This is a collection of Intel®’ IA32® Software Developer's Manuals (URL of the day) and AMD' AMD64 Architecture Programmer's Manual together with the related specifications, application notes, white papers, and change logs. The collection aims to keep all available revisions. It was originally created by Michal Necasek, see OS/2 Museum.

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VTBL, VTBX

Vector Table Lookup uses byte indexes in a control vector to look up byte values in a table and generate a new vector. Indexes out of range return 0.

Vector Table Extension works in the same way, except that indexes out of range leave the destination element unchanged.

Depending on settings in the CPACR, NSACR, and HCPTR registers, and the Security state and PE mode in which the instruction is executed, an attempt to execute the instruction might be UNDEFINED, or trapped to Hyp mode. For more information see Enabling Advanced SIMD and floating-point support.

It has encodings from the following instruction sets: A32 ( A1 ) and T32 ( T1 ) .

A1

Decode for all variants of this encoding

let is_vtbl : boolean = (op == '0'); let length : integer = UInt(len)+1; let d : integer = UInt(D::Vd); let n : integer = UInt(N::Vn); let m : integer = UInt(M::Vm); if n+length > 32 then UnpredictableProcedure(); end;

CONSTRAINED UNPREDICTABLE behavior

If n + length > 32, then one of the following behaviors must occur:

• The instruction is undefined.
• The instruction executes as NOP.
• One or more of the SIMD and floating-point registers are UNKNOWN. This behavior does not affect any general-purpose registers.

T1

Decode for all variants of this encoding

let is_vtbl : boolean = (op == '0'); let length : integer = UInt(len)+1; let d : integer = UInt(D::Vd); let n : integer = UInt(N::Vn); let m : integer = UInt(M::Vm); if n+length > 32 then UnpredictableProcedure(); end;

CONSTRAINED UNPREDICTABLE behavior

If n + length > 32, then one of the following behaviors must occur:

• The instruction is undefined.
• The instruction executes as NOP.
• One or more of the SIMD and floating-point registers are UNKNOWN. This behavior does not affect any general-purpose registers.

Assembler Symbols