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FMLALT (indexed)

Half-precision floating-point multiply-add long to single-precision (top, indexed).

This half-precision floating-point multiply-add long instruction widens the odd-numbered 16-bit half-precision elements in the first source vector and the indexed element from the corresponding 128-bit segment in the second source vector to single-precision format and then destructively multiplies and adds these values without intermediate rounding to the overlapping 32-bit single-precision elements of the addend and destination vector. This instruction is unpredicated.



FMLALT <Zda>.S, <Zn>.H, <Zm>.H[<imm>]

if !HaveSVE2() then UNDEFINED;
integer esize = 32;
integer n = UInt(Zn);
integer m = UInt(Zm);
integer da = UInt(Zda);
integer index = UInt(i3h:i3l);
boolean op1_neg = FALSE;

Assembler Symbols


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


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


Is the name of the second source scalable vector register Z0-Z7, encoded in the "Zm" field.


Is the immediate index, in the range 0 to 7, encoded in the "i3h:i3l" fields.


integer elements = VL DIV esize;
integer eltspersegment = 128 DIV esize;
bits(VL) operand1 = Z[n];
bits(VL) operand2 = Z[m];
bits(VL) operand3 = Z[da];
bits(VL) result;

for e = 0 to elements-1
    integer segmentbase = e - e MOD eltspersegment;
    integer s = 2 * segmentbase + index;
    bits(esize DIV 2) element1 = Elem[operand1, 2 * e + 1, esize DIV 2];
    bits(esize DIV 2) element2 = Elem[operand2, s, esize DIV 2];
    bits(esize) element3 = Elem[operand3, e, esize];
    if op1_neg then element1 = FPNeg(element1);
    Elem[result, e, esize] = FPMulAddH(element3, element1, element2, FPCR);

Z[da] = result;

Operational information

This instruction might be immediately preceded in program order by a MOVPRFX instruction. The MOVPRFX instruction must conform to all of the following requirements, otherwise the behavior of the MOVPRFX and this instruction is unpredictable:

  • The MOVPRFX instruction must be unpredicated.
  • 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.