Reviewed by Geoffrey Garen.

        Try to release unused executable memory when the FixedVMPool allocator is under pressure
        https://bugs.webkit.org/show_bug.cgi?id=61651

        Rather than crashing when full the FixedVMPool allocator now returns a null
        allocation.  We replace the code that used to CRASH() on null allocations
        with logic that asks the provided globalData to release any executable memory
        that it can.  Currently this just means throwing away all regexp code, but
        in future we'll try to be more aggressive.

        * assembler/ARMAssembler.cpp:
        (JSC::ARMAssembler::executableCopy):
        * assembler/ARMAssembler.h:
        * assembler/AssemblerBuffer.h:
        (JSC::AssemblerBuffer::executableCopy):
        * assembler/AssemblerBufferWithConstantPool.h:
        * assembler/LinkBuffer.h:
        (JSC::LinkBuffer::LinkBuffer):
        (JSC::LinkBuffer::linkCode):
        * assembler/MIPSAssembler.h:
        (JSC::MIPSAssembler::executableCopy):
        * assembler/SH4Assembler.h:
        (JSC::SH4Assembler::executableCopy):
        * assembler/X86Assembler.h:
        (JSC::X86Assembler::executableCopy):
        (JSC::X86Assembler::X86InstructionFormatter::executableCopy):
        * dfg/DFGJITCompiler.cpp:
        (JSC::DFG::JITCompiler::compileFunction):
        * jit/ExecutableAllocator.h:
        (JSC::ExecutablePool::create):
        (JSC::ExecutablePool::alloc):
        (JSC::ExecutableAllocator::ExecutableAllocator):
        (JSC::ExecutableAllocator::poolForSize):
        (JSC::ExecutablePool::ExecutablePool):
        (JSC::ExecutablePool::poolAllocate):
        * jit/ExecutableAllocatorFixedVMPool.cpp:
        (JSC::FixedVMPoolAllocator::alloc):
        * jit/JIT.cpp:
        (JSC::JIT::privateCompile):
        * jit/JITOpcodes.cpp:
        (JSC::JIT::privateCompileCTIMachineTrampolines):
        * jit/JITOpcodes32_64.cpp:
        (JSC::JIT::privateCompileCTIMachineTrampolines):
        (JSC::JIT::privateCompileCTINativeCall):
        * jit/JITPropertyAccess.cpp:
        (JSC::JIT::stringGetByValStubGenerator):
        (JSC::JIT::privateCompilePutByIdTransition):
        (JSC::JIT::privateCompilePatchGetArrayLength):
        (JSC::JIT::privateCompileGetByIdProto):
        (JSC::JIT::privateCompileGetByIdSelfList):
        (JSC::JIT::privateCompileGetByIdProtoList):
        (JSC::JIT::privateCompileGetByIdChainList):
        (JSC::JIT::privateCompileGetByIdChain):
        * jit/JITPropertyAccess32_64.cpp:
        (JSC::JIT::stringGetByValStubGenerator):
        (JSC::JIT::privateCompilePutByIdTransition):
        (JSC::JIT::privateCompilePatchGetArrayLength):
        (JSC::JIT::privateCompileGetByIdProto):
        (JSC::JIT::privateCompileGetByIdSelfList):
        (JSC::JIT::privateCompileGetByIdProtoList):
        (JSC::JIT::privateCompileGetByIdChainList):
        (JSC::JIT::privateCompileGetByIdChain):
        * jit/SpecializedThunkJIT.h:
        (JSC::SpecializedThunkJIT::finalize):
        * jit/ThunkGenerators.cpp:
        (JSC::charCodeAtThunkGenerator):
        (JSC::charAtThunkGenerator):
        (JSC::fromCharCodeThunkGenerator):
        (JSC::sqrtThunkGenerator):
        (JSC::powThunkGenerator):
        * runtime/JSGlobalData.cpp:
        (JSC::JSGlobalData::JSGlobalData):
        (JSC::JSGlobalData::releaseExecutableMemory):
        (JSC::releaseExecutableMemory):
        * runtime/JSGlobalData.h:
        * runtime/RegExpCache.cpp:
        (JSC::RegExpCache::invalidateCode):
        * runtime/RegExpCache.h:
        * yarr/YarrJIT.cpp:
        (JSC::Yarr::YarrGenerator::compile):

git-svn-id: http://svn.webkit.org/repository/webkit/trunk@87527 268f45cc-cd09-0410-ab3c-d52691b4dbfc