Do not eagerly update allow_osr_at_loop_nesting_level.

Having debug break points prevents OSR. That causes
allow_osr_at_loop_nesting_level and the actually patched state
to go out of sync.

R=jkummerow@chromium.org
BUG=387599
LOG=Y

Review URL: https://codereview.chromium.org/346223007

git-svn-id: https://v8.googlecode.com/svn/branches/bleeding_edge@21958 ce2b1a6d-e550-0410-aec6-3dcde31c8c00

src/full-codegen.cc

@@ -328,7 +328,6 @@ bool FullCodeGenerator::MakeCode(CompilationInfo* info) {
   code->set_allow_osr_at_loop_nesting_level(0);
   code->set_profiler_ticks(0);
   code->set_back_edge_table_offset(table_offset);
-  code->set_back_edges_patched_for_osr(false);
   CodeGenerator::PrintCode(code, info);
   info->SetCode(code);
 #ifdef ENABLE_GDB_JIT_INTERFACE
@@ -348,7 +347,7 @@ unsigned FullCodeGenerator::EmitBackEdgeTable() {
   // The back edge table consists of a length (in number of entries)
   // field, and then a sequence of entries.  Each entry is a pair of AST id
   // and code-relative pc offset.
-  masm()->Align(kIntSize);
+  masm()->Align(kPointerSize);
   unsigned offset = masm()->pc_offset();
   unsigned length = back_edges_.length();
   __ dd(length);
@@ -1617,9 +1616,11 @@ void BackEdgeTable::Patch(Isolate* isolate, Code* unoptimized) {
   DisallowHeapAllocation no_gc;
   Code* patch = isolate->builtins()->builtin(Builtins::kOnStackReplacement);
 
-  // Iterate over the back edge table and patch every interrupt
+  // Increment loop nesting level by one and iterate over the back edge table
+  // to find the matching loops to patch the interrupt
   // call to an unconditional call to the replacement code.
-  int loop_nesting_level = unoptimized->allow_osr_at_loop_nesting_level();
+  int loop_nesting_level = unoptimized->allow_osr_at_loop_nesting_level() + 1;
+  if (loop_nesting_level > Code::kMaxLoopNestingMarker) return;
 
   BackEdgeTable back_edges(unoptimized, &no_gc);
   for (uint32_t i = 0; i < back_edges.length(); i++) {
@@ -1631,8 +1632,8 @@ void BackEdgeTable::Patch(Isolate* isolate, Code* unoptimized) {
     }
   }
 
-  unoptimized->set_back_edges_patched_for_osr(true);
-  ASSERT(Verify(isolate, unoptimized, loop_nesting_level));
+  unoptimized->set_allow_osr_at_loop_nesting_level(loop_nesting_level);
+  ASSERT(Verify(isolate, unoptimized));
 }
 
 
@@ -1641,7 +1642,6 @@ void BackEdgeTable::Revert(Isolate* isolate, Code* unoptimized) {
   Code* patch = isolate->builtins()->builtin(Builtins::kInterruptCheck);
 
   // Iterate over the back edge table and revert the patched interrupt calls.
-  ASSERT(unoptimized->back_edges_patched_for_osr());
   int loop_nesting_level = unoptimized->allow_osr_at_loop_nesting_level();
 
   BackEdgeTable back_edges(unoptimized, &no_gc);
@@ -1654,10 +1654,9 @@ void BackEdgeTable::Revert(Isolate* isolate, Code* unoptimized) {
     }
   }
 
-  unoptimized->set_back_edges_patched_for_osr(false);
   unoptimized->set_allow_osr_at_loop_nesting_level(0);
   // Assert that none of the back edges are patched anymore.
-  ASSERT(Verify(isolate, unoptimized, -1));
+  ASSERT(Verify(isolate, unoptimized));
 }
 
 
@@ -1683,10 +1682,9 @@ void BackEdgeTable::RemoveStackCheck(Handle<Code> code, uint32_t pc_offset) {
 
