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FMUL (immediate)

Floating-point multiply by immediate (predicated).

Multiply by an immediate each active floating-point element of the source vector, and destructively place the results in the corresponding elements of the source vector. The immediate may take the value +0.5 or +2.0 only. Inactive elements in the destination vector register remain unmodified.



FMUL <Zdn>.<T>, <Pg>/M, <Zdn>.<T>, <const>

if !HaveSVE() then UNDEFINED;
if size == '00' then UNDEFINED;
integer esize = 8 << UInt(size);
integer g = UInt(Pg);
integer dn = UInt(Zdn);
bits(esize) imm = if i1 == '0' then FPPointFive('0') else FPTwo('0');

Assembler Symbols


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

<T> Is the size specifier, encoded in size:
size <T>
01 H
10 S
11 D

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

<const> Is the floating-point immediate value, encoded in i1:
i1 <const>
0 #0.5
1 #2.0


integer elements = VL DIV esize;
bits(PL) mask = P[g];
bits(VL) operand1 = Z[dn];
bits(VL) result;

for e = 0 to elements-1
    bits(esize) element1 = Elem[operand1, e, esize];
    if ElemP[mask, e, esize] == '1' then
        Elem[result, e, esize] = FPMul(element1, imm, FPCR<31:0>);
        Elem[result, e, esize] = element1;

Z[dn] = 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, or be predicated using the same governing predicate register and source element size as this instruction.
  • 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.