FMOPS (non-widening)

Floating-point outer product, subtracting

The half-precision variant works with a 16-bit element ZA tile.

The single-precision variant works with a 32-bit element ZA tile.

The double-precision variant works with a 64-bit element ZA tile.

This instruction generates an outer product of the first source vector and the second source vector. In case of the half-precision variant, the first source is SVL_H×1 vector and the second source is 1×SVL_H vector. In case of the single-precision variant, the first source is SVL_S×1 vector and the second source is 1×SVL_S vector. In case of the double-precision variant, the first source is SVL_D×1 vector and the second source is 1×SVL_D vector.

Each source vector is independently predicated by a corresponding governing predicate. When either source vector element is Inactive the corresponding destination tile element remains unmodified.

The resulting outer product, SVL_H×SVL_H in case of half-precision variant, SVL_S×SVL_S in case of single-precision variant or SVL_D×SVL_D in case of double-precision variant, is then destructively subtracted from the destination tile. This is equivalent to performing a single multiply-subtract from each of the destination tile elements.

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

ID_AA64SMFR0_EL1.F64F64 indicates whether the double-precision variant is implemented, and ID_AA64SMFR0_EL1.F16F16 indicates whether the half-precision variant is implemented.

It has encodings from 3 classes: Half-precision , Single-precision and Double-precision

Half-precision
(FEAT_SME_F16F16)

Decode for this encoding

if !IsFeatureImplemented(FEAT_SME_F16F16) then EndOfDecode(Decode_UNDEF); end; let esize : integer{} = 16; let a : integer = UInt(Pn); let b : integer = UInt(Pm); let n : integer = UInt(Zn); let m : integer = UInt(Zm); let da : integer = UInt(ZAda);

Single-precision
(FEAT_SME)

Decode for this encoding

if !IsFeatureImplemented(FEAT_SME) then EndOfDecode(Decode_UNDEF); end; let esize : integer{} = 32; let a : integer = UInt(Pn); let b : integer = UInt(Pm); let n : integer = UInt(Zn); let m : integer = UInt(Zm); let da : integer = UInt(ZAda);

Double-precision
(FEAT_SME_F64F64)

Decode for this encoding

if !IsFeatureImplemented(FEAT_SME_F64F64) then EndOfDecode(Decode_UNDEF); end; let esize : integer{} = 64; let a : integer = UInt(Pn); let b : integer = UInt(Pm); let n : integer = UInt(Zn); let m : integer = UInt(Zm); let da : integer = UInt(ZAda);