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52-502: V8 is a JavaScript and WebAssembly engine developed by Google for its Chrome browser . V8 is free and open-source software that is part of the Chromium project and also used separately in non-browser contexts, notably the Node.js runtime system . Google created V8 for its Chrome browser, and both were first released in 2008. The lead developer of V8 was Lars Bak , and it

104-409: A 32-bit to a 64-bit architecture is a fundamental alteration, as most operating systems must be extensively modified to take advantage of the new architecture, because that software has to manage the actual memory addressing hardware. Other software must also be ported to use the new abilities; older 32-bit software may be supported either by virtue of the 64-bit instruction set being a superset of

156-613: A virtual machine of a 16- or 32-bit operating system to run 16-bit applications or use one of the alternatives for NTVDM . Mac OS X 10.4 "Tiger" and Mac OS X 10.5 "Leopard" had only a 32-bit kernel, but they can run 64-bit user-mode code on 64-bit processors. Mac OS X 10.6 "Snow Leopard" had both 32- and 64-bit kernels, and, on most Macs, used the 32-bit kernel even on 64-bit processors. This allowed those Macs to support 64-bit processes while still supporting 32-bit device drivers; although not 64-bit drivers and performance advantages that can come with them. Mac OS X 10.7 "Lion" ran with

208-725: A 16  MiB ( 16 × 1024 bytes ) address space. 32-bit superminicomputers , such as the DEC VAX , became common in the 1970s, and 32-bit microprocessors, such as the Motorola 68000 family and the 32-bit members of the x86 family starting with the Intel 80386 , appeared in the mid-1980s, making 32 bits something of a de facto consensus as a convenient register size. A 32-bit address register meant that 2 addresses, or 4  GB of random-access memory (RAM), could be referenced. When these architectures were devised, 4 GB of memory

260-423: A 32- or 64-bit Java virtual machine with no modification. The lengths and precision of all the built-in types, such as char , short , int , long , float , and double , and the types that can be used as array indices, are specified by the standard and are not dependent on the underlying architecture. Java programs that run on a 64-bit Java virtual machine have access to a larger address space. Speed

312-609: A 64-bit kernel on more Macs, and OS X 10.8 "Mountain Lion" and later macOS releases only have a 64-bit kernel. On systems with 64-bit processors, both the 32- and 64-bit macOS kernels can run 32-bit user-mode code, and all versions of macOS up to macOS Mojave (10.14) include 32-bit versions of libraries that 32-bit applications would use, so 32-bit user-mode software for macOS will run on those systems. The 32-bit versions of libraries have been removed by Apple in macOS Catalina (10.15). Linux and most other Unix-like operating systems, and

364-780: A driver for a 32-bit PCI device asking the device to DMA data into upper areas of a 64-bit machine's memory could not satisfy requests from the operating system to load data from the device to memory above the 4 gigabyte barrier, because the pointers for those addresses would not fit into the DMA registers of the device. This problem is solved by having the OS take the memory restrictions of the device into account when generating requests to drivers for DMA, or by using an input–output memory management unit (IOMMU). As of August 2023 , 64-bit architectures for which processors are being manufactured include: Most architectures of 64 bits that are derived from

416-449: A generation of computers in which 64-bit processors are the norm. 64 bits is a word size that defines certain classes of computer architecture, buses, memory, and CPUs and, by extension, the software that runs on them. 64-bit CPUs have been used in supercomputers since the 1970s ( Cray-1 , 1975) and in reduced instruction set computers (RISC) based workstations and servers since the early 1990s. In 2003, 64-bit CPUs were introduced to

468-484: A given process and can have implications for efficient processor cache use. Maintaining a partial 32-bit model is one way to handle this, and is in general reasonably effective. For example, the z/OS operating system takes this approach, requiring program code to reside in 31-bit address spaces (the high order bit is not used in address calculation on the underlying hardware platform) while data objects can optionally reside in 64-bit regions. Not all such applications require

520-751: A large address space or manipulate 64-bit data items, so these applications do not benefit from these features. x86-based 64-bit systems sometimes lack equivalents of software that is written for 32-bit architectures. The most severe problem in Microsoft Windows is incompatible device drivers for obsolete hardware. Most 32-bit application software can run on a 64-bit operating system in a compatibility mode , also termed an emulation mode, e.g., Microsoft WoW64 Technology for IA-64 and AMD64. The 64-bit Windows Native Mode driver environment runs atop 64-bit NTDLL.DLL , which cannot call 32-bit Win32 subsystem code (often devices whose actual hardware function