 
 #ifdef DEBUG
-bool BackEdgeTable::Verify(Isolate* isolate,
-                           Code* unoptimized,
-                           int loop_nesting_level) {
+bool BackEdgeTable::Verify(Isolate* isolate, Code* unoptimized) {
   DisallowHeapAllocation no_gc;
+  int loop_nesting_level = unoptimized->allow_osr_at_loop_nesting_level();
   BackEdgeTable back_edges(unoptimized, &no_gc);
   for (uint32_t i = 0; i < back_edges.length(); i++) {
     uint32_t loop_depth = back_edges.loop_depth(i);

src/full-codegen.h

@@ -890,10 +890,8 @@ class BackEdgeTable {
     OSR_AFTER_STACK_CHECK
   };
 
-  // Patch all interrupts with allowed loop depth in the unoptimized code to
-  // unconditionally call replacement_code.
-  static void Patch(Isolate* isolate,
-                    Code* unoptimized_code);
+  // Increase allowed loop nesting level by one and patch those matching loops.
+  static void Patch(Isolate* isolate, Code* unoptimized_code);
 
   // Patch the back edge to the target state, provided the correct callee.
   static void PatchAt(Code* unoptimized_code,
@@ -919,9 +917,7 @@ class BackEdgeTable {
 
 #ifdef DEBUG
   // Verify that all back edges of a certain loop depth are patched.
-  static bool Verify(Isolate* isolate,
-                     Code* unoptimized_code,
-                     int loop_nesting_level);
+  static bool Verify(Isolate* isolate, Code* unoptimized_code);
 #endif  // DEBUG
 
  private:

src/globals.h

@@ -168,6 +168,8 @@ const size_t kMaximalCodeRangeSize = 0 * MB;
 #endif
 #endif
 
+STATIC_ASSERT(kPointerSize == (1 << kPointerSizeLog2));
+
 const int kBitsPerByte = 8;
 const int kBitsPerByteLog2 = 3;
 const int kBitsPerPointer = kPointerSize * kBitsPerByte;

src/objects-inl.h

@@ -4651,14 +4651,17 @@ void Code::set_compiled_optimizable(bool value) {
 
 int Code::allow_osr_at_loop_nesting_level() {
   ASSERT_EQ(FUNCTION, kind());
-  return READ_BYTE_FIELD(this, kAllowOSRAtLoopNestingLevelOffset);
+  int fields = READ_UINT32_FIELD(this, kKindSpecificFlags2Offset);
+  return AllowOSRAtLoopNestingLevelField::decode(fields);
 }
 
 
 void Code::set_allow_osr_at_loop_nesting_level(int level) {
   ASSERT_EQ(FUNCTION, kind());
   ASSERT(level >= 0 && level <= kMaxLoopNestingMarker);
-  WRITE_BYTE_FIELD(this, kAllowOSRAtLoopNestingLevelOffset, level);
+  int previous = READ_UINT32_FIELD(this, kKindSpecificFlags2Offset);
+  int updated = AllowOSRAtLoopNestingLevelField::update(previous, level);
+  WRITE_UINT32_FIELD(this, kKindSpecificFlags2Offset, updated);
 }
 
 
@@ -4711,13 +4714,14 @@ void Code::set_safepoint_table_offset(unsigned offset) {
 unsigned Code::back_edge_table_offset() {
   ASSERT_EQ(FUNCTION, kind());
   return BackEdgeTableOffsetField::decode(
-      READ_UINT32_FIELD(this, kKindSpecificFlags2Offset));
+      READ_UINT32_FIELD(this, kKindSpecificFlags2Offset)) << kPointerSizeLog2;
 }
 
 
 void Code::set_back_edge_table_offset(unsigned offset) {
   ASSERT_EQ(FUNCTION, kind());
-  ASSERT(IsAligned(offset, static_cast<unsigned>(kIntSize)));
+  ASSERT(IsAligned(offset, static_cast<unsigned>(kPointerSize)));
+  offset = offset >> kPointerSizeLog2;
   int previous = READ_UINT32_FIELD(this, kKindSpecificFlags2Offset);
   int updated = BackEdgeTableOffsetField::update(previous, offset);
   WRITE_UINT32_FIELD(this, kKindSpecificFlags2Offset, updated);
@@ -4726,20 +4730,10 @@ void Code::set_back_edge_table_offset(unsigned offset) {
 
