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CLZ

Count Leading Zeros returns the number of binary zero bits before the first binary one bit in a value.

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

A1

Decode for this encoding

let d : integer = UInt(Rd); let m : integer = UInt(Rm); if d == 15 || m == 15 then UnpredictableProcedure(); end;

T1

Decode for this encoding

let d : integer = UInt(Rd); let m : integer = UInt(Rm); let n : integer = UInt(Rn); // Armv8-A removes UNPREDICTABLE for R13 if m != n || d == 15 || m == 15 then UnpredictableProcedure(); end;

CONSTRAINED UNPREDICTABLE behavior

If m != n, then one of the following behaviors must occur:

• The instruction is undefined.
• The instruction executes as NOP.
• The instruction executes as described, with no change to its behavior and no additional side effects.
• The instruction executes with the additional decode: m = UInt(Rn);.
• The value in the destination register is unknown.

Assembler Symbols