572-521: A problem. 64-bit drivers were not provided for many older devices, which could consequently not be used in 64-bit systems. Driver compatibility was less of a problem with open-source drivers, as 32-bit ones could be modified for 64-bit use. Support for hardware made before early 2007, was problematic for open-source platforms, due to the relatively small number of users. 64-bit versions of Windows cannot run 16-bit software . However, most 32-bit applications will work well. 64-bit users are forced to install

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624-413: A processor with 64-bit memory addresses can directly access 2 bytes (16 exabytes or EB) of byte-addressable memory. With no further qualification, a 64-bit computer architecture generally has integer and addressing registers that are 64 bits wide, allowing direct support for 64-bit data types and addresses. However, a CPU might have external data buses or address buses with different sizes from

676-405: A single integer register can store the memory address to any location in the computer's physical or virtual memory . Therefore, the total number of addresses to memory is often determined by the width of these registers. The IBM System/360 of the 1960s was an early 32-bit computer; it had 32-bit integer registers, although it only used the low order 24 bits of a word for addresses, resulting in

728-434: Is a generational incremental collector. V8 can compile to x86 , ARM or MIPS instruction set architectures in both their 32-bit and 64-bit editions; it has additionally been ported to PowerPC , and to IBM ESA/390 and z/Architecture , for use in servers. V8 can be used in a browser or integrated into independent projects. V8 is used in the following software: JavaScript engine A JavaScript engine

780-469: Is a register based machine and shares a similar (albeit not the exact same) design to the templating interpreter utilized by HotSpot. In 2017, V8 shipped a brand-new compiler pipeline, consisting of Ignition (the interpreter ) and TurboFan (the optimizing compiler ). Starting with V8 version 5.9, Full-codegen (the early baseline compiler) and Crankshaft are no longer used in V8 for JavaScript execution, since

832-588: Is a software component that executes JavaScript code . The first JavaScript engines were mere interpreters , but all relevant modern engines use just-in-time compilation for improved performance. JavaScript engines are typically developed by web browser vendors, and every major browser has one. In a browser, the JavaScript engine runs in concert with the rendering engine via the Document Object Model and Web IDL bindings. However,

884-522: Is an abbreviation of "Long, Pointer, 64". Other models are the ILP64 data model in which all three data types are 64 bits wide, and even the SILP64 model where short integers are also 64 bits wide. However, in most cases the modifications required are relatively minor and straightforward, and many well-written programs can simply be recompiled for the new environment with no changes. Another alternative

936-483: Is emulated in user mode software, like Winprinters). Because 64-bit drivers for most devices were unavailable until early 2007 (Vista x64), using a 64-bit version of Windows was considered a challenge. However, the trend has since moved toward 64-bit computing, more so as memory prices dropped and the use of more than 4 GB of RAM increased. Most manufacturers started to provide both 32-bit and 64-bit drivers for new devices, so unavailability of 64-bit drivers ceased to be

988-413: Is not the only factor to consider in comparing 32-bit and 64-bit processors. Applications such as multi-tasking, stress testing, and clustering – for high-performance computing (HPC) – may be more suited to a 64-bit architecture when deployed appropriately. For this reason, 64-bit clusters have been widely deployed in large organizations, such as IBM, HP, and Microsoft. Summary: A common misconception

1040-441: Is often written with implicit assumptions about the widths of data types. C code should prefer ( u ) intptr_t instead of long when casting pointers into integer objects. A programming model is a choice made to suit a given compiler, and several can coexist on the same OS. However, the programming model chosen as the primary model for the OS application programming interface (API) typically dominates. Another consideration

1092-504: Is often, but not always, based on 64-bit units of data. For example, although the x86 / x87 architecture has instructions able to load and store 64-bit (and 32-bit) floating-point values in memory, the internal floating-point data and register format is 80 bits wide, while the general-purpose registers are 32 bits wide. In contrast, the 64-bit Alpha family uses a 64-bit floating-point data and register format, and 64-bit integer registers. Many computer instruction sets are designed so that