 bool Code::back_edges_patched_for_osr() {
   ASSERT_EQ(FUNCTION, kind());
-  return BackEdgesPatchedForOSRField::decode(
-      READ_UINT32_FIELD(this, kKindSpecificFlags2Offset));
-}
-
-
-void Code::set_back_edges_patched_for_osr(bool value) {
-  ASSERT_EQ(FUNCTION, kind());
-  int previous = READ_UINT32_FIELD(this, kKindSpecificFlags2Offset);
-  int updated = BackEdgesPatchedForOSRField::update(previous, value);
-  WRITE_UINT32_FIELD(this, kKindSpecificFlags2Offset, updated);
+  return allow_osr_at_loop_nesting_level() > 0;
 }
 
 
-
 byte Code::to_boolean_state() {
   return extra_ic_state();
 }

src/objects.h

@@ -5569,7 +5569,6 @@ class Code: public HeapObject {
   inline void set_back_edge_table_offset(unsigned offset);
 
   inline bool back_edges_patched_for_osr();
-  inline void set_back_edges_patched_for_osr(bool value);
 
   // [to_boolean_foo]: For kind TO_BOOLEAN_IC tells what state the stub is in.
   inline byte to_boolean_state();
@@ -5814,8 +5813,7 @@ class Code: public HeapObject {
   class FullCodeFlagsHasDebugBreakSlotsField: public BitField<bool, 1, 1> {};
   class FullCodeFlagsIsCompiledOptimizable: public BitField<bool, 2, 1> {};
 
-  static const int kAllowOSRAtLoopNestingLevelOffset = kFullCodeFlags + 1;
-  static const int kProfilerTicksOffset = kAllowOSRAtLoopNestingLevelOffset + 1;
+  static const int kProfilerTicksOffset = kFullCodeFlags + 1;
 
   // Flags layout.  BitField<type, shift, size>.
   class ICStateField: public BitField<InlineCacheState, 0, 3> {};
@@ -5886,9 +5884,10 @@ class Code: public HeapObject {
 
   // KindSpecificFlags2 layout (FUNCTION)
   class BackEdgeTableOffsetField: public BitField<int,
-      kIsCrankshaftedBit + 1, 29> {};  // NOLINT
-  class BackEdgesPatchedForOSRField: public BitField<bool,
-      kIsCrankshaftedBit + 1 + 29, 1> {};  // NOLINT
+      kIsCrankshaftedBit + 1, 27> {};  // NOLINT
+  class AllowOSRAtLoopNestingLevelField: public BitField<int,
+      kIsCrankshaftedBit + 1 + 27, 4> {};  // NOLINT
+  STATIC_ASSERT(AllowOSRAtLoopNestingLevelField::kMax >= kMaxLoopNestingMarker);
 
   static const int kArgumentsBits = 16;
   static const int kMaxArguments = (1 << kArgumentsBits) - 1;

src/runtime-profiler.cc

@@ -110,7 +110,9 @@ void RuntimeProfiler::Optimize(JSFunction* function, const char* reason) {
 }
 
 
-void RuntimeProfiler::AttemptOnStackReplacement(JSFunction* function) {
+void RuntimeProfiler::AttemptOnStackReplacement(JSFunction* function,
+                                                int loop_nesting_levels) {
+  SharedFunctionInfo* shared = function->shared();
   // See AlwaysFullCompiler (in compiler.cc) comment on why we need
   // Debug::has_break_points().
   if (!FLAG_use_osr ||
@@ -119,7 +121,6 @@ void RuntimeProfiler::AttemptOnStackReplacement(JSFunction* function) {
     return;
   }
 
-  SharedFunctionInfo* shared = function->shared();
   // If the code is not optimizable, don't try OSR.
   if (!shared->code()->optimizable()) return;
 
@@ -137,7 +138,9 @@ void RuntimeProfiler::AttemptOnStackReplacement(JSFunction* function) {
     PrintF("]\n");
   }
 
-  BackEdgeTable::Patch(isolate_, shared->code());
+  for (int i = 0; i < loop_nesting_levels; i++) {
+    BackEdgeTable::Patch(isolate_, shared->code());
+  }
 }
 
