Additional work to get array literal allocation tracking working, even with --always-opt

src/arm/lithium-codegen-arm.cc

Index: src/arm/lithium-codegen-arm.cc
diff --git a/src/arm/lithium-codegen-arm.cc b/src/arm/lithium-codegen-arm.cc
index 9a830733feaafb5307493e3943a6ec6d5d47f7a2..f3f663ab165517f2a30c70bc02a5b6304ec49304 100644
--- a/src/arm/lithium-codegen-arm.cc
+++ b/src/arm/lithium-codegen-arm.cc
@@ -5469,10 +5469,18 @@ void LCodeGen::DoArrayLiteral(LArrayLiteral* instr) {
   } else if (length > FastCloneShallowArrayStub::kMaximumClonedLength) {
     CallRuntime(Runtime::kCreateArrayLiteralShallow, 3, instr);
   } else {
-    FastCloneShallowArrayStub::Mode mode =
+    // TODO(mvstanton): I'm doing more work than necessary here by running
+    // CLONE_ANY_ELEMENTS instead of the more specific stub, but I'm doing it
+    // just because I want to track allocation info. Alternative approach: quick
+    // baking allocation tracking info into this field, instead just have it on
+    // all the time?

[danno, 2013/01/10 22:58:59]

Be careful (here and on other platforms). Originally when I wrote this code, I
only had the CLONE_ANY_ELEMENTS version. When it landed in Chromium, I tanked
performance in the page cycler performance bots and had to make sure that the
CLONE_ELEMENTS and CLONE_DOUBLE_ELEMENTS were used whenever possible. May it's
time to separate FastCloneShallowArrayStub::Mode and the flag to create site
info always into to fields, and generate 6 versions of the copy stub,
CLONE_DOUBLE, CLONE_ELEMENTS, CLONE_ANY in two versions, one with
AllocationInfo, one without.

[mvstanton, 2013/01/11 13:43:01]

Done.

+    FastCloneShallowArrayStub::Mode mode = FastCloneShallowArrayStub::
+        CLONE_ANY_ELEMENTS_WITH_ALLOCATION_SITE_INFO;
+    /*
         boilerplate_elements_kind == FAST_DOUBLE_ELEMENTS
             ? FastCloneShallowArrayStub::CLONE_DOUBLE_ELEMENTS
             : FastCloneShallowArrayStub::CLONE_ELEMENTS;
+    */
     FastCloneShallowArrayStub stub(mode, length);
     CallCode(stub.GetCode(), RelocInfo::CODE_TARGET, instr);
   }
@@ -5482,7 +5490,8 @@ void LCodeGen::DoArrayLiteral(LArrayLiteral* instr) {
 void LCodeGen::EmitDeepCopy(Handle<JSObject> object,
                             Register result,
                             Register source,
-                            int* offset) {
+                            int* offset,
+                            bool create_allocation_site_info) {
   ASSERT(!source.is(r2));
   ASSERT(!result.is(r2));
 
@@ -5496,8 +5505,14 @@ void LCodeGen::EmitDeepCopy(Handle<JSObject> object,
   int object_offset = *offset;
   int object_size = object->map()->instance_size();
   int elements_offset = *offset + object_size;
+  if (create_allocation_site_info) {
+    elements_offset += AllocationSiteInfo::kSize;
+  }
   int elements_size = has_elements ? elements->Size() : 0;
   *offset += object_size + elements_size;
+  if (create_allocation_site_info) {
+    *offset += AllocationSiteInfo::kSize;
+  }
 
   // Copy object header.
   ASSERT(object->properties()->length() == 0);
@@ -5531,6 +5546,14 @@ void LCodeGen::EmitDeepCopy(Handle<JSObject> object,
     }
   }
 
+  // Build Allocation Site Info if desired
+  if (create_allocation_site_info) {
+    __ mov(r2, Operand(Handle<Map>(isolate()->heap()->
+                                   allocation_site_info_map())));
+    __ str(r2, FieldMemOperand(result, object_size));
+    __ str(source, FieldMemOperand(result, object_size + kPointerSize));
+  }
+
   if (has_elements) {
     // Copy elements backing store header.
     __ LoadHeapObject(source, elements);
@@ -5617,7 +5640,8 @@ void LCodeGen::DoFastLiteral(LFastLiteral* instr) {
   __ bind(&allocated);
   int offset = 0;
   __ LoadHeapObject(r1, instr->hydrogen()->boilerplate());
-  EmitDeepCopy(instr->hydrogen()->boilerplate(), r0, r1, &offset);
+  EmitDeepCopy(instr->hydrogen()->boilerplate(), r0, r1, &offset,
+               instr->hydrogen()->create_allocation_site_info());
   ASSERT_EQ(size, offset);
 }