Postpone initialization of StructureAlignedMemoryAllocator.

https://bugs.webkit.org/show_bug.cgi?id=263380

Reviewed by Keith Miller.

StructureAlignedMemoryAllocator reserves a large amount of pages at startup
even on UIProcess and NetworkProcess because the initialization is called from
JSC::initialize().

In this patch, we postpone the initialization of StructureAlignedMemoryAllocator
until the first time it is used. Because permanentlyFreeze() will be called
at the end of construction of VM, it is safe to postpone the initialization.

* Source/JavaScriptCore/heap/StructureAlignedMemoryAllocator.cpp:
(JSC::StructureAlignedMemoryAllocator::tryMallocBlock):
* Source/JavaScriptCore/runtime/InitializeThreading.cpp:
(JSC::initialize):

Canonical link: https://commits.webkit.org/269633@main

Source/JavaScriptCore/heap/StructureAlignedMemoryAllocator.cpp

@@ -164,6 +164,10 @@ void StructureAlignedMemoryAllocator::initializeStructureAddressSpace()
 
 void* StructureAlignedMemoryAllocator::tryMallocBlock()
 {
+    static std::once_flag s_onceFlag;
+    std::call_once(s_onceFlag, [] {
+        initializeStructureAddressSpace();
+    });
     return s_structureMemoryManager->tryMallocStructureBlock();
 }
 

Source/JavaScriptCore/runtime/InitializeThreading.cpp

@@ -38,7 +38,6 @@
 #include "LLIntData.h"
 #include "NativeCalleeRegistry.h"
 #include "Options.h"
-#include "StructureAlignedMemoryAllocator.h"
 #include "SuperSampler.h"
 #include "VMTraps.h"
 #include "WasmCapabilities.h"
@@ -92,7 +91,6 @@ void initialize()
                 isARM64E_FPAC(); // Call this to initialize g_jscConfig.canUseFPAC.
 #endif
             }
-            StructureAlignedMemoryAllocator::initializeStructureAddressSpace();
         }
         Options::finalize();