 
@@ -175,14 +178,8 @@ void RuntimeProfiler::OptimizeNow() {
     if (shared_code->kind() != Code::FUNCTION) continue;
     if (function->IsInOptimizationQueue()) continue;
 
-    if (FLAG_always_osr &&
-        shared_code->allow_osr_at_loop_nesting_level() == 0) {
-      // Testing mode: always try an OSR compile for every function.
-      for (int i = 0; i < Code::kMaxLoopNestingMarker; i++) {
-        // TODO(titzer): fix AttemptOnStackReplacement to avoid this dumb loop.
-        shared_code->set_allow_osr_at_loop_nesting_level(i);
-        AttemptOnStackReplacement(function);
-      }
+    if (FLAG_always_osr) {
+      AttemptOnStackReplacement(function, Code::kMaxLoopNestingMarker);
       // Fall through and do a normal optimized compile as well.
     } else if (!frame->is_optimized() &&
         (function->IsMarkedForOptimization() ||
@@ -196,12 +193,7 @@ void RuntimeProfiler::OptimizeNow() {
       if (shared_code->CodeSize() > allowance) {
         if (ticks < 255) shared_code->set_profiler_ticks(ticks + 1);
       } else {
-        int nesting = shared_code->allow_osr_at_loop_nesting_level();
-        if (nesting < Code::kMaxLoopNestingMarker) {
-          int new_nesting = nesting + 1;
-          shared_code->set_allow_osr_at_loop_nesting_level(new_nesting);
-          AttemptOnStackReplacement(function);
-        }
+        AttemptOnStackReplacement(function);
       }
       continue;
     }

src/runtime-profiler.h

@@ -23,7 +23,7 @@ class RuntimeProfiler {
 
   void NotifyICChanged() { any_ic_changed_ = true; }
 
-  void AttemptOnStackReplacement(JSFunction* function);
+  void AttemptOnStackReplacement(JSFunction* function, int nesting_levels = 1);
 
  private:
   void Optimize(JSFunction* function, const char* reason);

src/runtime.cc

@@ -8530,16 +8530,11 @@ RUNTIME_FUNCTION(Runtime_OptimizeFunctionOnNextCall) {
   if (args.length() == 2 &&
       unoptimized->kind() == Code::FUNCTION) {
     CONVERT_ARG_HANDLE_CHECKED(String, type, 1);
-    if (type->IsOneByteEqualTo(STATIC_ASCII_VECTOR("osr"))) {
+    if (type->IsOneByteEqualTo(STATIC_ASCII_VECTOR("osr")) && FLAG_use_osr) {
       // Start patching from the currently patched loop nesting level.
-      int current_level = unoptimized->allow_osr_at_loop_nesting_level();
-      ASSERT(BackEdgeTable::Verify(isolate, unoptimized, current_level));
-      if (FLAG_use_osr) {
-        for (int i = current_level + 1; i <= Code::kMaxLoopNestingMarker; i++) {
-          unoptimized->set_allow_osr_at_loop_nesting_level(i);
-          isolate->runtime_profiler()->AttemptOnStackReplacement(*function);
-        }
-      }
+      ASSERT(BackEdgeTable::Verify(isolate, unoptimized));
+      isolate->runtime_profiler()->AttemptOnStackReplacement(
+          *function, Code::kMaxLoopNestingMarker);
     } else if (type->IsOneByteEqualTo(STATIC_ASCII_VECTOR("concurrent")) &&
                isolate->concurrent_recompilation_enabled()) {
       function->MarkForConcurrentOptimization();

test/mjsunit/regress/regress-crbug-387599.js

+// Copyright 2014 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.
+
+// Flags: --allow-natives-syntax --expose-debug-as debug
+
+Debug = debug.Debug;
+Debug.setListener(function() {});
+
+function f() {
+  for (var i = 0; i < 100; i++) {
+    %OptimizeFunctionOnNextCall(f, "osr");
+  }
+}
+
+Debug.setBreakPoint(f, 0, 0);
+f();
+f();
+Debug.setListener(null);