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1144-556: Is strongly inspired by the Java HotSpot Virtual Machine developed by Sun Microsystems , with the newer execution pipelines being very similar to those of HotSpot's. Support for the new WebAssembly language began in 2015. In 2016, the Ignition interpreter was added to V8 with the design goal of reducing the memory usage on small memory Android phones in comparison with TurboFan and Crankshaft. Ignition

1196-418: Is that 64-bit architectures are no better than 32-bit architectures unless the computer has more than 4 GB of random-access memory . This is not entirely true: The main disadvantage of 64-bit architectures is that, relative to 32-bit architectures, the same data occupies more space in memory (due to longer pointers and possibly other types, and alignment padding). This increases the memory requirements of

1248-495: Is the IBM AS/400 , software for which is compiled into a virtual instruction set architecture (ISA) called Technology Independent Machine Interface (TIMI); TIMI code is then translated to native machine code by low-level software before being executed. The translation software is all that must be rewritten to move the full OS and all software to a new platform, as when IBM transitioned the native instruction set for AS/400 from

1300-507: Is the LLP64 model, which maintains compatibility with 32-bit code by leaving both int and long as 32-bit. LL refers to the long long integer type, which is at least 64 bits on all platforms, including 32-bit environments. There are also systems with 64-bit processors using an ILP32 data model, with the addition of 64-bit long long integers; this is also used on many platforms with 32-bit processors. This model reduces code size and

1352-400: Is the data model used for device drivers . Drivers make up the majority of the operating system code in most modern operating systems (although many may not be loaded when the operating system is running). Many drivers use pointers heavily to manipulate data, and in some cases have to load pointers of a certain size into the hardware they support for direct memory access (DMA). As an example,

1404-649: The Apple Watch Series 4 and 5. Many 64-bit platforms today use an LP64 model (including Solaris, AIX , HP-UX , Linux, macOS, BSD, and IBM z/OS). Microsoft Windows uses an LLP64 model. The disadvantage of the LP64 model is that storing a long into an int truncates. On the other hand, converting a pointer to a long will "work" in LP64. In the LLP64 model, the reverse is true. These are not problems which affect fully standard-compliant code, but code

1456-513: The C and C++ toolchains for them, have supported 64-bit processors for many years. Many applications and libraries for those platforms are open-source software , written in C and C++, so that if they are 64-bit-safe, they can be compiled into 64-bit versions. This source-based distribution model, with an emphasis on frequent releases, makes availability of application software for those operating systems less of an issue. In 32-bit programs, pointers and data types such as integers generally have

1508-464: The Cray-1 , used registers up to 64 bits wide, and supported 64-bit integer arithmetic, although they did not support 64-bit addressing. In the mid-1980s, Intel i860 development began culminating in a 1989 release; the i860 had 32-bit integer registers and 32-bit addressing, so it was not a fully 64-bit processor, although its graphics unit supported 64-bit integer arithmetic. However, 32 bits remained

1560-963: The Nintendo 64 and the PlayStation 2 had 64-bit microprocessors before their introduction in personal computers. High-end printers, network equipment, and industrial computers also used 64-bit microprocessors, such as the Quantum Effect Devices R5000 . 64-bit computing started to trickle down to the personal computer desktop from 2003 onward, when some models in Apple 's Macintosh lines switched to PowerPC 970 processors (termed G5 by Apple), and Advanced Micro Devices (AMD) released its first 64-bit x86-64 processor. Physical memory eventually caught up with 32 bit limits. In 2023, laptop computers were commonly equipped with 16GB and servers up to 64 GB of memory, greatly exceeding

1612-521: The 32-bit instruction set, so that processors that support the 64-bit instruction set can also run code for the 32-bit instruction set, or through software emulation , or by the actual implementation of a 32-bit processor core within the 64-bit processor, as with some Itanium processors from Intel, which included an IA-32 processor core to run 32-bit x86 applications. The operating systems for those 64-bit architectures generally support both 32-bit and 64-bit applications. One significant exception to this

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1664-833: The 32-bit limit of 4 GB ( 4 × 1024 bytes ), allowing room for later expansion and incurring no overhead of translating full 64-bit addresses. The Power ISA v3.0 allows 64 bits for an effective address, mapped to a segmented address with between 65 and 78 bits allowed, for virtual memory, and, for any given processor, up to 60 bits for physical memory. The Oracle SPARC Architecture 2015 allows 64 bits for virtual memory and, for any given processor, between 40 and 56 bits for physical memory. The ARM AArch64 Virtual Memory System Architecture allows 48 bits for virtual memory and, for any given processor, from 32 to 48 bits for physical memory. The DEC Alpha specification requires minimum of 43 bits of virtual memory address space (8 TB) to be supported, and hardware need to check and trap if

