Base Instructions | SIMD&FP Instructions | SVE Instructions | SME Instructions | Index by Encoding | Shared Pseudocode | Proprietary Notice

## LDFF1SW (scalar plus vector)

Gather load first-fault signed words to vector (vector index)

Gather load with first-faulting behavior of signed words to active elements of a vector register from memory addresses generated by a 64-bit scalar base plus vector index. The index values are optionally first sign or zero-extended from 32 to 64 bits and then optionally multiplied by 4. Inactive elements will not cause a read from Device memory or signal faults, and are set to zero in the destination vector.

This instruction is illegal when executed in Streaming SVE mode, unless FEAT_SME_FA64 is implemented and enabled.

It has encodings from 4 classes: 32-bit unpacked scaled offset , 32-bit unpacked unscaled offset , 64-bit scaled offset and 64-bit unscaled offset

### 32-bit unpacked scaled offset

31 | 30 | 29 | 28 | 27 | 26 | 25 | 24 | 23 | 22 | 21 | 20 | 19 | 18 | 17 | 16 | 15 | 14 | 13 | 12 | 11 | 10 | 9 | 8 | 7 | 6 | 5 | 4 | 3 | 2 | 1 | 0
1 | 1 | 0 | 0 | 0 | 1 | 0 | 1 | 0 | xs | 1 | Zm | 0 | 0 | 1 | Pg | Rn | Zt
|  |  |  |  |  |  | U | ff |  |  |

####

LDFF1SW { <Zt>.D }, <Pg>/Z, [<Xn|SP>, <Zm>.D, <mod> #2]

if !HaveSVE() then UNDEFINED; integer t = UInt(Zt); integer n = UInt(Rn); integer m = UInt(Zm); integer g = UInt(Pg); constant integer esize = 64; constant integer msize = 32; constant integer offs_size = 32; boolean unsigned = FALSE; boolean offs_unsigned = xs == '0'; integer scale = 2;

### 32-bit unpacked unscaled offset

31 | 30 | 29 | 28 | 27 | 26 | 25 | 24 | 23 | 22 | 21 | 20 | 19 | 18 | 17 | 16 | 15 | 14 | 13 | 12 | 11 | 10 | 9 | 8 | 7 | 6 | 5 | 4 | 3 | 2 | 1 | 0
1 | 1 | 0 | 0 | 0 | 1 | 0 | 1 | 0 | xs | 0 | Zm | 0 | 0 | 1 | Pg | Rn | Zt
| msz<1> | msz<0> |  |  |  |  | U | ff |  |  |

####

LDFF1SW { <Zt>.D }, <Pg>/Z, [<Xn|SP>, <Zm>.D, <mod>]

if !HaveSVE() then UNDEFINED; integer t = UInt(Zt); integer n = UInt(Rn); integer m = UInt(Zm); integer g = UInt(Pg); constant integer esize = 64; constant integer msize = 32; constant integer offs_size = 32; boolean unsigned = FALSE; boolean offs_unsigned = xs == '0'; integer scale = 0;

### 64-bit scaled offset

31 | 30 | 29 | 28 | 27 | 26 | 25 | 24 | 23 | 22 | 21 | 20 | 19 | 18 | 17 | 16 | 15 | 14 | 13 | 12 | 11 | 10 | 9 | 8 | 7 | 6 | 5 | 4 | 3 | 2 | 1 | 0
1 | 1 | 0 | 0 | 0 | 1 | 0 | 1 | 0 | 1 | 1 | Zm | 1 | 0 | 1 | Pg | Rn | Zt
|  |  |  |  |  | U | ff |  |  |

####

LDFF1SW { <Zt>.D }, <Pg>/Z, [<Xn|SP>, <Zm>.D, LSL #2]

if !HaveSVE() then UNDEFINED; integer t = UInt(Zt); integer n = UInt(Rn); integer m = UInt(Zm); integer g = UInt(Pg); constant integer esize = 64; constant integer msize = 32; constant integer offs_size = 64; boolean unsigned = FALSE; boolean offs_unsigned = TRUE; integer scale = 2;

