Intel ADX

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Intel ADX (Multi-Precision Add-Carry Instruction Extensions) is Intel's arbitrary-precision arithmetic extension to the x86 instruction set architecture (ISA). Intel ADX was first supported in the Broadwell microarchitecture. [1] [2]

Intel American semiconductor company

Intel Corporation is an American multinational corporation and technology company headquartered in Santa Clara, California, in the Silicon Valley. It is the world's second largest and second highest valued semiconductor chip manufacturer based on revenue after being overtaken by Samsung, and is the inventor of the x86 series of microprocessors, the processors found in most personal computers (PCs). Intel ranked No. 46 in the 2018 Fortune 500 list of the largest United States corporations by total revenue.

In computer science, arbitrary-precision arithmetic, also called bignum arithmetic, multiple-precision arithmetic, or sometimes infinite-precision arithmetic, indicates that calculations are performed on numbers whose digits of precision are limited only by the available memory of the host system. This contrasts with the faster fixed-precision arithmetic found in most arithmetic logic unit (ALU) hardware, which typically offers between 8 and 64 bits of precision.

x86 family of instruction set architectures

x86 is a family of instruction set architectures based on the Intel 8086 microprocessor and its 8088 variant. The 8086 was introduced in 1978 as a fully 16-bit extension of Intel's 8-bit 8080 microprocessor, with memory segmentation as a solution for addressing more memory than can be covered by a plain 16-bit address. The term "x86" came into being because the names of several successors to Intel's 8086 processor end in "86", including the 80186, 80286, 80386 and 80486 processors.

The instruction set extension contains just two new instructions, though MULX from BMI2 is also considered as a part of the large integer arithmetic support. [3]

Both instructions are more efficient variants of the existing ADC instruction, with the difference that each of the two new instructions affects only one flag, where ADC as a signed addition may set both overflow and carry flags, and as an old-style x86 instruction also reset the rest of the CPU flags. Having two versions affecting different flags means that two chains of additions with carry can be calculated in parallel. [3]

AMD added support in their processors for these instructions starting with Ryzen.

Ryzen is a brand of x64 and x86 microprocessors designed and marketed by AMD for desktop, mobile and embedded platform based on Zen and Zen+ microarchitectures. It consists of central processing units marketed for mainstream, enthusiast and workstation segments and accelerated processing units (APUs) which is marketed for mainstream and entry-level segments and embedded applications.

InstructionDescription
ADCXAdds two unsigned integers plus carry, reading the carry from the carry flag and if necessary setting it there. Does not affect other flags than the carry.
ADOXAdds two unsigned integers plus carry, reading the carry from the overflow flag and if necessary setting it there. Does not affect other flags than the overflow.

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References

  1. "Intel Software Development Emulator". software.intel.com. July 23, 2013. Retrieved October 16, 2013.
  2. Intel Architecture Instruction Set Extensions Programming Reference (Document number 319433-013B) // Intel, July 2012, Chapter 9: Additional new instructions
  3. 1 2 "New Instructions Supporting Large Integer Arithmetic on Intel Architecture Processors" (PDF). Intel . Retrieved 2 January 2015.