1716-655: The 4 GB address capacity of 32 bits. In principle, a 64-bit microprocessor can address 16 EB ( 16 × 1024 = 2 = 18,446,744,073,709,551,616 bytes ) of memory. However, not all instruction sets, and not all processors implementing those instruction sets, support a full 64-bit virtual or physical address space. The x86-64 architecture (as of 2016 ) allows 48 bits for virtual memory and, for any given processor, up to 52 bits for physical memory. These limits allow memory sizes of 256  TB ( 256 × 1024 bytes ) and 4  PB ( 4 × 1024 bytes ), respectively. A PC cannot currently contain 4  petabytes of memory (due to

1768-491: The internal V8 bytecode format. TurboFan compiles this bytecode into machine code. In other words, V8 compiles ECMAScript directly to native machine code using just-in-time compilation before executing it. The compiled code is additionally optimized (and re-optimized) dynamically at runtime, based on heuristics of the code's execution profile. Optimization techniques used include inlining , elision of expensive runtime properties, and inline caching . The garbage collector

1820-631: The mainstream PC market in the form of x86-64 processors and the PowerPC G5 . A 64-bit register can hold any of 2 (over 18 quintillion or 1.8×10 ) different values. The range of integer values that can be stored in 64 bits depends on the integer representation used. With the two most common representations, the range is 0 through 18,446,744,073,709,551,615 (equal to 2 − 1) for representation as an ( unsigned ) binary number , and −9,223,372,036,854,775,808 (−2 ) through 9,223,372,036,854,775,807 (2 − 1) for representation as two's complement . Hence,

1872-542: The mid-1990s, HAL Computer Systems , Sun Microsystems , IBM , Silicon Graphics , and Hewlett-Packard had developed 64-bit architectures for their workstation and server systems. A notable exception to this trend were mainframes from IBM, which then used 32-bit data and 31-bit address sizes; the IBM mainframes did not include 64-bit processors until 2000. During the 1990s, several low-cost 64-bit microprocessors were used in consumer electronics and embedded applications. Notably,

1924-409: The norm until the early 1990s, when the continual reductions in the cost of memory led to installations with amounts of RAM approaching 4 GB, and the use of virtual memory spaces exceeding the 4 GB ceiling became desirable for handling certain types of problems. In response, MIPS and DEC developed 64-bit microprocessor architectures, initially for high-end workstation and server machines. By

1976-763: The older 32/48-bit IMPI to the newer 64-bit PowerPC-AS , codenamed Amazon . The IMPI instruction set was quite different from even 32-bit PowerPC, so this transition was even bigger than moving a given instruction set from 32 to 64 bits. On 64-bit hardware with x86-64 architecture (AMD64), most 32-bit operating systems and applications can run with no compatibility issues. While the larger address space of 64-bit architectures makes working with large data sets in applications such as digital video , scientific computing, and large databases easier, there has been considerable debate on whether they or their 32-bit compatibility modes will be faster than comparably priced 32-bit systems for other tasks. A compiled Java program can run on

2028-454: The other browser vendors needed to overhaul their engines for JIT. Apple developed the Nitro engine for its Safari browser, which had 30% better performance than its predecessor. Mozilla then leveraged portions of Nitro to improve SpiderMonkey. Since 2017, these engines have added support for WebAssembly . 64-bit computing From the software perspective, 64-bit computing means

2080-428: The other types of registers cannot. The size of these registers therefore normally limits the amount of directly addressable memory, even if there are registers, such as floating-point registers, that are wider. Most high performance 32-bit and 64-bit processors (some notable exceptions are older or embedded ARM architecture (ARM) and 32-bit MIPS architecture (MIPS) CPUs) have integrated floating point hardware, which

2132-420: The physical size of the memory chips), but AMD envisioned large servers, shared memory clusters, and other uses of physical address space that might approach this in the foreseeable future. Thus the 52-bit physical address provides ample room for expansion while not incurring the cost of implementing full 64-bit physical addresses. Similarly, the 48-bit virtual address space was designed to provide 65,536 (2 ) times

