Sun Microsystems, Inc.

Imagination Technologies Limited

Oracle America, Inc.

Other

Arm Finance Overseas Limited

Leonard D Rarick

Christopher Hans Olson

Gregory Frederick Grohoski

Manouk Vartan Manoukian

Sheueling Chang Shantz

Murali Krishna Inaganti

Lawrence Spracklen

Hans Eberle

Nils Gura

Kristie Veith

Shailender Chaudhry

Paul Caprioli

Allen Lyu

Shu-Chin Tai

Shreyas Sundaram

In an aspect, a processor includes circuitry for iterative refinement approaches, e.g., Newton-Raphson, to evaluating functions, such as square root, reciprocal, and for division. The circuitry includes circuitry for producing an initial approximation; which can include a LookUp Table (LUT). LUT may produce an output that (with implementation-dependent processing) forms an initial approximation of a value, with a number of bits of precision. A limited-precision multiplier multiplies that initial approximation with another value; an output of the limited precision multiplier goes to a full precision multiplier circuit that performs remaining multiplications required for iteration(s) in the particular refinement process being implemented. For example, in division, the output being calculated is for a reciprocal of the divisor. The full-precision multiplier circuit requires a first number of clock cycles to complete, and both the small multiplier and the initial approximation circuitry complete within the first number of clock cycles.

Small multiplier after initial approximation for operations with increasing precision

Method and computer system for implementing an operation on &#x2265;1 floating point input, in accordance with a rounding mode, e.g. using a Newton-Raphson technique. The floating point result comprises a p-bit mantissa. An unrounded proposed mantissa result is determined using the Newton-Raphson technique, wherein a p-bit rounded proposed mantissa result, t, corresponds to a rounding of the unrounded proposed mantissa result in accordance with the rounding mode, with k leading zeroes. If an increment to the (m&#x2212;k)bit of the unrounded result would affect the p-bit rounded result then the input(s) and bits of the unrounded result are used to determine a check parameter which is indicative of a relationship between an exact result and the unrounded result if the (m&#x2212;k)bit were incremented. The p-bit mantissa of the floating point result, is determined in dependence upon the check parameter, to be either t or t+1.

Check procedure for floating point operations

Embodiments disclosed pertain to apparatuses, systems, and methods for performing multi-precision single instruction multiple data (SIMD) operations on integer, fixed point and floating point operands. Disclosed embodiments pertain to a circuit that is capable of performing concurrent multiply, fused multiply-add, rounding, saturation, and dot products on the above operand types. In addition, the circuit may facilitate 64-bit multiplication when Newton-Raphson, divide and square root operations are performed.

Unified multiply unit

Embodiments disclosed pertain to apparatuses, systems, and methods for floating point operations. Disclosed embodiments pertain to a circuit that is capable of processing both a normal and denormal inputs and outputting normal and denormal results, and where a rounding module is used advantageously to reduce operational latency of the circuit.

Rounding floating point numbers

A method and computer system are provided for performing a comparison computation, e.g. for use in a check procedure for a reciprocal square root operation. The comparison computation compares a multiplication of three values with a predetermined value. The computer system performs the multiplication using multiplier logic which is configured to perform multiply operations in which two values are multiplied together. A first and second of the three values are multiplied to determine a first intermediate result, w. The digits of ware separated into two portions, wand w. The third of the three values is multiplied with wand the result is added into a multiplication of the third of the three values with wto thereby determine the result of multiplying the three values together. In this way the comparison is performed with high accuracy, while keeping the area and power consumption of the multiplier logic low.

Performing a comparison computation in a computer system

In an aspect, a pipelined execution resource can produce an intermediate result for use in an iterative approximation algorithm in an odd number of clock cycles. The pipelined execution resource executes SIMD requests by staggering commencement of execution of the requests from a SIMD instruction. When executing one or more operations for a SIMD iterative approximation algorithm, and an operation for another SIMD iterative approximation algorithm is ready to begin execution, control logic causes intermediate results completed by the pipelined execution resource to pass through a wait state, before being used in a subsequent computation. This wait state presents two open scheduling cycles in which both parts of the next SIMD instruction can begin execution. Although the wait state increases latency to complete an in-progress algorithm, a total throughput of execution on the pipeline increases.

Variable length execution pipeline

Method and computer system for implementing an operation on &#x2267;1 floating point input, in accordance with a rounding mode, e.g. using a Newton-Raphson technique. The floating point result comprises a p-bit mantissa. An unrounded proposed mantissa result is determined using the Newton-Raphson technique, wherein a p-bit rounded proposed mantissa result, t, corresponds to a rounding of the unrounded proposed mantissa result in accordance with the rounding mode, with k leading zeroes. If an increment to the (m&#x2212;k)bit of the unrounded result would affect the p-bit rounded result then the input(s) and bits of the unrounded result are used to determine a check parameter which is indicative of a relationship between an exact result and the unrounded result if the (m&#x2212;k)bit were incremented. The p-bit mantissa of the floating point result, is determined in dependence upon the check parameter, to be either t or t+1.

A method and computer system are provided for implementing a square root operation using an iterative converging approximation technique. The method includes fewer computations than conventional methods, and only includes computations which are simple to implement in hardware on a computer system, such as multiplication, addition, subtraction and shifting. Therefore, the methods described herein are adapted specifically for being performed on a computer system, e.g. in hardware, and allow the computer system to perform a square root operation with low latency and with low power consumption.

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San Jose, CA, United States of America

Leonard D Rarick