Data processing apparatus and method for performing a shift function on a binary number

A data processing apparatus for performing a shift function on a binary number, comprising:

• count determination circuitry configured to determine a number of contiguous bit positions in the binary number having a predetermined bit value, and to output a count value indicative of said number of contiguous bit positions;
• coarse shifting circuitry configured to determine, for at least one predetermined number of contiguous bit positions, whether said predetermined number of contiguous bit positions within the binary number has said predetermined bit value, and to perform an initial shift operation on the binary number based on said determination in order to produce an intermediate binary number, said coarse shifting circuitry operating in parallel with said count determination circuitry;
• fine shifting circuitry configured to perform a further shift operation on the intermediate binary number, based on the count value output by the count determination circuitry, in order to produce a result binary number;
• and
• an input configured to receive a floating point number comprising a fraction and an exponent, the binary number being determined from said fraction, and said shift function being performed as part of a normalization operation applied to said floating point number;
• wherein said shift function is performed if said floating point number is subnormal;
• wherein the floating point number is determined to be subnormal if the exponent has a predetermined exponent value, and the coarse shifting circuitry is configured to receive the exponent and to cause the initial shift operation to perform no shift on the binary number if the exponent does not have said predetermined exponent value;
• wherein the exponent has said predetermined exponent value if each bit position of said exponent has said predetermined bit value;
• wherein the coarse shifting circuitry is configured to receive as an input value the fraction prepended with the exponent, and the coarse shifting circuitry is configured to evaluate said input value, starting from a first end comprising said exponent, in order to determine, for said at least one predetermined number of contiguous bit positions, whether said predetermined number of contiguous bit positions within the binary number has said predetermined bit value.

A method of operating a data processing apparatus to perform a shift function on a binary number, comprising:

• determining a number of contiguous bit positions in the binary number having a predetermined bit value, and generating a count value indicative of said number of contiguous bit positions;
• employing coarse shifting circuitry to determine, for at least one predetermined number of contiguous bit positions, whether said predetermined number of contiguous bit positions within the binary number has said predetermined bit value, and to perform an initial shift operation on the binary number based on said determination in order to produce an intermediate binary number, the initial shift operation being performed in parallel with the determination of the count value;
• and
• employing fine shifting circuitry to perform a further shift operation on the intermediate binary number, based on the generated count value, in order to produce a result binary number;
• wherein said at least one predetermined number of contiguous bit positions comprises a set of multiple different predetermined numbers of contiguous bit positions, and if a plurality of said multiple different predetermined numbers of contiguous bit positions have said predetermined bit value, the coarse shifting circuitry selects a largest of the predetermined numbers of contiguous bit positions from said plurality, and performs the initial shift operation based on said selected predetermined number of contiguous bit positions.