Improve and simplify removal of unreachable code

src/arm/lithium-codegen-arm.cc

Index: src/arm/lithium-codegen-arm.cc
diff --git a/src/arm/lithium-codegen-arm.cc b/src/arm/lithium-codegen-arm.cc
index e7734c19296f2143f45ac2a83352a4d1e7e49928..396ff1c8a8bc04308374adf3f58ee23e915ef474 100644
--- a/src/arm/lithium-codegen-arm.cc
+++ b/src/arm/lithium-codegen-arm.cc
@@ -98,24 +98,6 @@ void LCodeGen::Abort(BailoutReason reason) {
 }
 
 
-void LCodeGen::Comment(const char* format, ...) {
-  if (!FLAG_code_comments) return;
-  char buffer[4 * KB];
-  StringBuilder builder(buffer, ARRAY_SIZE(buffer));
-  va_list arguments;
-  va_start(arguments, format);
-  builder.AddFormattedList(format, arguments);
-  va_end(arguments);
-
-  // Copy the string before recording it in the assembler to avoid
-  // issues when the stack allocated buffer goes out of scope.
-  size_t length = builder.position();
-  Vector<char> copy = Vector<char>::New(length + 1);
-  OS::MemCopy(copy.start(), builder.Finalize(), copy.length());
-  masm()->RecordComment(copy.start());
-}
-
-
 bool LCodeGen::GeneratePrologue() {
   ASSERT(is_generating());
 
@@ -271,37 +253,6 @@ void LCodeGen::GenerateOsrPrologue() {
 }
 
 
-bool LCodeGen::GenerateBody() {
-  ASSERT(is_generating());
-  bool emit_instructions = true;
-  for (current_instruction_ = 0;
-       !is_aborted() && current_instruction_ < instructions_->length();
-       current_instruction_++) {
-    LInstruction* instr = instructions_->at(current_instruction_);
-
-    // Don't emit code for basic blocks with a replacement.
-    if (instr->IsLabel()) {
-      emit_instructions = !LLabel::cast(instr)->HasReplacement();
-    }
-    if (!emit_instructions) continue;
-
-    if (FLAG_code_comments && instr->HasInterestingComment(this)) {
-      Comment(";;; <@%d,#%d> %s",
-              current_instruction_,
-              instr->hydrogen_value()->id(),
-              instr->Mnemonic());
-    }
-
-    RecordAndUpdatePosition(instr->position());
-
-    instr->CompileToNative(this);
-  }
-  EnsureSpaceForLazyDeopt();
-  last_lazy_deopt_pc_ = masm()->pc_offset();
-  return !is_aborted();
-}
-
-
 bool LCodeGen::GenerateDeferredCode() {
   ASSERT(is_generating());
   if (deferred_.length() > 0) {
@@ -729,7 +680,7 @@ void LCodeGen::CallCodeGeneric(Handle<Code> code,
                                LInstruction* instr,
                                SafepointMode safepoint_mode,
                                TargetAddressStorageMode storage_mode) {
-  EnsureSpaceForLazyDeopt();
+  EnsureSpaceForLazyDeopt(Deoptimizer::patch_size());
   ASSERT(instr != NULL);
   // Block literal pool emission to ensure nop indicating no inlined smi code
   // is in the correct position.
@@ -2187,13 +2138,6 @@ void LCodeGen::DoArithmeticT(LArithmeticT* instr) {
 }
 
 
-int LCodeGen::GetNextEmittedBlock() const {
-  for (int i = current_block_ + 1; i < graph()->blocks()->length(); ++i) {
-    if (!chunk_->GetLabel(i)->HasReplacement()) return i;
-  }
-  return -1;
-}
-
 template<class InstrType>
 void LCodeGen::EmitBranch(InstrType instr, Condition condition) {
   int left_block = instr->TrueDestination(chunk_);
@@ -5633,16 +5577,15 @@ void LCodeGen::EmitIsConstructCall(Register temp1, Register temp2) {
 }
 
 
-void LCodeGen::EnsureSpaceForLazyDeopt() {
+void LCodeGen::EnsureSpaceForLazyDeopt(int space_needed) {
   if (info()->IsStub()) return;
   // Ensure that we have enough space after the previous lazy-bailout
   // instruction for patching the code here.
   int current_pc = masm()->pc_offset();
-  int patch_size = Deoptimizer::patch_size();
-  if (current_pc < last_lazy_deopt_pc_ + patch_size) {
+  if (current_pc < last_lazy_deopt_pc_ + space_needed) {
     // Block literal pool emission for duration of padding.
     Assembler::BlockConstPoolScope block_const_pool(masm());
-    int padding_size = last_lazy_deopt_pc_ + patch_size - current_pc;
+    int padding_size = last_lazy_deopt_pc_ + space_needed - current_pc;
     ASSERT_EQ(0, padding_size % Assembler::kInstrSize);
     while (padding_size > 0) {
       __ nop();
@@ -5653,7 +5596,7 @@ void LCodeGen::EnsureSpaceForLazyDeopt() {
 
 
 void LCodeGen::DoLazyBailout(LLazyBailout* instr) {
-  EnsureSpaceForLazyDeopt();
+  EnsureSpaceForLazyDeopt(Deoptimizer::patch_size());
   last_lazy_deopt_pc_ = masm()->pc_offset();
   ASSERT(instr->HasEnvironment());
   LEnvironment* env = instr->environment();
@@ -5723,7 +5666,7 @@ void LCodeGen::DoStackCheck(LStackCheck* instr) {
     CallCode(isolate()->builtins()->StackCheck(),
               RelocInfo::CODE_TARGET,
               instr);
-    EnsureSpaceForLazyDeopt();
+    EnsureSpaceForLazyDeopt(Deoptimizer::patch_size());
     last_lazy_deopt_pc_ = masm()->pc_offset();
     __ bind(&done);
     RegisterEnvironmentForDeoptimization(env, Safepoint::kLazyDeopt);
@@ -5736,7 +5679,7 @@ void LCodeGen::DoStackCheck(LStackCheck* instr) {
     __ LoadRoot(ip, Heap::kStackLimitRootIndex);
     __ cmp(sp, Operand(ip));
     __ b(lo, deferred_stack_check->entry());
-    EnsureSpaceForLazyDeopt();
+    EnsureSpaceForLazyDeopt(Deoptimizer::patch_size());
     last_lazy_deopt_pc_ = masm()->pc_offset();
     __ bind(instr->done_label());
     deferred_stack_check->SetExit(instr->done_label());