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BFMLALT (vectors)

BFloat16 floating-point multiply-add long to single-precision (top).

This BFloat16 floating-point multiply-add long instruction widens the odd-numbered 16-bit BFloat16 elements in the first source vector and the corresponding elements 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.

Unlike the BFloat16 matrix multiplication and dot product instructions, this instruction performs a fused multiply-add that honors all of the FPCR bits that apply to single-precision arithmetic. It can also generate a floating-point exception that causes cumulative exception bits in the FPSR to be set, or a synchronous exception to be taken, depending on the enable bits in the FPCR.

ID_AA64ZFR0_EL1.BF16 indicates whether this instruction is implemented.



BFMLALT <Zda>.S, <Zn>.H, <Zm>.H

if !HaveSVE() || !HaveBF16Ext() then UNDEFINED;
integer n = UInt(Zn);
integer m = UInt(Zm);
integer da = UInt(Zda);

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, encoded in the "Zm" field.


integer elements = VL DIV 32;
bits(VL) operand1 = Z[n];
bits(VL) operand2 = Z[m];
bits(VL) operand3 = Z[da];
bits(VL) result;

for e = 0 to elements-1
    bits(32) element1 = Elem[operand1, 2 * e + 1, 16] : Zeros(16);
    bits(32) element2 = Elem[operand2, 2 * e + 1, 16] : Zeros(16);
    bits(32) element3 = Elem[operand3, e, 32];
    Elem[result, e, 32] = 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.