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]
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.
| Instruction | Description |
|---|---|
ADCX
|
Adds 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. |
ADOX
|
Adds 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. |
References
- ^ "Intel Software Development Emulator". software.intel.com. July 23, 2013. Retrieved October 16, 2013.
- ^ Intel Architecture Instruction Set Extensions Programming Reference (Document number 319433-013B) // Intel, July 2012, Chapter 9: Additional new instructions
- ^ a b "New Instructions Supporting Large Integer Arithmetic on Intel Architecture Processors" (PDF). Intel. Retrieved 2 January 2015.
External links
- Intel Architecture Instruction Set Extensions Programming Reference (PDF). Intel. July 2013. Retrieved 2013-09-10.
- "New Instructions Supporting Large Integer Arithmetic on Intel® Architecture Processors" (PDF).
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