Fixing dead code in empty array init.

src/mips/builtins-mips.cc

Index: src/mips/builtins-mips.cc
diff --git a/src/mips/builtins-mips.cc b/src/mips/builtins-mips.cc
index 1687abe8803ec351e8e285e038013eabb2c69be6..bc373e45cb0df65e41ba4a1d496d3e07d9cb6128 100644
--- a/src/mips/builtins-mips.cc
+++ b/src/mips/builtins-mips.cc
@@ -106,7 +106,10 @@ static void AllocateEmptyJSArray(MacroAssembler* masm,
 
   // Allocate the JSArray object together with space for a fixed array with the
   // requested elements.
-  int size = JSArray::kSize + FixedArray::SizeFor(initial_capacity);
+  int size = JSArray::kSize;
+  if (initial_capacity > 0) {
+    size += FixedArray::SizeFor(initial_capacity);
+  }
   __ AllocateInNewSpace(size,
                         result,
                         scratch2,
@@ -125,6 +128,11 @@ static void AllocateEmptyJSArray(MacroAssembler* masm,
   __ mov(scratch3,  zero_reg);
   __ sw(scratch3, FieldMemOperand(result, JSArray::kLengthOffset));
 
+  if (initial_capacity == 0) {
+    __ sw(scratch1, FieldMemOperand(result, JSArray::kElementsOffset));
+    return;
+  }
+
   // Calculate the location of the elements array and set elements array member
   // of the JSArray.
   // result: JSObject
@@ -150,7 +158,6 @@ static void AllocateEmptyJSArray(MacroAssembler* masm,
   __ Addu(scratch1, scratch1, kPointerSize);
 
   // Fill the FixedArray with the hole value. Inline the code if short.
-  if (initial_capacity == 0) return;
   ASSERT_EQ(2 * kPointerSize, FixedArray::kHeaderSize);

[Kevin Millikin (Chromium), 2011/10/27 10:35:54]

Also here.

   __ LoadRoot(scratch3, Heap::kTheHoleValueRootIndex);
   static const int kLoopUnfoldLimit = 4;