TableEntryGenerator::GeneratePrologue() {
   Assembler::BlockTrampolinePoolScope block_trampoline_pool(masm());

   // Create a sequence of deoptimization entries.
   // Note that registers are still live when jumping to an entry.
   Label table_start, done, trampoline_jump;
   __ bind(&table_start);

 #ifdef _MIPS_ARCH_MIPS32R6
   int kMaxEntriesBranchReach =
       (1 << (kImm26Bits - 2)) / (table_entry_size_ / Assembler::kInstrSize);
 #else
   int kMaxEntriesBranchReach = (1 << (kImm16Bits - 2))/
      (table_entry_size_ /  Assembler::kInstrSize);
 #endif

   if (count() <= kMaxEntriesBranchReach) {
     // Common case.
     for (int i = 0; i < count(); i++) {
       Label start;
       __ bind(&start);
       DCHECK(is_int16(i));
       if (IsMipsArchVariant(kMips32r6)) {
         __ li(at, i);
         __ BranchShort(PROTECT, &done);
       } else {
         __ BranchShort(USE_DELAY_SLOT, &done);  // Expose delay slot.
         __ li(at, i);                           // In the delay slot.
         __ nop();
       }
       DCHECK_EQ(table_entry_size_, masm()->SizeOfCodeGeneratedSince(&start));
     }

     DCHECK_EQ(masm()->SizeOfCodeGeneratedSince(&table_start),
         count() * table_entry_size_);
     __ bind(&done);
     __ Push(at);
   } else {
     DCHECK(!IsMipsArchVariant(kMips32r6));
     // Uncommon case, the branch cannot reach.
     // Create mini trampoline to reach the end of the table
     for (int i = 0, j = 0; i < count(); i++, j++) {
       Label start;
       __ bind(&start);
       DCHECK(is_int16(i));
       if (j >= kMaxEntriesBranchReach) {
         j = 0;
         __ li(at, i);
         __ bind(&trampoline_jump);
         trampoline_jump = Label();
         __ BranchShort(USE_DELAY_SLOT, &trampoline_jump);
         __ nop();
       } else {
         __ BranchShort(USE_DELAY_SLOT, &trampoline_jump);  // Expose delay slot.
         __ li(at, i);                                      // In the delay slot.
         __ nop();
       }
       DCHECK_EQ(table_entry_size_, masm()->SizeOfCodeGeneratedSince(&start));
     }

     DCHECK_EQ(masm()->SizeOfCodeGeneratedSince(&table_start),
         count() * table_entry_size_);
     __ bind(&trampoline_jump);
     __ Push(at);
   }
 }

 bool Deoptimizer::PadTopOfStackRegister() { return false; }

 void FrameDescription::SetCallerPc(unsigned offset, intptr_t value) {
   SetFrameSlot(offset, value);
 }


 void FrameDescription::SetCallerFp(unsigned offset, intptr_t value) {
   SetFrameSlot(offset, value);
 }


 void FrameDescription::SetCallerConstantPool(unsigned offset, intptr_t value) {
   // No embedded constant pool support.
   UNREACHABLE();
 }


 #undef __


 }  // namespace internal
 }  // namespace v8
	// Copyright 2011 the V8 project authors. All rights reserved.
	// Use of this source code is governed by a BSD-style license that can be
	// found in the LICENSE file.

	#include "src/assembler-inl.h"
	#include "src/deoptimizer.h"
	#include "src/register-configuration.h"
	#include "src/safepoint-table.h"

	namespace v8 {
	namespace internal {


	#define __ masm()->


	// This code tries to be close to ia32 code so that any changes can be
	// easily ported.
	void Deoptimizer::TableEntryGenerator::Generate() {
	GeneratePrologue();

	// Unlike on ARM we don't save all the registers, just the useful ones.
	// For the rest, there are gaps on the stack, so the offsets remain the same.
	const int kNumberOfRegisters = Register::kNumRegisters;

	RegList restored_regs = kJSCallerSaved \| kCalleeSaved;
	RegList saved_regs = restored_regs \| sp.bit() \| ra.bit();

	const int kDoubleRegsSize = kDoubleSize * DoubleRegister::kNumRegisters;
	const int kFloatRegsSize = kFloatSize * FloatRegister::kNumRegisters;

