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The REX prefix provides additional space for encoding 64-bit addressing modes and additional registers present in the x86-64 architecture. Bit-field W changes the operand size to 64 bits, R expands reg to 4 bits, B expands r/m (or opreg in the few opcodes that encode the register in the 3 lowest opcode bits, such as "POP reg"), and X and B expand index and base in the SIB byte.
The EVEX prefix retains fields introduced in the VEX prefix: Four bits R̅, X̅, B̅ and W from the VEX prefix, stored in inverted form. W expands the operand size to 64 bits or serves as an additional opcode, R expands reg, B expands r/m or reg, and X and B expand index and base in the SIB byte. Four bits named v̅, stored in inverted form.
The TBM instructions are all encoded using the XOP prefix. They are all available in 32-bit and 64-bit forms, selected with the XOP.W bit (0=32bit, 1=64bit). (XOP.W is ignored outside 64-bit mode.) Like all instructions encoded with VEX/XOP prefixes, they are unavailable in Real Mode and Virtual-8086 mode.
Unlike the rest of the AVX-512 instructions, these instructions are all VEX encoded. The initial opmask instructions are all 16-bit (Word) versions. With AVX-512DQ 8-bit (Byte) versions were added to better match the needs of masking 8 64-bit values, and with AVX-512BW 32-bit (Double) and 64-bit (Quad) versions were added so they can mask up to ...
Bit manipulation instructions. For all of the VEX-encoded instructions defined by BMI1 and BMI2, the operand size may be 32 or 64 bits, controlled by the VEX.W bit – none of these instructions are available in 16-bit variants. The VEX-encoded instructions are not available in Real Mode and Virtual-8086 mode - other than that, the bit ...
Caleb Williams gained a shot of confidence and Cairo Santos earned a measure of redemption. The Chicago Bears finished a disappointing season on a high note, while the Green Bay Packers limped ...
AMD was the first to introduce the instructions that now form Intel's BMI1 as part of its ABM (Advanced Bit Manipulation) instruction set, then later added support for Intel's new BMI2 instructions. AMD today advertises the availability of these features via Intel's BMI1 and BMI2 cpuflags and instructs programmers to target them accordingly.
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