VM: Refactor allocation stats code and remove duplicate code.

runtime/vm/assembler_arm.cc

Index: runtime/vm/assembler_arm.cc
diff --git a/runtime/vm/assembler_arm.cc b/runtime/vm/assembler_arm.cc
index a354940d55c75da15cb049508cd3adb41a0ee217..f42f0759597ef669df54d65893879557c2c0b2df 100644
--- a/runtime/vm/assembler_arm.cc
+++ b/runtime/vm/assembler_arm.cc
@@ -3345,21 +3345,26 @@ void Assembler::LeaveStubFrame() {
 
 
 void Assembler::LoadAllocationStatsAddress(Register dest,
-                                           intptr_t cid) {
+                                           intptr_t cid,
+                                           bool inline_isolate) {
   ASSERT(dest != kNoRegister);
   ASSERT(dest != TMP);
   ASSERT(cid > 0);
-  Isolate* isolate = Isolate::Current();
-  ClassTable* class_table = isolate->class_table();
-  if (cid < kNumPredefinedCids) {
-    const uword class_heap_stats_table_address =
-        class_table->PredefinedClassHeapStatsTableAddress();
-    const uword class_offset = cid * sizeof(ClassHeapStats);  // NOLINT
-    LoadImmediate(dest, class_heap_stats_table_address + class_offset);
+  ClassTable* class_table = Isolate::Current()->class_table();
+  ClassHeapStats** table_ptr = class_table->TableAddressFor(cid);
+  const intptr_t class_offset = ClassTable::ClassOffsetFor(cid);
+  if (cid < kNumPredefinedCids && inline_isolate) {
+    LoadImmediate(dest, reinterpret_cast<uword>(*table_ptr) + class_offset);
   } else {
-    const uword class_offset = cid * sizeof(ClassHeapStats);  // NOLINT
-    LoadImmediate(dest, class_table->ClassStatsTableAddress());
-    ldr(dest, Address(dest, 0));
+    if (inline_isolate) {
+      LoadImmediate(dest, reinterpret_cast<uword>(table_ptr));
+      ldr(dest, Address(dest, 0));
+    } else {
+      LoadIsolate(dest);

[koda, 2015/07/16 15:45:18]

In this branch, one must not use "class_table", nor "table_ptr", so it would be
more robust if those locals were not even visible here.

In general, how fast/obviously will we fail if someone by mistake inlines
isolate-specific things during precompilation?

I think we should consider funneling these "reinterpret_cast" through some
interface that can assert that we're not precompiling.

[Florian Schneider, 2015/07/17 07:40:40]

Ok, I'll try to rearrange the code accordingly by checking

if (inline_isolate) first.


Often you just get a segfault. We have to check all places where we do something
like Immediate(reinterpret_cast<uword|int32_t|int64_t>some_ptr)

+      intptr_t table_offset =
+          Isolate::class_table_offset() + ClassTable::TableOffsetFor(cid);
+      ldr(dest, Address(dest, table_offset));
+    }
     AddImmediate(dest, class_offset);
   }
 }
@@ -3370,8 +3375,7 @@ void Assembler::MaybeTraceAllocation(intptr_t cid,
                                      Label* trace) {
   LoadAllocationStatsAddress(temp_reg, cid);
   const uword state_offset = ClassHeapStats::state_offset();
-  const Address& state_address = Address(temp_reg, state_offset);
-  ldr(temp_reg, state_address);
+  ldr(temp_reg, Address(temp_reg, state_offset));
   tst(temp_reg, Operand(ClassHeapStats::TraceAllocationMask()));
   b(trace, NE);
 }
@@ -3395,11 +3399,9 @@ void Assembler::IncrementAllocationStats(Register stats_addr_reg,
 
 void Assembler::IncrementAllocationStatsWithSize(Register stats_addr_reg,
                                                  Register size_reg,
-                                                 intptr_t cid,
                                                  Heap::Space space) {
   ASSERT(stats_addr_reg != kNoRegister);
   ASSERT(stats_addr_reg != TMP);
-  ASSERT(cid > 0);
   const uword count_field_offset = (space == Heap::kNew) ?
     ClassHeapStats::allocated_since_gc_new_space_offset() :
     ClassHeapStats::allocated_since_gc_old_space_offset();
@@ -3515,7 +3517,7 @@ void Assembler::TryAllocateArray(intptr_t cid,
     str(temp1, FieldAddress(instance, Array::tags_offset()));  // Store tags.
 
     LoadImmediate(temp1, instance_size);
-    IncrementAllocationStatsWithSize(temp2, temp1, cid, space);
+    IncrementAllocationStatsWithSize(temp2, temp1, space);
   } else {
     b(failure);
   }