	// Save all FPU registers before messing with them.
	__ Subu(sp, sp, Operand(kDoubleRegsSize));
	const RegisterConfiguration* config = RegisterConfiguration::Default();
	for (int i = 0; i < config->num_allocatable_double_registers(); ++i) {
	int code = config->GetAllocatableDoubleCode(i);
	const DoubleRegister fpu_reg = DoubleRegister::from_code(code);
	int offset = code * kDoubleSize;
	__ Sdc1(fpu_reg, MemOperand(sp, offset));
	}

	__ Subu(sp, sp, Operand(kFloatRegsSize));
	for (int i = 0; i < config->num_allocatable_float_registers(); ++i) {
	int code = config->GetAllocatableFloatCode(i);
	const FloatRegister fpu_reg = FloatRegister::from_code(code);
	int offset = code * kFloatSize;
	__ swc1(fpu_reg, MemOperand(sp, offset));
	}

	// Push saved_regs (needed to populate FrameDescription::registers_).
	// Leave gaps for other registers.
	__ Subu(sp, sp, kNumberOfRegisters * kPointerSize);
	for (int16_t i = kNumberOfRegisters - 1; i >= 0; i--) {
	if ((saved_regs & (1 << i)) != 0) {
	__ sw(ToRegister(i), MemOperand(sp, kPointerSize * i));
	}
	}

	__ li(a2, Operand(ExternalReference(IsolateAddressId::kCEntryFPAddress,
	isolate())));
	__ sw(fp, MemOperand(a2));

	const int kSavedRegistersAreaSize =
	(kNumberOfRegisters * kPointerSize) + kDoubleRegsSize + kFloatRegsSize;

	// Get the bailout id from the stack.
	__ lw(a2, MemOperand(sp, kSavedRegistersAreaSize));

	// Get the address of the location in the code object (a3) (return
	// address for lazy deoptimization) and compute the fp-to-sp delta in
	// register t0.
	__ mov(a3, ra);
	// Correct one word for bailout id.
	__ Addu(t0, sp, Operand(kSavedRegistersAreaSize + (1 * kPointerSize)));

	__ Subu(t0, fp, t0);

	// Allocate a new deoptimizer object.
	__ PrepareCallCFunction(6, t1);
	// Pass four arguments in a0 to a3 and fifth & sixth arguments on stack.
	__ mov(a0, zero_reg);
	Label context_check;
	__ lw(a1, MemOperand(fp, CommonFrameConstants::kContextOrFrameTypeOffset));
	__ JumpIfSmi(a1, &context_check);
	__ lw(a0, MemOperand(fp, JavaScriptFrameConstants::kFunctionOffset));
	__ bind(&context_check);
	__ li(a1, Operand(type())); // Bailout type.
	// a2: bailout id already loaded.
	// a3: code address or 0 already loaded.
	__ sw(t0, CFunctionArgumentOperand(5)); // Fp-to-sp delta.
	__ li(t1, Operand(ExternalReference::isolate_address(isolate())));
	__ sw(t1, CFunctionArgumentOperand(6)); // Isolate.
	// Call Deoptimizer::New().
	{
	AllowExternalCallThatCantCauseGC scope(masm());
	__ CallCFunction(ExternalReference::new_deoptimizer_function(isolate()), 6);
	}

	// Preserve "deoptimizer" object in register v0 and get the input
	// frame descriptor pointer to a1 (deoptimizer->input_);
	// Move deopt-obj to a0 for call to Deoptimizer::ComputeOutputFrames() below.
	__ mov(a0, v0);
	__ lw(a1, MemOperand(v0, Deoptimizer::input_offset()));

	// Copy core registers into FrameDescription::registers_[kNumRegisters].
	DCHECK_EQ(Register::kNumRegisters, kNumberOfRegisters);
	for (int i = 0; i < kNumberOfRegisters; i++) {
	int offset = (i * kPointerSize) + FrameDescription::registers_offset();
	if ((saved_regs & (1 << i)) != 0) {
	__ lw(a2, MemOperand(sp, i * kPointerSize));
	__ sw(a2, MemOperand(a1, offset));
	} else if (FLAG_debug_code) {
	__ li(a2, kDebugZapValue);
	__ sw(a2, MemOperand(a1, offset));
	}
	}

	int double_regs_offset = FrameDescription::double_registers_offset();
	// Copy FPU registers to
	// double_registers_[DoubleRegister::kNumAllocatableRegisters]
	for (int i = 0; i < config->num_allocatable_double_registers(); ++i) {
	int code = config->GetAllocatableDoubleCode(i);
	int dst_offset = code * kDoubleSize + double_regs_offset;
	int src_offset =
	code * kDoubleSize + kNumberOfRegisters * kPointerSize + kFloatRegsSize;
	__ Ldc1(f0, MemOperand(sp, src_offset));
	__ Sdc1(f0, MemOperand(a1, dst_offset));
	}

