Allocate all executable code within a 2 GB code range.

test/cctest/test-alloc.cc

Index: test/cctest/test-alloc.cc
===================================================================
--- test/cctest/test-alloc.cc	(revision 3003)
+++ test/cctest/test-alloc.cc	(working copy)
@@ -144,3 +144,65 @@
   CHECK_EQ(42, result->Int32Value());
   env->Exit();
 }
+
+
+// CodeRange test.
+// Tests memory management in a CodeRange by allocating and freeing blocks,
+// using a pseudorandom generator to choose block sizes geometrically
+// distributed between 2 * Page::kPageSize and 2^5 + 1 * Page::kPageSize.
+// Ensure that the freed chunks are collected and reused by allocating (in
+// total) more than the size of the CodeRange.
+
+// This pseudorandom generator does not need to be particularly good.
+// Use the lower half of the V8::Random() generator.
+unsigned int Pseudorandom() {
+  static uint32_t lo = 2345;
+  lo = 18273 * (lo & 0xFFFF) + (lo >> 16);  // Provably not 0.
+  return lo & 0xFFFF;
+}
+
+
+// Plain old data class.  Represents a block of allocated memory.
+class Block {
+ public:
+  Block(void* base_arg, int size_arg)
+      : base(base_arg), size(size_arg) {}
+
+  void *base;
+  int size;
+};
+
+
+TEST(CodeRange) {
+  const int code_range_size = 16*MB;
+  CodeRange::Setup(code_range_size);
+  int current_allocated = 0;
+  int total_allocated = 0;
+  List<Block> blocks(1000);
+
+  while (total_allocated < 5 * code_range_size) {
+    if (current_allocated < code_range_size / 10) {
+      // Allocate a block.
+      // Geometrically distributed sizes, greater than Page::kPageSize.
+      size_t requested = (Page::kPageSize << (Pseudorandom() % 6)) +
+           Pseudorandom() % 5000 + 1;
+      size_t allocated = 0;
+      void* base = CodeRange::AllocateRawMemory(requested, &allocated);
+      blocks.Add(Block(base, allocated));
+      current_allocated += allocated;
+      total_allocated += allocated;
+    } else {
+      // Free a block.
+      int index = Pseudorandom() % blocks.length();
+      CodeRange::FreeRawMemory(blocks[index].base, blocks[index].size);
+      current_allocated -= blocks[index].size;
+      if (index < blocks.length() - 1) {
+        blocks[index] = blocks.RemoveLast();
+      } else {
+        blocks.RemoveLast();
+      }
+    }
+  }
+
+  CodeRange::TearDown();
+}