Faster filling of arrays of holes.

Review URL: http://codereview.chromium.org/661105

git-svn-id: http://v8.googlecode.com/svn/branches/bleeding_edge@3977 ce2b1a6d-e550-0410-aec6-3dcde31c8c00

diff --git a/src/heap.cc b/src/heap.cc
index 524e8e23d4c0c427e5fb02cc8a00bf69b2331d17..157578da247a9537180a65266b72bc1e2df19950 100644 (file)
--- a/src/heap.cc
+++ b/src/heap.cc
@@ -2994,11 +2994,10 @@ Object* Heap::AllocateFixedArrayWithHoles(int length) {
     FixedArray* array = FixedArray::cast(result);
     array->set_length(length);
     // Initialize body.
-    Object* value = the_hole_value();
-    for (int index = 0; index < length; index++)  {
-      ASSERT(!Heap::InNewSpace(value));  // value = the hole
-      array->set(index, value, SKIP_WRITE_BARRIER);
-    }
+    ASSERT(!Heap::InNewSpace(the_hole_value()));
+    MemsetPointer(HeapObject::RawField(array, FixedArray::kHeaderSize),
+                  the_hole_value(),
+                  length);
   }
   return result;
 }

diff --git a/src/utils.h b/src/utils.h
index 2cad4c12e4a8f93ee46cd4d2214b8583d8f09dbb..deab09fb1193215b6d4dd06f910d2da3256a24ba 100644 (file)
--- a/src/utils.h
+++ b/src/utils.h
@@ -572,6 +572,30 @@ static inline int CompareChars(const lchar* lhs, const rchar* rhs, int chars) {
 }
 
 
+template <typename T>
+static inline void MemsetPointer(T** dest, T* value, int counter) {
+#if defined(V8_HOST_ARCH_IA32)
+#define STOS "stosl"
+#elif defined(V8_HOST_ARCH_X64)
+#define STOS "stosq"
+#endif
+
+#if defined(__GNUC__) && defined(STOS)
+  asm("cld;"
+      "rep ; " STOS
+      : /* no output */
+      : "c" (counter), "a" (value), "D" (dest)
+      : /* no clobbered list as all inputs are considered clobbered */);
+#else
+  for (int i = 0; i < counter; i++) {
+    dest[i] = value;
+  }
+#endif
+
+#undef STOS
+}
+
+
 // Calculate 10^exponent.
 int TenToThe(int exponent);