### 64-bit unscaled offset

31 | 30 | 29 | 28 | 27 | 26 | 25 | 24 | 23 | 22 | 21 | 20 | 19 | 18 | 17 | 16 | 15 | 14 | 13 | 12 | 11 | 10 | 9 | 8 | 7 | 6 | 5 | 4 | 3 | 2 | 1 | 0
1 | 1 | 0 | 0 | 0 | 1 | 0 | 1 | 0 | 1 | 0 | Zm | 1 | 0 | 1 | Pg | Rn | Zt
| msz<1> | msz<0> |  |  |  | U | ff |  |  |

####

LDFF1SW { <Zt>.D }, <Pg>/Z, [<Xn|SP>, <Zm>.D]

if !HaveSVE() then UNDEFINED; integer t = UInt(Zt); integer n = UInt(Rn); integer m = UInt(Zm); integer g = UInt(Pg); constant integer esize = 64; constant integer msize = 32; constant integer offs_size = 64; boolean unsigned = FALSE; boolean offs_unsigned = TRUE; integer scale = 0;

### Assembler Symbols

<Zt> | Is the name of the scalable vector register to be transferred, encoded in the "Zt" field.

<Pg> | Is the name of the governing scalable predicate register P0-P7, encoded in the "Pg" field.

<Xn|SP> | Is the 64-bit name of the general-purpose base register or stack pointer, encoded in the "Rn" field.

<Zm> | Is the name of the offset scalable vector register, encoded in the "Zm" field.

<mod> | Is the index extend and shift specifier, encoded in xs:
xs | <mod>
--- | ---
0 | UXTW
1 | SXTW

### Operation

CheckNonStreamingSVEEnabled(); constant integer VL = CurrentVL; constant integer PL = VL DIV 8; constant integer elements = VL DIV esize; bits(PL) mask = P[g, PL]; bits(64) base; bits(VL) offset; bits(VL) result; bits(VL) orig = Z[t, VL]; bits(msize) data; constant integer mbytes = msize DIV 8; boolean fault = FALSE; boolean faulted = FALSE; boolean unknown = FALSE; boolean contiguous = FALSE; boolean tagchecked = TRUE; AccessDescriptor accdesc = CreateAccDescSVEFF(contiguous, tagchecked); if !AnyActiveElement(mask, esize) then if n == 31 && ConstrainUnpredictableBool(Unpredictable_CHECKSPNONEACTIVE) then CheckSPAlignment(); else if n == 31 then CheckSPAlignment(); base = if n == 31 then SP[] else X[n, 64]; offset = Z[m, VL]; assert accdesc.first; for e = 0 to elements-1 if ActivePredicateElement(mask, e, esize) then integer off = Int(Elem[offset, e, esize]<offs_size-1:0>, offs_unsigned); bits(64) addr = base + (off << scale); if accdesc.first then // Mem[] will not return if a fault is detected for the first active element data = Mem[addr, mbytes, accdesc]; accdesc.first = FALSE; else // MemNF[] will return fault=TRUE if access is not performed for any reason (data, fault) = MemNF[addr, mbytes, accdesc]; else (data, fault) = (Zeros(msize), FALSE); // FFR elements set to FALSE following a supressed access/fault faulted = faulted || fault; if faulted then ElemFFR[e, esize] = '0'; // Value becomes CONSTRAINED UNPREDICTABLE after an FFR element is FALSE unknown = unknown || ElemFFR[e, esize] == '0'; if unknown then if !fault && ConstrainUnpredictableBool(Unpredictable_SVELDNFDATA) then Elem[result, e, esize] = Extend(data, esize, unsigned); elsif ConstrainUnpredictableBool(Unpredictable_SVELDNFZERO) then Elem[result, e, esize] = Zeros(esize); else // merge Elem[result, e, esize] = Elem[orig, e, esize]; else Elem[result, e, esize] = Extend(data, esize, unsigned); Z[t, VL] = result;

Base Instructions | SIMD&FP Instructions | SVE Instructions | SME Instructions | Index by Encoding | Shared Pseudocode | Proprietary Notice

Internal version only: isa v33.64, AdvSIMD v29.12, pseudocode v2023-06_rel, sve v2023-06_rel ; Build timestamp: 2023-07-04T19:42

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