Fix a bug in Lithium environment iteration.

The Advance() function of the class responsible for iterating
environment uses didn't always advance as far as it could (relying on
the HasNext predicate to finish advancing).  This is brittle.

The HasNext predicate also didn't advance as far as it could when it
was at the end of an environment level.  This is a bug.

R=jkummerow@chromium.org
BUG=
TEST=

Review URL: http://codereview.chromium.org/6993023

git-svn-id: http://v8.googlecode.com/svn/branches/bleeding_edge@8181 ce2b1a6d-e550-0410-aec6-3dcde31c8c00

src/arm/lithium-arm.cc

@@ -68,13 +68,13 @@ void LInstruction::VerifyCall() {
   ASSERT(Output() == NULL ||
          LUnallocated::cast(Output())->HasFixedPolicy() ||
          !LUnallocated::cast(Output())->HasRegisterPolicy());
-  for (UseIterator it(this); it.HasNext(); it.Advance()) {
-    LUnallocated* operand = LUnallocated::cast(it.Next());
+  for (UseIterator it(this); !it.Done(); it.Advance()) {
+    LUnallocated* operand = LUnallocated::cast(it.Current());
     ASSERT(operand->HasFixedPolicy() ||
            operand->IsUsedAtStart());
   }
-  for (TempIterator it(this); it.HasNext(); it.Advance()) {
-    LUnallocated* operand = LUnallocated::cast(it.Next());
+  for (TempIterator it(this); !it.Done(); it.Advance()) {
+    LUnallocated* operand = LUnallocated::cast(it.Current());
     ASSERT(operand->HasFixedPolicy() ||!operand->HasRegisterPolicy());
   }
 }

src/ia32/lithium-ia32.cc

@@ -78,13 +78,13 @@ void LInstruction::VerifyCall() {
   ASSERT(Output() == NULL ||
          LUnallocated::cast(Output())->HasFixedPolicy() ||
          !LUnallocated::cast(Output())->HasRegisterPolicy());
-  for (UseIterator it(this); it.HasNext(); it.Advance()) {
-    LUnallocated* operand = LUnallocated::cast(it.Next());
+  for (UseIterator it(this); !it.Done(); it.Advance()) {
+    LUnallocated* operand = LUnallocated::cast(it.Current());
     ASSERT(operand->HasFixedPolicy() ||
            operand->IsUsedAtStart());
   }
-  for (TempIterator it(this); it.HasNext(); it.Advance()) {
-    LUnallocated* operand = LUnallocated::cast(it.Next());
+  for (TempIterator it(this); !it.Done(); it.Advance()) {
+    LUnallocated* operand = LUnallocated::cast(it.Current());
     ASSERT(operand->HasFixedPolicy() ||!operand->HasRegisterPolicy());
   }
 }

src/lithium-allocator-inl.h

-// Copyright 2010 the V8 project authors. All rights reserved.
+// Copyright 2011 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:
@@ -62,27 +62,27 @@ TempIterator::TempIterator(LInstruction* instr)
     : instr_(instr),
       limit_(instr->TempCount()),
       current_(0) {
-  current_ = AdvanceToNext(0);
+  SkipUninteresting();
 }
 
 
-bool TempIterator::HasNext() { return current_ < limit_; }
+bool TempIterator::Done() { return current_ >= limit_; }
 
 
-LOperand* TempIterator::Next() {
-  ASSERT(HasNext());
+LOperand* TempIterator::Current() {
+  ASSERT(!Done());
   return instr_->TempAt(current_);
 }
 
 
-int TempIterator::AdvanceToNext(int start) {
-  while (start < limit_ && instr_->TempAt(start) == NULL) start++;
-  return start;
+void TempIterator::SkipUninteresting() {
+  while (current_ < limit_ && instr_->TempAt(current_) == NULL) ++current_;
 }
 
 
 void TempIterator::Advance() {
-  current_ = AdvanceToNext(current_ + 1);
+  ++current_;
+  SkipUninteresting();
 }
 
 
@@ -90,27 +90,29 @@ InputIterator::InputIterator(LInstruction* instr)
     : instr_(instr),
       limit_(instr->InputCount()),
       current_(0) {
-  current_ = AdvanceToNext(0);
+  SkipUninteresting();
 }
 
 
-bool InputIterator::HasNext() { return current_ < limit_; }
+bool InputIterator::Done() { return current_ >= limit_; }
 
 
-LOperand* InputIterator::Next() {
-  ASSERT(HasNext());
+LOperand* InputIterator::Current() {
+  ASSERT(!Done());
   return instr_->InputAt(current_);
 }
 
 
 void InputIterator::Advance() {
-  current_ = AdvanceToNext(current_ + 1);
+  ++current_;
+  SkipUninteresting();
 }
 
 
-int InputIterator::AdvanceToNext(int start) {
-  while (start < limit_ && instr_->InputAt(start)->IsConstantOperand()) start++;
-  return start;
+void InputIterator::SkipUninteresting() {
+  while (current_ < limit_ && instr_->InputAt(current_)->IsConstantOperand()) {
+    ++current_;
+  }
 }
 