	// Copy FPU registers to
	// float_registers_[FloatRegister::kNumAllocatableRegisters]
	int float_regs_offset = FrameDescription::float_registers_offset();
	for (int i = 0; i < config->num_allocatable_float_registers(); ++i) {
	int code = config->GetAllocatableFloatCode(i);
	int dst_offset = code * kFloatSize + float_regs_offset;
	int src_offset = code * kFloatSize + kNumberOfRegisters * kPointerSize;
	__ lwc1(f0, MemOperand(sp, src_offset));
	__ swc1(f0, MemOperand(a1, dst_offset));
	}

	// Remove the bailout id and the saved registers from the stack.
	__ Addu(sp, sp, Operand(kSavedRegistersAreaSize + (1 * kPointerSize)));

	// Compute a pointer to the unwinding limit in register a2; that is
	// the first stack slot not part of the input frame.
	__ lw(a2, MemOperand(a1, FrameDescription::frame_size_offset()));
	__ Addu(a2, a2, sp);

	// Unwind the stack down to - but not including - the unwinding
	// limit and copy the contents of the activation frame to the input
	// frame description.
	__ Addu(a3, a1, Operand(FrameDescription::frame_content_offset()));
	Label pop_loop;
	Label pop_loop_header;
	__ BranchShort(&pop_loop_header);
	__ bind(&pop_loop);
	__ pop(t0);
	__ sw(t0, MemOperand(a3, 0));
	__ addiu(a3, a3, sizeof(uint32_t));
	__ bind(&pop_loop_header);
	__ BranchShort(&pop_loop, ne, a2, Operand(sp));

	// Compute the output frame in the deoptimizer.
	__ push(a0); // Preserve deoptimizer object across call.
	// a0: deoptimizer object; a1: scratch.
	__ PrepareCallCFunction(1, a1);
	// Call Deoptimizer::ComputeOutputFrames().
	{
	AllowExternalCallThatCantCauseGC scope(masm());
	__ CallCFunction(
	ExternalReference::compute_output_frames_function(isolate()), 1);
	}
	__ pop(a0); // Restore deoptimizer object (class Deoptimizer).

	__ lw(sp, MemOperand(a0, Deoptimizer::caller_frame_top_offset()));

	// Replace the current (input) frame with the output frames.
	Label outer_push_loop, inner_push_loop,
	outer_loop_header, inner_loop_header;
	// Outer loop state: t0 = current "FrameDescription** output_",
	// a1 = one past the last FrameDescription**.
	__ lw(a1, MemOperand(a0, Deoptimizer::output_count_offset()));
	__ lw(t0, MemOperand(a0, Deoptimizer::output_offset())); // t0 is output_.
	__ Lsa(a1, t0, a1, kPointerSizeLog2);
	__ BranchShort(&outer_loop_header);
	__ bind(&outer_push_loop);
	// Inner loop state: a2 = current FrameDescription*, a3 = loop index.
	__ lw(a2, MemOperand(t0, 0)); // output_[ix]
	__ lw(a3, MemOperand(a2, FrameDescription::frame_size_offset()));
	__ BranchShort(&inner_loop_header);
	__ bind(&inner_push_loop);
	__ Subu(a3, a3, Operand(sizeof(uint32_t)));
	__ Addu(t2, a2, Operand(a3));
	__ lw(t3, MemOperand(t2, FrameDescription::frame_content_offset()));
	__ push(t3);
	__ bind(&inner_loop_header);
	__ BranchShort(&inner_push_loop, ne, a3, Operand(zero_reg));

	__ Addu(t0, t0, Operand(kPointerSize));
	__ bind(&outer_loop_header);
	__ BranchShort(&outer_push_loop, lt, t0, Operand(a1));

	__ lw(a1, MemOperand(a0, Deoptimizer::input_offset()));
	for (int i = 0; i < config->num_allocatable_double_registers(); ++i) {
	int code = config->GetAllocatableDoubleCode(i);
	const DoubleRegister fpu_reg = DoubleRegister::from_code(code);
	int src_offset = code * kDoubleSize + double_regs_offset;
	__ Ldc1(fpu_reg, MemOperand(a1, src_offset));
	}

