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AVX-512

AVX512-K20 exception class

VEX-encoded instructions on opmask registers without a memory operand, such as KANDW, KORTESTQ and KSHIFTLD, which Intel's manual calls Exceptions Type K20.

Class
AVX512-K20 in Intel XED
Applies to
VEX encodings on opmask and general-purpose registers.
Instructions
51 mnemonics, 54 forms
Data
Intel XED v2026.08.23

Exception conditions

When an instruction of the class raises each exception, and in which processor modes. Protected mode includes compatibility mode. How to read the table.
ExceptionRealVirtual-8086Protected64-bitCondition
#UDThe processor lacks the instruction’s extension: its CPUID feature flag is 0.
#UDAlways: real and virtual-8086 mode have no VEX prefix.
#UDThe operating system has not enabled the opmask state: CR4.OSXSAVE is 0, or XCR0 lacks one of the bits that Table 2-39 requires.
#UDA VEX field has a value that the manual’s general rules forbid (Tables 2-40 and 2-41).
#UDA REX, F2, F3 or 66 prefix comes before the VEX prefix.
#UDThe ModR/M byte encodes a memory operand (its mod field is not 11b).
#NMCR0.TS (task switched, bit 3) is 1.

Notes

Without a memory operand, only #UD and #NM remain. The moves from a mask register to a general-purpose register (KMOVB, KMOVW, KMOVD and KMOVQ) are here; their other forms are AVX512-K21.

  • AVX512-K21: The VEX-encoded opmask moves KMOVB, KMOVW, KMOVD and KMOVQ in the forms that can address memory, which Intel's manual calls Exceptions Type K21.

Instructions

Intel XED puts forms of 51 mnemonics in this class, listed here by extension. Where a mnemonic also has forms of other classes, its link leads to its first form of this one.

AVX10.1

Sources

  1. Intel 64 and IA-32 Architectures Software Developer's Manual, Volume 2 (325383-093, September 2026): Section 2.9.1, Table 2-65; Section 2.7.11, Tables 2-39 to 2-41.
  2. Intel XED v2026.08.23 (commit 0bcb6237345c): the exception class of each instruction form.

The list of instructions is derived from Intel XED, Copyright Intel Corporation, licensed under the Apache License 2.0; x86-64.net converted and reformatted it. The text is our own.