 
@@ -118,23 +120,23 @@ UseIterator::UseIterator(LInstruction* instr)
     : input_iterator_(instr), env_iterator_(instr->environment()) { }
 
 
-bool UseIterator::HasNext() {
-  return input_iterator_.HasNext() || env_iterator_.HasNext();
+bool UseIterator::Done() {
+  return input_iterator_.Done() && env_iterator_.Done();
 }
 
 
-LOperand* UseIterator::Next() {
-  ASSERT(HasNext());
-  return input_iterator_.HasNext()
-      ? input_iterator_.Next()
-      : env_iterator_.Next();
+LOperand* UseIterator::Current() {
+  ASSERT(!Done());
+  return input_iterator_.Done()
+      ? env_iterator_.Current()
+      : input_iterator_.Current();
 }
 
 
 void UseIterator::Advance() {
-  input_iterator_.HasNext()
-      ? input_iterator_.Advance()
-      : env_iterator_.Advance();
+  input_iterator_.Done()
+      ? env_iterator_.Advance()
+      : input_iterator_.Advance();
 }
 
 } }  // namespace v8::internal

src/lithium-allocator.cc

-// Copyright 2010 the V8 project authors. All rights reserved.
+// Copyright 2011 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:
@@ -800,8 +800,8 @@ void LAllocator::MeetConstraintsBetween(LInstruction* first,
                                         int gap_index) {
   // Handle fixed temporaries.
   if (first != NULL) {
-    for (TempIterator it(first); it.HasNext(); it.Advance()) {
-      LUnallocated* temp = LUnallocated::cast(it.Next());
+    for (TempIterator it(first); !it.Done(); it.Advance()) {
+      LUnallocated* temp = LUnallocated::cast(it.Current());
       if (temp->HasFixedPolicy()) {
         AllocateFixed(temp, gap_index - 1, false);
       }
@@ -842,8 +842,8 @@ void LAllocator::MeetConstraintsBetween(LInstruction* first,
 
   // Handle fixed input operands of second instruction.
   if (second != NULL) {
-    for (UseIterator it(second); it.HasNext(); it.Advance()) {
-      LUnallocated* cur_input = LUnallocated::cast(it.Next());
+    for (UseIterator it(second); !it.Done(); it.Advance()) {
+      LUnallocated* cur_input = LUnallocated::cast(it.Current());
       if (cur_input->HasFixedPolicy()) {
         LUnallocated* input_copy = cur_input->CopyUnconstrained();
         bool is_tagged = HasTaggedValue(cur_input->VirtualRegister());
@@ -978,8 +978,8 @@ void LAllocator::ProcessInstructions(HBasicBlock* block, BitVector* live) {
           }
         }
 
-        for (UseIterator it(instr); it.HasNext(); it.Advance()) {
-          LOperand* input = it.Next();
+        for (UseIterator it(instr); !it.Done(); it.Advance()) {
+          LOperand* input = it.Current();
 
           LifetimePosition use_pos;
           if (input->IsUnallocated() &&
@@ -993,8 +993,8 @@ void LAllocator::ProcessInstructions(HBasicBlock* block, BitVector* live) {
           if (input->IsUnallocated()) live->Add(input->VirtualRegister());
         }
 
-        for (TempIterator it(instr); it.HasNext(); it.Advance()) {
-          LOperand* temp = it.Next();
+        for (TempIterator it(instr); !it.Done(); it.Advance()) {
+          LOperand* temp = it.Current();
           if (instr->IsMarkedAsCall()) {
             if (temp->IsRegister()) continue;
             if (temp->IsUnallocated()) {

src/lithium-allocator.h

@@ -162,12 +162,12 @@ class LEnvironment;
 class TempIterator BASE_EMBEDDED {
  public:
   inline explicit TempIterator(LInstruction* instr);
-  inline bool HasNext();
-  inline LOperand* Next();
+  inline bool Done();
+  inline LOperand* Current();
   inline void Advance();
 
  private:
-  inline int AdvanceToNext(int start);
+  inline void SkipUninteresting();
   LInstruction* instr_;
   int limit_;
   int current_;
@@ -178,12 +178,12 @@ class TempIterator BASE_EMBEDDED {
 class InputIterator BASE_EMBEDDED {
  public:
   inline explicit InputIterator(LInstruction* instr);
-  inline bool HasNext();
-  inline LOperand* Next();
+  inline bool Done();
+  inline LOperand* Current();
   inline void Advance();
 
  private:
-  inline int AdvanceToNext(int start);
+  inline void SkipUninteresting();
   LInstruction* instr_;
   int limit_;
   int current_;
@@ -193,8 +193,8 @@ class InputIterator BASE_EMBEDDED {
 class UseIterator BASE_EMBEDDED {
  public:
   inline explicit UseIterator(LInstruction* instr);
-  inline bool HasNext();
-  inline LOperand* Next();
+  inline bool Done();
+  inline LOperand* Current();
   inline void Advance();
 
  private:

src/lithium.h

@@ -518,34 +518,34 @@ class ShallowIterator BASE_EMBEDDED {
       : env_(env),
         limit_(env != NULL ? env->values()->length() : 0),
         current_(0) {
-    current_ = AdvanceToNext(0);
+    SkipUninteresting();
   }
 