	// Push pc and continuation from the last output frame.
	__ lw(t2, MemOperand(a2, FrameDescription::pc_offset()));
	__ push(t2);
	__ lw(t2, MemOperand(a2, FrameDescription::continuation_offset()));
	__ push(t2);


	// Technically restoring 'at' should work unless zero_reg is also restored
	// but it's safer to check for this.
	DCHECK(!(at.bit() & restored_regs));
	// Restore the registers from the last output frame.
	__ mov(at, a2);
	for (int i = kNumberOfRegisters - 1; i >= 0; i--) {
	int offset = (i * kPointerSize) + FrameDescription::registers_offset();
	if ((restored_regs & (1 << i)) != 0) {
	__ lw(ToRegister(i), MemOperand(at, offset));
	}
	}

	__ InitializeRootRegister();

	__ pop(at); // Get continuation, leave pc on stack.
	__ pop(ra);
	__ Jump(at);
	__ stop("Unreachable.");
	}


	// Maximum size of a table entry generated below.
	#ifdef _MIPS_ARCH_MIPS32R6
	const int Deoptimizer::table_entry_size_ = 2 * Assembler::kInstrSize;
	#else
	const int Deoptimizer::table_entry_size_ = 3 * Assembler::kInstrSize;
	#endif

	void Deoptimizer::TableEntryGenerator::GeneratePrologue() {
	Assembler::BlockTrampolinePoolScope block_trampoline_pool(masm());

	// Create a sequence of deoptimization entries.
	// Note that registers are still live when jumping to an entry.
	Label table_start, done, trampoline_jump;
	__ bind(&table_start);

	#ifdef _MIPS_ARCH_MIPS32R6
	int kMaxEntriesBranchReach =
	(1 << (kImm26Bits - 2)) / (table_entry_size_ / Assembler::kInstrSize);
	#else
	int kMaxEntriesBranchReach = (1 << (kImm16Bits - 2))/
	(table_entry_size_ / Assembler::kInstrSize);
	#endif

	if (count() <= kMaxEntriesBranchReach) {
	// Common case.
	for (int i = 0; i < count(); i++) {
	Label start;
	__ bind(&start);
	DCHECK(is_int16(i));
	if (IsMipsArchVariant(kMips32r6)) {
	__ li(at, i);
	__ BranchShort(PROTECT, &done);
	} else {
	__ BranchShort(USE_DELAY_SLOT, &done); // Expose delay slot.
	__ li(at, i); // In the delay slot.
	__ nop();
	}
	DCHECK_EQ(table_entry_size_, masm()->SizeOfCodeGeneratedSince(&start));
	}

	DCHECK_EQ(masm()->SizeOfCodeGeneratedSince(&table_start),
	count() * table_entry_size_);
	__ bind(&done);
	__ Push(at);
	} else {
	DCHECK(!IsMipsArchVariant(kMips32r6));
	// Uncommon case, the branch cannot reach.
	// Create mini trampoline to reach the end of the table
	for (int i = 0, j = 0; i < count(); i++, j++) {
	Label start;
	__ bind(&start);
	DCHECK(is_int16(i));
	if (j >= kMaxEntriesBranchReach) {
	j = 0;
	__ li(at, i);
	__ bind(&trampoline_jump);
	trampoline_jump = Label();
	__ BranchShort(USE_DELAY_SLOT, &trampoline_jump);
	__ nop();
	} else {
	__ BranchShort(USE_DELAY_SLOT, &trampoline_jump); // Expose delay slot.
	__ li(at, i); // In the delay slot.
	__ nop();
	}
	DCHECK_EQ(table_entry_size_, masm()->SizeOfCodeGeneratedSince(&start));
	}

	DCHECK_EQ(masm()->SizeOfCodeGeneratedSince(&table_start),
	count() * table_entry_size_);
	__ bind(&trampoline_jump);
	__ Push(at);
	}
	}

	bool Deoptimizer::PadTopOfStackRegister() { return false; }

	void FrameDescription::SetCallerPc(unsigned offset, intptr_t value) {
	SetFrameSlot(offset, value);
	}


	void FrameDescription::SetCallerFp(unsigned offset, intptr_t value) {
	SetFrameSlot(offset, value);
	}


	void FrameDescription::SetCallerConstantPool(unsigned offset, intptr_t value) {
	// No embedded constant pool support.
	UNREACHABLE();
	}


	#undef __


	} // namespace internal
	} // namespace v8