FMOPS (widening)

Half-precision floating-point sum of outer products and subtract

The half-precision floating-point sum of outer products and subtract instruction works with a 32-bit element ZA tile.

This instruction widens the SVL_S×2 sub-matrix of half-precision floating-point values held in the first source vector to single-precision floating-point values and multiplies it by the widened 2×SVL_S sub-matrix of half-precision floating-point values in the second source vector to single-precision floating-point values.

Each source vector is independently predicated by a corresponding governing predicate. When a 16-bit source element is Inactive it is treated as having the value +0.0, but if both pairs of source vector elements that correspond to a 32-bit destination element contain Inactive elements, then the destination element remains unmodified.

The resulting SVL_S×SVL_S single-precision floating-point sum of outer products is then destructively subtracted from the single-precision floating-point destination tile. This is equivalent to performing a 2-way dot product and subtract from each of the destination tile elements.

Each 32-bit container of the first source vector holds 2 consecutive column elements of each row of a SVL_S×2 sub-matrix. Similarly, each 32-bit container of the second source vector holds 2 consecutive row elements of each column of a 2×SVL_S sub-matrix.

This instruction follows SME ZA-targeting floating-point behaviors.

SME
(FEAT_SME)

if !HaveSME() then UNDEFINED; integer a = UInt(Pn); integer b = UInt(Pm); integer n = UInt(Zn); integer m = UInt(Zm); integer da = UInt(ZAda); boolean sub_op = TRUE;