-  inline bool HasNext() {
-    return env_ != NULL && current_ < limit_;
-  }
+  bool Done() { return current_ >= limit_; }
 
-  inline LOperand* Next() {
-    ASSERT(HasNext());
+  LOperand* Current() {
+    ASSERT(!Done());
     return env_->values()->at(current_);
   }
 
-  inline void Advance() {
-    current_ = AdvanceToNext(current_ + 1);
+  void Advance() {
+    ASSERT(!Done());
+    ++current_;
+    SkipUninteresting();
   }
 
-  inline LEnvironment* env() { return env_; }
+  LEnvironment* env() { return env_; }
 
  private:
-  inline bool ShouldSkip(LOperand* op) {
+  bool ShouldSkip(LOperand* op) {
     return op == NULL || op->IsConstantOperand() || op->IsArgument();
   }
 
-  inline int AdvanceToNext(int start) {
-    while (start < limit_ && ShouldSkip(env_->values()->at(start))) {
-      start++;
+  // Skip until something interesting, beginning with and including current_.
+  void SkipUninteresting() {
+    while (current_ < limit_ && ShouldSkip(env_->values()->at(current_))) {
+      ++current_;
     }
-    return start;
   }
 
   LEnvironment* env_;
@@ -558,31 +558,27 @@ class ShallowIterator BASE_EMBEDDED {
 class DeepIterator BASE_EMBEDDED {
  public:
   explicit DeepIterator(LEnvironment* env)
-      : current_iterator_(env) { }
-
-  inline bool HasNext() {
-    if (current_iterator_.HasNext()) return true;
-    if (current_iterator_.env() == NULL) return false;
-    AdvanceToOuter();
-    return current_iterator_.HasNext();
+      : current_iterator_(env) {
+    SkipUninteresting();
   }
 
-  inline LOperand* Next() {
-    ASSERT(current_iterator_.HasNext());
-    return current_iterator_.Next();
+  bool Done() { return current_iterator_.Done(); }
+
+  LOperand* Current() {
+    ASSERT(!current_iterator_.Done());
+    return current_iterator_.Current();
   }
 
-  inline void Advance() {
-    if (current_iterator_.HasNext()) {
-      current_iterator_.Advance();
-    } else {
-      AdvanceToOuter();
-    }
+  void Advance() {
+    current_iterator_.Advance();
+    SkipUninteresting();
   }
 
  private:
-  inline void AdvanceToOuter() {
-    current_iterator_ = ShallowIterator(current_iterator_.env()->outer());
+  void SkipUninteresting() {
+    while (current_iterator_.env() != NULL && current_iterator_.Done()) {
+      current_iterator_ = ShallowIterator(current_iterator_.env()->outer());
+    }
   }
 
   ShallowIterator current_iterator_;

src/x64/lithium-x64.cc

@@ -78,13 +78,13 @@ void LInstruction::VerifyCall() {
   ASSERT(Output() == NULL ||
          LUnallocated::cast(Output())->HasFixedPolicy() ||
          !LUnallocated::cast(Output())->HasRegisterPolicy());
-  for (UseIterator it(this); it.HasNext(); it.Advance()) {
-    LUnallocated* operand = LUnallocated::cast(it.Next());
+  for (UseIterator it(this); !it.Done(); it.Advance()) {
+    LUnallocated* operand = LUnallocated::cast(it.Current());
     ASSERT(operand->HasFixedPolicy() ||
            operand->IsUsedAtStart());
   }
-  for (TempIterator it(this); it.HasNext(); it.Advance()) {
-    LUnallocated* operand = LUnallocated::cast(it.Next());
+  for (TempIterator it(this); !it.Done(); it.Advance()) {
+    LUnallocated* operand = LUnallocated::cast(it.Current());
     ASSERT(operand->HasFixedPolicy() ||!operand->HasRegisterPolicy());
   }
 }

test/mjsunit/regress/regress-1423.js

+// Copyright 2011 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
+//       with the distribution.
+//     * Neither the name of Google Inc. nor the names of its
+//       contributors may be used to endorse or promote products derived
+//       from this software without specific prior written permission.
+//
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+// Flags: --allow-natives-syntax
+
+// Test that the Lithium environment iterator does stop iteration early.
+"use strict";
+
+function f0() {
+  return f1('literal', true);
+}
+
+function f1(x, y) {
+  return f2(x, y);
+}
+
+// Because it's strict, f2 has an environment containing only the constants
+// undefined, 'literal', and false.  Bug 1423 would cause environment
+// iteration to stop early.
+//
+// Bug manifests as UNREACHABLE code (due to an unallocated register) in
+// debug builds.
+function f2(x, y) {
+  if (y) {
+    if (f3(x, 'other-literal')) {
+      return 0;
+    } else {
+      return 1;
+    }
+  } else {
+    return 2;
+  }
+}
+
+function f3(x, y) {
+  return x === y;
+}
+
+for (var i = 0; i < 5; ++i) f0();
+%OptimizeFunctionOnNextCall(f0);
+assertEquals(1, f0());