FSUB

Floating-point subtract multi-vector from ZA array vector accumulators

Destructively subtract all elements of the two or four source vectors from the corresponding elements of the ZA single-vector groups.

The single-vector group within each half of or each quarter of the ZA array is selected by the sum of the vector select register and offset, modulo half or quarter the number of ZA array vectors.

The vector group symbol, VGx2 or VGx4, indicates that the ZA operand consists of two or four ZA single-vector groups respectively. The vector group symbol is preferred for disassembly, but optional in assembler source code.

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

This instruction is unpredicated.

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 4 classes: Two ZA single-vectors , Two ZA single-vectors of half precision elements , Four ZA single-vectors and Four ZA single-vectors of half precision elements

Two ZA single-vectors
(FEAT_SME2)

if !IsFeatureImplemented(FEAT_SME2) then UNDEFINED; if sz == '1' && !IsFeatureImplemented(FEAT_SME_F64F64) then UNDEFINED; constant integer v = UInt('010':Rv); constant integer esize = 32 << UInt(sz); constant integer m = UInt(Zm:'0'); constant integer offset = UInt(off3); constant integer nreg = 2;

Two ZA single-vectors of half precision elements
(FEAT_SME_F16F16)

if !IsFeatureImplemented(FEAT_SME_F16F16) && !IsFeatureImplemented(FEAT_SME_F8F16) then UNDEFINED; constant integer v = UInt('010':Rv); constant integer esize = 16; constant integer m = UInt(Zm:'0'); constant integer offset = UInt(off3); constant integer nreg = 2;

Four ZA single-vectors
(FEAT_SME2)

if !IsFeatureImplemented(FEAT_SME2) then UNDEFINED; if sz == '1' && !IsFeatureImplemented(FEAT_SME_F64F64) then UNDEFINED; constant integer v = UInt('010':Rv); constant integer esize = 32 << UInt(sz); constant integer m = UInt(Zm:'00'); constant integer offset = UInt(off3); constant integer nreg = 4;

Four ZA single-vectors of half precision elements
(FEAT_SME_F16F16)

if !IsFeatureImplemented(FEAT_SME_F16F16) && !IsFeatureImplemented(FEAT_SME_F8F16) then UNDEFINED; constant integer v = UInt('010':Rv); constant integer esize = 16; constant integer m = UInt(Zm:'00'); constant integer offset = UInt(off3); constant integer nreg = 4;