Optimize test for pointer being in a partition on 32-bit.

Source/wtf/PageAllocator.cpp

Index: Source/wtf/PageAllocator.cpp
diff --git a/Source/wtf/PageAllocator.cpp b/Source/wtf/PageAllocator.cpp
index 35b24df67c7c92d33928df89a8717f34c26301fd..7b34d76f3e5bdf837fba65590b3645b64f5ab001 100644
--- a/Source/wtf/PageAllocator.cpp
+++ b/Source/wtf/PageAllocator.cpp
@@ -31,8 +31,6 @@
 #include "config.h"
 #include "wtf/PageAllocator.h"
 
-#include "wtf/Assertions.h"
-#include "wtf/CPU.h"
 #include "wtf/CryptographicallyRandomNumber.h"
 
 #if OS(POSIX)
@@ -97,6 +95,8 @@ void* allocSuperPages(void* addr, size_t len)
         ret = VirtualAlloc(0, len, MEM_RESERVE | MEM_COMMIT, PAGE_READWRITE);
     RELEASE_ASSERT(ret);
 #endif // OS(POSIX)
+
+    SuperPageBitmap::registerSuperPage(ret);
     return ret;
 }
 
@@ -111,6 +111,8 @@ void freeSuperPages(void* addr, size_t len)
     BOOL ret = VirtualFree(addr, 0, MEM_RELEASE);
     ASSERT(ret);
 #endif
+
+    SuperPageBitmap::unregisterSuperPage(addr);
 }
 
 void setSystemPagesInaccessible(void* addr, size_t len)
@@ -163,5 +165,31 @@ char* getRandomSuperPageBase()
     return reinterpret_cast<char*>(random);
 }
 
+#if CPU(32BIT)
+unsigned char SuperPageBitmap::s_bitmap[1 << (32 - kSuperPageShift - 3)];
+
+void SuperPageBitmap::registerSuperPage(void* ptr)
+{
+    ASSERT(!isPointerInSuperPage(ptr));
+    uintptr_t raw = reinterpret_cast<uintptr_t>(ptr);
+    raw >>= kSuperPageShift;
+    size_t idx = raw >> 3;

[ojan, 2013/10/03 00:44:09]

Nit: Here an elsewhere, I'm not sure what "idx" stands for. Is this supposed to
be "index"? Blink code prefers to avoid abbreviations in general.

+    size_t bit = raw & 7;
+    ASSERT(idx < sizeof(s_bitmap));
+    s_bitmap[idx] |= (1 << bit);
+}
+
+void SuperPageBitmap::unregisterSuperPage(void* ptr)
+{
+    ASSERT(isPointerInSuperPage(ptr));
+    uintptr_t raw = reinterpret_cast<uintptr_t>(ptr);
+    raw >>= kSuperPageShift;
+    size_t idx = raw >> 3;
+    size_t bit = raw & 7;
+    ASSERT(idx < sizeof(s_bitmap));
+    s_bitmap[idx] &= ~(1 << bit);
+}
+#endif
+
 } // namespace WTF