Improve and simplify removal of unreachable code

src/ia32/lithium-codegen-ia32.cc

Index: src/ia32/lithium-codegen-ia32.cc
diff --git a/src/ia32/lithium-codegen-ia32.cc b/src/ia32/lithium-codegen-ia32.cc
index 716c65718f2c3afb76165184e758bf5e21d6d301..14d16c018e0f8ceac3cf0ddaa1646bb06f4e48db 100644
--- a/src/ia32/lithium-codegen-ia32.cc
+++ b/src/ia32/lithium-codegen-ia32.cc
@@ -120,24 +120,6 @@ 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());
-}
-
-
 #ifdef _MSC_VER
 void LCodeGen::MakeSureStackPagesMapped(int offset) {
   const int kPageSize = 4 * KB;
@@ -384,51 +366,27 @@ 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());
-    }
-
-    if (!CpuFeatures::IsSupported(SSE2)) FlushX87StackIfNecessary(instr);
-
-    RecordAndUpdatePosition(instr->position());
+void LCodeGen::GenerateBodyInstructionPre(LInstruction* instr) {
+  if (!CpuFeatures::IsSupported(SSE2)) FlushX87StackIfNecessary(instr);
+}
 
-    instr->CompileToNative(this);
 
-    if (!CpuFeatures::IsSupported(SSE2)) {
-      if (instr->IsGoto()) {
-        x87_stack_.LeavingBlock(current_block_, LGoto::cast(instr));
-      } else if (FLAG_debug_code && FLAG_enable_slow_asserts &&
-                 !instr->IsGap() && !instr->IsReturn()) {
-        if (instr->ClobbersDoubleRegisters()) {
-          if (instr->HasDoubleRegisterResult()) {
-            ASSERT_EQ(1, x87_stack_.depth());
-          } else {
-            ASSERT_EQ(0, x87_stack_.depth());
-          }
+void LCodeGen::GenerateBodyInstructionPost(LInstruction* instr) {
+  if (!CpuFeatures::IsSupported(SSE2)) {
+    if (instr->IsGoto()) {
+      x87_stack_.LeavingBlock(current_block_, LGoto::cast(instr));
+    } else if (FLAG_debug_code && FLAG_enable_slow_asserts &&
+               !instr->IsGap() && !instr->IsReturn()) {
+      if (instr->ClobbersDoubleRegisters()) {
+        if (instr->HasDoubleRegisterResult()) {
+          ASSERT_EQ(1, x87_stack_.depth());
+        } else {
+          ASSERT_EQ(0, x87_stack_.depth());
         }
-        __ VerifyX87StackDepth(x87_stack_.depth());
       }
+      __ VerifyX87StackDepth(x87_stack_.depth());
     }
   }
-  EnsureSpaceForLazyDeopt();
-  return !is_aborted();
 }
 
 
@@ -2342,14 +2300,6 @@ 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 cc) {
   int left_block = instr->TrueDestination(chunk_);
@@ -6194,14 +6144,13 @@ void LCodeGen::EmitIsConstructCall(Register temp) {
 }
 
 
-void LCodeGen::EnsureSpaceForLazyDeopt() {
+void LCodeGen::EnsureSpaceForLazyDeopt(int space_needed) {
   if (!info()->IsStub()) {
     // 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) {
-      int padding_size = last_lazy_deopt_pc_ + patch_size - current_pc;
+    if (current_pc < last_lazy_deopt_pc_ + space_needed) {
+      int padding_size = last_lazy_deopt_pc_ + space_needed - current_pc;
       __ Nop(padding_size);
     }
   }
@@ -6210,7 +6159,7 @@ void LCodeGen::EnsureSpaceForLazyDeopt() {
 
 
 void LCodeGen::DoLazyBailout(LLazyBailout* instr) {
-  EnsureSpaceForLazyDeopt();
+  EnsureSpaceForLazyDeopt(Deoptimizer::patch_size());
   ASSERT(instr->HasEnvironment());
   LEnvironment* env = instr->environment();
   RegisterEnvironmentForDeoptimization(env, Safepoint::kLazyDeopt);
@@ -6281,7 +6230,7 @@ void LCodeGen::DoStackCheck(LStackCheck* instr) {
     CallCode(isolate()->builtins()->StackCheck(),
              RelocInfo::CODE_TARGET,
              instr);
-    EnsureSpaceForLazyDeopt();
+    EnsureSpaceForLazyDeopt(Deoptimizer::patch_size());
     __ bind(&done);
     RegisterEnvironmentForDeoptimization(env, Safepoint::kLazyDeopt);
     safepoints_.RecordLazyDeoptimizationIndex(env->deoptimization_index());
@@ -6294,7 +6243,7 @@ void LCodeGen::DoStackCheck(LStackCheck* instr) {
         ExternalReference::address_of_stack_limit(isolate());
     __ cmp(esp, Operand::StaticVariable(stack_limit));
     __ j(below, deferred_stack_check->entry());
-    EnsureSpaceForLazyDeopt();
+    EnsureSpaceForLazyDeopt(Deoptimizer::patch_size());
     __ bind(instr->done_label());
     deferred_stack_check->SetExit(instr->done_label());
     RegisterEnvironmentForDeoptimization(env, Safepoint::kLazyDeopt);