Abstract: The present invention relates to a method and circuit for performing multiply-operations in an arithmetic unit of a computer processor. In a multiplier thereof, zero detection of the resulting product bit string (22) is needed for a proper setting of condition code and overflow status information. Zero detection according to prior art decreases the calculation speed in the multiplier. In order to provide a method and respective electronic circuit, wherein the zero detection is earlier completed, it is proposed to use a leading zero anticipation (LZA) hardware—i.e., an LZA circuit (40), which exists usually anyway in floating point processor adders for calculating the number of leading zeros for operand normalization purposes—for performing a zero detection of the product by aid of the partial results (16, 17) emerging at the output of the Wallace tree of the multiplier.

Abstract: A system for performing floating point arithmetic operations including an input register adapted for receiving an operand. The system also includes a mechanism for performing a shift or masking operation in response to determining that the operand is in an un-normalized format. The system also includes instructions for performing single precision incrementing of the operand in response to determining that the operand is single precision, that the operand requires the incrementing based on the results of a previous operation and that the previous operation did not perform the incrementing. The operand was created in the previous operation. The system further includes instructions for performing double precision incrementing of the operand in response to determining that the operand is double precision, that the operand requires the incrementing based on the results of the previous operation and that the previous operation did not perform the incrementing.

Abstract: A system for performing floating point arithmetic operations including an input register adapted for receiving an operand. The system also includes computer instructions for performing single precision incrementing of the operand in response to determining that the operand is single precision, that the operand requires the incrementing based on the results of a previous operation and that the previous operation did not perform the incrementing. The operand was created in the previous operation. The system further includes instructions for performing double precision incrementing of the operand in response to determining that the operand is double precision, that the operand requires the incrementing based on the results of the previous operation and that the previous operation did not perform the incrementing.

Abstract: A system and method for executing fixed point divide operations using a floating point multiply-add pipeline are provided. With the system and method, the floating point execution unit in a processor is modified to include elements that may be used to perform fixed point divide operations. These additional elements include a leading zero counter, a leading one counter, an estimate table unit, and a state machine. The fixed point divide operands are converted to a floating point format and an estimate of the reciprocal of the divisor is generated using estimate tables. These values are used in multiple passes through the floating point unit for calculating estimates of the quotient and corresponding error values. The estimates of the quotient are based on previous estimates of the quotient in a prior pass through the floating point unit and a corresponding error value. The final quotient estimate is truncated.

Abstract: A system and method for handling denormal floating point operands when the result must be normalized. A leading zero counter (lzc) on the operand B (opB) is used to limit alignment shifts when opB is denormal but is much greater than the product of operands A and C, i.e. AC. By limiting the additional shift of B during normalization, by the number of leading zeros in opB, no increase is needed in the output bus of the alignment shifter. Furthermore, the additional shift may be done either in the alignment shifter, or postponed to a later stage in the pipeline, where the result is normalized.

Abstract: A method of processing data employs a new rounding mode called “round for reround” on the original arithmetic instruction in the hardware precision, and then 2) invoking an instruction which specifies a variable rounding precision and possibly explicitly sets the rounding mode which we have called the ReRound instruction. The precise result of the arithmetic operation is first truncated to the hardware format precision “p”, forming an intermediate result. If only zeros are dropped during truncation, then the intermediate result is equal to the precise result, and this result is said to be “exact”, otherwise, it is “inexact”. When the intermediate result is inexact and its least significant digit is either zero or five, then that digit is incremented to one or six respectively forming the rounded result.

Abstract: A method of discovering a fault in a circuit is disclosed. The method comprises generating a first result of a selected function by performing the selected function on an operand, wherein the selected function employs a mask. Once the function is performed, an antimask of the mask is created, and the modulo of the antimask is calculated. A modulo function of the first result of the selected function is calculated to obtain a third result. A modulo of the operand is then calculated to obtain a fourth result, and a second function is then performed on the second result and the third result to obtain a fifth result. In response to comparing the fifth result to the fourth result, a signal is propagated to indicate a fault in the circuit.