- Wire the stack frame iterator to use stack maps for traversing objects if there are stack maps in…

vm/object.cc

Index: vm/object.cc
===================================================================
--- vm/object.cc	(revision 6294)
+++ vm/object.cc	(working copy)
@@ -9,7 +9,6 @@
 #include "vm/bigint_operations.h"
 #include "vm/bootstrap.h"
 #include "vm/code_generator.h"
-#include "vm/code_index_table.h"
 #include "vm/code_patcher.h"
 #include "vm/compiler.h"
 #include "vm/compiler_stats.h"
@@ -26,6 +25,7 @@
 #include "vm/parser.h"
 #include "vm/runtime_entry.h"
 #include "vm/scopes.h"
+#include "vm/stack_frame.h"
 #include "vm/timer.h"
 #include "vm/unicode.h"
 
@@ -5566,26 +5566,6 @@
 }
 
 
-// Return the bit offset of the highest bit set.
-intptr_t Stackmap::Maximum() const {
-  intptr_t bound = SizeInBits();
-  for (intptr_t i = (bound - 1); i >= 0; i--) {
-    if (IsObject(i)) return i;
-  }
-  return kNoMaximum;
-}
-
-
-// Return the bit offset of the lowest bit set.
-intptr_t Stackmap::Minimum() const {
-  intptr_t bound = SizeInBits();
-  for (intptr_t i = 0; i < bound; i++) {
-    if (IsObject(i)) return i;
-  }
-  return kNoMinimum;
-}
-
-
 bool Stackmap::GetBit(intptr_t bit_offset) const {
   ASSERT(InRange(bit_offset));
   int byte_offset = bit_offset >> kBitsPerByteLog2;
@@ -5610,7 +5590,7 @@
 }
 
 
-RawStackmap* Stackmap::New(uword pc, const Code& code, BitmapBuilder* bmap) {
+RawStackmap* Stackmap::New(uword pc_offset, BitmapBuilder* bmap) {
   const Class& cls = Class::Handle(Object::stackmap_class());
   ASSERT(!cls.IsNull());
   ASSERT(bmap != NULL);
@@ -5625,12 +5605,13 @@
     result ^= raw;
     result.set_bitmap_size_in_bytes(size);
   }
-  result.set_pc(pc);
-  result.set_code(code);
+  result.SetPC(pc_offset);
   intptr_t bound = bmap->SizeInBits();
   for (intptr_t i = 0; i < bound; i++) {
     result.SetBit(i, bmap->Get(i));
   }
+  result.SetMinBitOffset(bmap->Minimum());
+  result.SetMaxBitOffset(bmap->Maximum());
   return result.raw();
 }
 
@@ -5642,27 +5623,18 @@
 }
 
 
-void Stackmap::set_pc(uword value) const {
-  raw_ptr()->pc_ = value;
-}
-
-
-void Stackmap::set_code(const Code& code) const {
-  StorePointer(&raw_ptr()->code_, code.raw());
-}
-
-
 const char* Stackmap::ToCString() const {
   if (IsNull()) {
     return "{null}";
   } else {
     intptr_t index = OS::SNPrint(NULL, 0, "0x%lx { ", PC());
-    intptr_t alloc_size = index + ((Maximum() + 1) * 2) + 2;  // "{ 1 0 .... }".
+    intptr_t alloc_size =
+        index + ((MaximumBitOffset() + 1) * 2) + 2;  // "{ 1 0 .... }".
     Isolate* isolate = Isolate::Current();
     char* chars = reinterpret_cast<char*>(
         isolate->current_zone()->Allocate(alloc_size));
     index = OS::SNPrint(chars, alloc_size, "0x%lx { ", PC());
-    for (intptr_t i = 0; i <= Maximum(); i++) {
+    for (intptr_t i = 0; i <= MaximumBitOffset(); i++) {
       index += OS::SNPrint((chars + index),
                            (alloc_size - index),
                            "%d ",
@@ -5995,6 +5967,38 @@
 }
 
 
+RawStackmap* Code::GetStackmap(uword pc, Array* maps, Stackmap* map) const {
+  // This code is used only during iterating frames during a GC and hence
+  // it should not in turn start a GC.
+  NoGCScope no_gc;
+  if (stackmaps() == Array::null()) {
+    // No stack maps are present in the code object which means this
+    // frame relies on tagged pointers.
+    return Stackmap::null();
+  }
+  // A stack map is present in the code object, use the stack map to visit
+  // frame slots which are marked as having objects.
+  RawStackmap* previous_map = Stackmap::null();
+  *maps = stackmaps();
+  *map = Stackmap::null();
+  for (intptr_t i = 0; i < maps->Length(); i++) {
+    *map ^= maps->At(i);
+    ASSERT(!map->IsNull());
+    if (map->PC() == pc) {
+      break;  // We found a stack map for this frame.
+    }
+    if (map->PC() > pc) {
+      // We have not found a stackmap corresponding to the PC of this frame,
+      // we will use the closest previous stack map.
+      *map = previous_map;
+      break;
+    }
+    previous_map = map->raw();
+  }
+  return map->raw();
+}
+
+
 RawContext* Context::New(intptr_t num_variables, Heap::Space space) {
   ASSERT(num_variables >= 0);
 
@@ -8879,17 +8883,16 @@
 
 void Stacktrace::SetupStacktrace(intptr_t index,
                                  const GrowableArray<uword>& frame_pcs) const {
-  ASSERT(Isolate::Current() != NULL);
-  CodeIndexTable* code_index_table = Isolate::Current()->code_index_table();
-  ASSERT(code_index_table != NULL);
-  Function& function = Function::Handle();
-  Code& code = Code::Handle();
-  Smi& pc_offset = Smi::Handle();
+  Isolate* isolate = Isolate::Current();
+  ASSERT(isolate != NULL);
+  Function& function = Function::Handle(isolate, Function::null());
+  Code& code = Code::Handle(isolate, Code::null());
+  Smi& pc_offset = Smi::Handle(isolate, Smi::New(0));
   const Array& function_array = Array::Handle(raw_ptr()->function_array_);
   const Array& code_array = Array::Handle(raw_ptr()->code_array_);
   const Array& pc_offset_array = Array::Handle(raw_ptr()->pc_offset_array_);
   for (intptr_t i = 0; i < frame_pcs.length(); i++) {
-    code = code_index_table->LookupCode(frame_pcs[i]);
+    code = StackFrame::LookupCode(isolate, frame_pcs[i]);
     ASSERT(!code.IsNull());
     function = code.function();
     function_array.SetAt((index + i), function);