Fix improved LoadICs for dictionaries with callbacks.

src/arm/stub-cache-arm.cc

Index: src/arm/stub-cache-arm.cc
diff --git a/src/arm/stub-cache-arm.cc b/src/arm/stub-cache-arm.cc
index 37a3c4f42df25f37f9600b789bed5c1e8a083866..d760d6d8e2cda6d69eae874b6ad25c67eb9a39f4 100644
--- a/src/arm/stub-cache-arm.cc
+++ b/src/arm/stub-cache-arm.cc
@@ -1238,30 +1238,44 @@ void StubCompiler::GenerateDictionaryLoadCallback(Register receiver,
                                                   Handle<AccessorInfo> callback,
                                                   Handle<String> name,
                                                   Label* miss) {
+  ASSERT(!receiver.is(scratch2));
+  ASSERT(!receiver.is(scratch3));
   Register dictionary = scratch1;
-  Register index = scratch2;
+  bool must_preserve_dictionary_reg = receiver.is(dictionary);
+
+  // Load the properties dictionary.
+  if (must_preserve_dictionary_reg) {
+    __ push(dictionary);

[Erik Corry, 2012/08/14 11:03:33]

This is slow on ARM and unnecessary when there are 16 registers.

[Michael Starzinger, 2012/08/14 11:44:05]

Done.

+  }
   __ ldr(dictionary, FieldMemOperand(receiver, JSObject::kPropertiesOffset));
 
   // Probe the dictionary.
-  Label probe_done;
+  Label probe_done, pop_and_miss;
   StringDictionaryLookupStub::GeneratePositiveLookup(masm(),
-                                                     miss,
+                                                     &pop_and_miss,
                                                      &probe_done,
                                                      dictionary,
                                                      name_reg,
-                                                     index,  // Set if we hit.
+                                                     scratch2,
                                                      scratch3);
+  __ bind(&pop_and_miss);
+  if (must_preserve_dictionary_reg) {
+    __ pop(dictionary);
+  }
+  __ jmp(miss);
   __ bind(&probe_done);
+  if (must_preserve_dictionary_reg) {
+    __ pop(dictionary);
+  }
 
-  // If probing finds an entry in the dictionary, check that the value is the
-  // callback.
-  const int kElementsStartOffset =
-      StringDictionary::kHeaderSize +
+  // If probing finds an entry in the dictionary, scratch3 contains the
+  // pointer into the dictionary. Check that the value is the callback.
+  Register pointer = scratch3;
+  const int kElementsStartOffset = StringDictionary::kHeaderSize +
       StringDictionary::kElementsStartIndex * kPointerSize;
   const int kValueOffset = kElementsStartOffset + kPointerSize;
-  __ add(scratch1, dictionary, Operand(kValueOffset - kHeapObjectTag));
-  __ ldr(scratch3, MemOperand(scratch1, index, LSL, kPointerSizeLog2));
-  __ cmp(scratch3, Operand(callback));
+  __ ldr(scratch2, FieldMemOperand(pointer, kValueOffset));
+  __ cmp(scratch2, Operand(callback));
   __ b(ne, miss);
 }
 
@@ -1285,7 +1299,7 @@ void StubCompiler::GenerateLoadCallback(Handle<JSObject> object,
 
   if (!holder->HasFastProperties() && !holder->IsJSGlobalObject()) {
     GenerateDictionaryLoadCallback(
-        receiver, name_reg, scratch1, scratch2, scratch3, callback, name, miss);
+        reg, name_reg, scratch1, scratch2, scratch3, callback, name, miss);
   }
 
   // Build AccessorInfo::args_ list on the stack and push property name below