Improve and simplify removal of unreachable code

src/ia32/lithium-codegen-ia32.cc

 // Copyright 2012 the V8 project authors. All rights reserved.
 // Redistribution and use in source and binary forms, with or without
 // modification, are permitted provided that the following conditions are
 // met:
 //
 //     * Redistributions of source code must retain the above copyright
 //       notice, this list of conditions and the following disclaimer.
 //     * Redistributions in binary form must reproduce the above
 //       copyright notice, this list of conditions and the following
 //       disclaimer in the documentation and/or other materials provided
@@ skipping 102 matching lines @@
   info()->CommitDependencies(code);
 }
 
 
 void LCodeGen::Abort(BailoutReason reason) {
   info()->set_bailout_reason(reason);
   status_ = ABORTED;
 }
 
 
-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;
   for (offset -= kPageSize; offset > 0; offset -= kPageSize) {
     __ mov(Operand(esp, offset), eax);
   }
 }
 #endif
 
 
@@ skipping 226 matching lines @@
   __ mov(alignment_loc, edx);
 
   // Adjust the frame size, subsuming the unoptimized frame into the
   // optimized frame.
   int slots = GetStackSlotCount() - graph()->osr()->UnoptimizedFrameSlots();
   ASSERT(slots >= 1);
   __ sub(esp, Immediate((slots - 1) * kPointerSize));
 }
 
 
-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());
-
-    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());
-          }
-        }
-        __ VerifyX87StackDepth(x87_stack_.depth());
-      }
-    }
-  }
-  EnsureSpaceForLazyDeopt();
-  return !is_aborted();
+void LCodeGen::GenerateBodyInstructionPre(LInstruction* instr) {
+  if (!CpuFeatures::IsSupported(SSE2)) FlushX87StackIfNecessary(instr);
 }
 
 
+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());
+    }
+  }
+}
+
+
 bool LCodeGen::GenerateJumpTable() {
   Label needs_frame;
   if (jump_table_.length() > 0) {
     Comment(";;; -------------------- Jump table --------------------");
   }
   for (int i = 0; i < jump_table_.length(); i++) {
     __ bind(&jump_table_[i].label);
     Address entry = jump_table_[i].address;
     Deoptimizer::BailoutType type = jump_table_[i].bailout_type;
     int id = Deoptimizer::GetDeoptimizationId(isolate(), entry, type);
@@ skipping 1889 matching lines @@
   ASSERT(ToRegister(instr->left()).is(edx));
   ASSERT(ToRegister(instr->right()).is(eax));
   ASSERT(ToRegister(instr->result()).is(eax));
 
   BinaryOpStub stub(instr->op(), NO_OVERWRITE);
   CallCode(stub.GetCode(isolate()), RelocInfo::CODE_TARGET, instr);
   __ nop();  // Signals no inlined code.
 }
 
 
-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_);
   int right_block = instr->FalseDestination(chunk_);
 
   int next_block = GetNextEmittedBlock();
 
   if (right_block == left_block || cc == no_condition) {
     EmitGoto(left_block);
   } else if (left_block == next_block) {
@@ skipping 3824 matching lines @@
   __ j(not_equal, &check_frame_marker, Label::kNear);
   __ mov(temp, Operand(temp, StandardFrameConstants::kCallerFPOffset));
 
   // Check the marker in the calling frame.
   __ bind(&check_frame_marker);
   __ cmp(Operand(temp, StandardFrameConstants::kMarkerOffset),
          Immediate(Smi::FromInt(StackFrame::CONSTRUCT)));
 }
 
 
-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);
     }
   }
   last_lazy_deopt_pc_ = masm()->pc_offset();
 }
 
 
 void LCodeGen::DoLazyBailout(LLazyBailout* instr) {
-  EnsureSpaceForLazyDeopt();
+  EnsureSpaceForLazyDeopt(Deoptimizer::patch_size());
   ASSERT(instr->HasEnvironment());
   LEnvironment* env = instr->environment();
   RegisterEnvironmentForDeoptimization(env, Safepoint::kLazyDeopt);
   safepoints_.RecordLazyDeoptimizationIndex(env->deoptimization_index());
 }
 
 
 void LCodeGen::DoDeoptimize(LDeoptimize* instr) {
   Deoptimizer::BailoutType type = instr->hydrogen()->type();
   // TODO(danno): Stubs expect all deopts to be lazy for historical reasons (the
@@ skipping 50 matching lines @@
     ExternalReference stack_limit =
         ExternalReference::address_of_stack_limit(isolate());
     __ cmp(esp, Operand::StaticVariable(stack_limit));
     __ j(above_equal, &done, Label::kNear);
 
     ASSERT(instr->context()->IsRegister());
     ASSERT(ToRegister(instr->context()).is(esi));
     CallCode(isolate()->builtins()->StackCheck(),
              RelocInfo::CODE_TARGET,
              instr);
-    EnsureSpaceForLazyDeopt();
+    EnsureSpaceForLazyDeopt(Deoptimizer::patch_size());
     __ bind(&done);
     RegisterEnvironmentForDeoptimization(env, Safepoint::kLazyDeopt);
     safepoints_.RecordLazyDeoptimizationIndex(env->deoptimization_index());
   } else {
     ASSERT(instr->hydrogen()->is_backwards_branch());
     // Perform stack overflow check if this goto needs it before jumping.
     DeferredStackCheck* deferred_stack_check =
         new(zone()) DeferredStackCheck(this, instr, x87_stack_);
     ExternalReference stack_limit =
         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);
     // Don't record a deoptimization index for the safepoint here.
     // This will be done explicitly when emitting call and the safepoint in
     // the deferred code.
   }
 }
 
 
@@ skipping 97 matching lines @@
                               FixedArray::kHeaderSize - kPointerSize));
   __ bind(&done);
 }
 
 
 #undef __
 
 } }  // namespace v8::internal
 
 #endif  // V8_TARGET_ARCH_IA32