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UBFX

Unsigned Bit Field Extract extracts any number of adjacent bits at any position from a register, zero-extends them to 32 bits, and writes the result to the destination register.

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

A1

Decode for this encoding

let d : integer = UInt(Rd); let n : integer = UInt(Rn); let lsbit : integer{} = UInt(lsb); let widthminus1 : integer{} = UInt(widthm1); let msbit : integer{} = lsbit + widthminus1; if d == 15 || n == 15 then UnpredictableProcedure(); end; if msbit > 31 then UnpredictableProcedure(); end;

CONSTRAINED UNPREDICTABLE behavior

If msbit > 31, then one of the following behaviors must occur:

• The instruction is undefined.
• The instruction executes as NOP.
• The value in the destination register is unknown.

T1

Decode for this encoding

let d : integer = UInt(Rd); let n : integer = UInt(Rn); let lsbit : integer{} = UInt(imm3::imm2); let widthminus1 : integer{} = UInt(widthm1); let msbit : integer{} = lsbit + widthminus1; // Armv8-A removes UNPREDICTABLE for R13 if d == 15 || n == 15 then UnpredictableProcedure(); end; if msbit > 31 then UnpredictableProcedure(); end;

CONSTRAINED UNPREDICTABLE behavior

If msbit > 31, then one of the following behaviors must occur:

• The instruction is undefined.
• The instruction executes as NOP.
• The value in the destination register is unknown.

Assembler Symbols