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. |
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|---|---|
| SIMD (RISC) |
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| SIMD (x86) |
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| Bit manipulation |
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| Compressed instructions |
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| Security and cryptography |
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| Transactional memory |
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| Virtualization |
|
Suspended extensions' dates are | |
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