Index: mozilla/js/src/gc/Heap.h

===================================================================

--- mozilla.orig/js/src/gc/Heap.h

+++ mozilla/js/src/gc/Heap.h

@@ -110,19 +110,22 @@ struct Cell

  */

 #if defined(SOLARIS) && (defined(__sparc) || defined(__sparcv9))

 const size_t PageShift = 13;

+const size_t ArenaShift = PageShift;

+#elif defined(__powerpc__)

+const size_t PageShift = 16;

+const size_t ArenaShift = 12;

 #else

 const size_t PageShift = 12;

+const size_t ArenaShift = PageShift;

 #endif

 const size_t PageSize = size_t(1) << PageShift;

+const size_t ArenaSize = size_t(1) << ArenaShift;

+const size_t ArenaMask = ArenaSize - 1;

 const size_t ChunkShift = 20;

 const size_t ChunkSize = size_t(1) << ChunkShift;

 const size_t ChunkMask = ChunkSize - 1;

-const size_t ArenaShift = PageShift;

-const size_t ArenaSize = PageSize;

-const size_t ArenaMask = ArenaSize - 1;

-

 /*

  * This is the maximum number of arenas we allow in the FreeCommitted state

  * before we trigger a GC_SHRINK to release free arenas to the OS.

Index: mozilla/js/src/gc/Memory.cpp

===================================================================

--- mozilla.orig/js/src/gc/Memory.cpp

+++ mozilla/js/src/gc/Memory.cpp

@@ -15,6 +15,15 @@

 namespace js {

 namespace gc {

+/* Unused memory decommiting requires the arena size match the page size. */

+extern const size_t PageSize;

+extern const size_t ArenaSize;

+static bool

+DecommitEnabled()

+{

+    return PageSize == ArenaSize;

+}

+

 #if defined(XP_WIN)

 #include "jswin.h"

 #include <psapi.h>

@@ -83,6 +92,9 @@ UnmapPages(void *p, size_t size)

 bool

 MarkPagesUnused(void *p, size_t size)

 {

+    if (!DecommitEnabled())

+        return false;

+

     JS_ASSERT(uintptr_t(p) % PageSize == 0);

     LPVOID p2 = VirtualAlloc(p, size, MEM_RESET, PAGE_READWRITE);

     return p2 == p;

@@ -352,6 +364,9 @@ UnmapPages(void *p, size_t size)

 bool

 MarkPagesUnused(void *p, size_t size)

 {

+    if (!DecommitEnabled())

+        return false;

+

     JS_ASSERT(uintptr_t(p) % PageSize == 0);

     int result = madvise(p, size, MADV_DONTNEED);

     return result != -1;