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2184-578: The registers, even larger (the 32-bit Pentium had a 64-bit data bus, for instance). Processor registers are typically divided into several groups: integer , floating-point , single instruction, multiple data (SIMD), control , and often special registers for address arithmetic which may have various uses and names such as address , index , or base registers . However, in modern designs, these functions are often performed by more general purpose integer registers. In most processors, only integer or address-registers can be used to address data in memory;

2236-547: The remaining unsupported bits are zero (to support compatibility on future processors). Alpha 21064 supported 43 bits of virtual memory address space (8 TB) and 34 bits of physical memory address space (16 GB). Alpha 21164 supported 43 bits of virtual memory address space (8 TB) and 40 bits of physical memory address space (1 TB). Alpha 21264 supported user-configurable 43 or 48 bits of virtual memory address space (8 TB or 256 TB) and 44 bits of physical memory address space (16 TB). A change from

2288-486: The same length. This is not necessarily true on 64-bit machines. Mixing data types in programming languages such as C and its descendants such as C++ and Objective-C may thus work on 32-bit implementations but not on 64-bit implementations. In many programming environments for C and C-derived languages on 64-bit machines, int variables are still 32 bits wide, but long integers and pointers are 64 bits wide. These are described as having an LP64 data model , which

2340-448: The size of data structures containing pointers, at the cost of a much smaller address space, a good choice for some embedded systems. For instruction sets such as x86 and ARM in which the 64-bit version of the instruction set has more registers than does the 32-bit version, it provides access to the additional registers without the space penalty. It is common in 64-bit RISC machines, explored in x86 as x32 ABI , and has recently been used in

2392-530: The team believed they were no longer able to keep pace with new JavaScript language features and the optimizations those features required. In 2021, a new tiered compilation pipeline was introduced with the release of the SparkPlug compiler, which supplements the existing TurboFan compiler within V8, in a direct parallel to the profiling C1 Compiler used by HotSpot. In 2023, the Maglev SSA -based compiler

2444-461: The use of machine code with 64-bit virtual memory addresses. However, not all 64-bit instruction sets support full 64-bit virtual memory addresses; x86-64 and AArch64 for example, support only 48 bits of virtual address, with the remaining 16 bits of the virtual address required to be all zeros (000...) or all ones (111...), and several 64-bit instruction sets support fewer than 64 bits of physical memory address. The term 64-bit also describes

2496-480: The use of JavaScript engines is not limited to browsers; for example, the V8 engine is a core component of the Node.js runtime system . Since ECMAScript is the standardized specification of JavaScript, ECMAScript engine is another name for these implementations . With the advent of WebAssembly , some engines can also execute this code in the same sandbox as regular JavaScript code. The first JavaScript engine

2548-475: Was added, which is 10 times slower than Sparkplug but 10 times faster than TurboFan, bridging the gap between Sparkplug and TurboFan for less frequently run loops that do not get "hot" enough to be optimised by TurboFan, as is the case for most web applications that spend more time interacting with the browser than in JavaScript execution. V8 first generates an abstract syntax tree with its own parser. Then, Ignition generates bytecode from this syntax tree using

2600-754: Was created by Brendan Eich in 1995 for the Netscape Navigator web browser . It was a rudimentary interpreter for the nascent language Eich invented. (This evolved into the SpiderMonkey engine, still used by the Firefox browser. ) Google debuted its Chrome browser in 2008, with the V8 JavaScript engine that was faster than its competition. The key innovation was just-in-time compilation (JIT), which Mozilla had also been working on for SpiderMonkey. Because of V8's performance,

2652-534: Was named after the powerful car engine . For several years, Chrome was faster than other browsers at executing JavaScript . The V8 assembler is based on the Strongtalk assembler. On 7 December 2010, a new compiling infrastructure named Crankshaft was released, with speed improvements. In version 41 of Chrome in 2015, project TurboFan was added to provide more performance improvements with previously challenging workloads such as asm.js . Much of V8's development

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2704-416: Was so far beyond the typical amounts (4 MiB) in installations, that this was considered to be enough headroom for addressing. 4.29 billion addresses were considered an appropriate size to work with for another important reason: 4.29 billion integers are enough to assign unique references to most entities in applications like databases . Some supercomputer architectures of the 1970s and 1980s, such as

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