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FMLA (indexed)

Floating-point fused multiply-add by indexed elements (Zda = Zda + Zn * Zm[indexed]).

Multiply all floating-point elements within each 128-bit segment of the first source vector by the specified element in the corresponding second source vector segment. The products are then destructively added without intermediate rounding to the corresponding elements of the addend and destination vector.

The elements within the second source vector are specified using an immediate index which selects the same element position within each 128-bit vector segment. The index range is from 0 to one less than the number of elements per 128-bit segment, encoded in 1 to 3 bits depending on the size of the element. This instruction is unpredicated.

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

Half-precision

313029282726252423222120191817161514131211109876543210
011001000i3h1i3lZm000000ZnZda

Half-precision

FMLA <Zda>.H, <Zn>.H, <Zm>.H[<imm>]

if !HaveSVE() then UNDEFINED;
integer esize = 16;
integer index = UInt(i3h:i3l);
integer n = UInt(Zn);
integer m = UInt(Zm);
integer da = UInt(Zda);
boolean op1_neg = FALSE;
boolean op3_neg = FALSE;

Single-precision

313029282726252423222120191817161514131211109876543210
01100100101i2Zm000000ZnZda

Single-precision

FMLA <Zda>.S, <Zn>.S, <Zm>.S[<imm>]

if !HaveSVE() then UNDEFINED;
integer esize = 32;
integer index = UInt(i2);
integer n = UInt(Zn);
integer m = UInt(Zm);
integer da = UInt(Zda);
boolean op1_neg = FALSE;
boolean op3_neg = FALSE;

Double-precision

313029282726252423222120191817161514131211109876543210
01100100111i1Zm000000ZnZda

Double-precision

FMLA <Zda>.D, <Zn>.D, <Zm>.D[<imm>]

if !HaveSVE() then UNDEFINED;
integer esize = 64;
integer index = UInt(i1);
integer n = UInt(Zn);
integer m = UInt(Zm);
integer da = UInt(Zda);
boolean op1_neg = FALSE;
boolean op3_neg = FALSE;

Assembler Symbols

<Zda>

Is the name of the third source and destination scalable vector register, encoded in the "Zda" field.

<Zn>

Is the name of the first source scalable vector register, encoded in the "Zn" field.

<Zm>

For the half-precision and single-precision variant: is the name of the second source scalable vector register Z0-Z7, encoded in the "Zm" field.

For the double-precision variant: is the name of the second source scalable vector register Z0-Z15, encoded in the "Zm" field.

<imm>

For the half-precision variant: is the immediate index, in the range 0 to 7, encoded in the "i3h:i3l" fields.

For the single-precision variant: is the immediate index, in the range 0 to 3, encoded in the "i2" field.

For the double-precision variant: is the immediate index, in the range 0 to 1, encoded in the "i1" field.

Operation

CheckSVEEnabled();
integer elements = VL DIV esize;
integer eltspersegment = 128 DIV esize;
bits(VL) operand1 = Z[n];
bits(VL) operand2 = Z[m];
bits(VL) result = Z[da];

for e = 0 to elements-1
    integer segmentbase = e - e MOD eltspersegment;
    integer s = segmentbase + index;
    bits(esize) element1 = Elem[operand1, e, esize];
    bits(esize) element2 = Elem[operand2, s, esize];
    bits(esize) element3 = Elem[result, e, esize];
    if op1_neg then element1 = FPNeg(element1);
    if op3_neg then element3 = FPNeg(element3);
    Elem[result, e, esize] = FPMulAdd(element3, element1, element2, FPCR);

Z[da] = result;

Operational information

This instruction might be immediately preceded in program order by a MOVPRFX instruction that conforms to all of the following requirements, otherwise the behavior of either or both instructions is unpredictable:

  • The MOVPRFX instruction must specify the same destination register as this instruction.
  • The destination register must not refer to architectural register state referenced by any other source operand register of this instruction.
The MOVPRFX instructions that can be used with this instruction are as follows:
  • An unpredicated MOVPRFX instruction.