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FMOV (vector, immediate)

Floating-point move immediate (vector). This instruction copies an immediate floating-point constant into every element of the SIMD&FP destination register.

Depending on the settings in the CPACR_EL1, CPTR_EL2, and CPTR_EL3 registers, and the current Security state and Exception level, an attempt to execute the instruction might be trapped.

It has encodings from 2 classes: Half-precision and Single-precision and double-precision

Half-precision
(Armv8.2)

313029282726252423222120191817161514131211109876543210
0Q00111100000abc111111defghRd

FMOV <Vd>.<T>, #<imm>

if !HaveFP16Ext() then UNDEFINED;

integer rd = UInt(Rd);

integer datasize = if Q == '1' then 128 else 64;
bits(datasize) imm;

imm8 = a:b:c:d:e:f:g:h;
imm16 = imm8<7>:NOT(imm8<6>):Replicate(imm8<6>, 2):imm8<5:0>:Zeros(6);

imm = Replicate(imm16, datasize DIV 16);

Single-precision and double-precision

313029282726252423222120191817161514131211109876543210
0Qop0111100000abc111101defghRd
cmode

Single-precision (op == 0)

FMOV <Vd>.<T>, #<imm>

Double-precision (Q == 1 && op == 1)

FMOV <Vd>.2D, #<imm>

integer rd = UInt(Rd);

integer datasize = if Q == '1' then 128 else 64;
bits(datasize) imm;
bits(64) imm64;

if cmode:op == '11111' then
    // FMOV Dn,#imm is in main FP instruction set
    if Q == '0' then UNDEFINED;

imm64 = AdvSIMDExpandImm(op, cmode, a:b:c:d:e:f:g:h);
imm = Replicate(imm64, datasize DIV 64);

Assembler Symbols

<Vd>

Is the name of the SIMD&FP destination register, encoded in the "Rd" field.

<T> For the half-precision variant: is an arrangement specifier, encoded in Q:
Q <T>
0 4H
1 8H
For the single-precision variant: is an arrangement specifier, encoded in Q:
Q <T>
0 2S
1 4S
<imm>

Is a signed floating-point constant with 3-bit exponent and normalized 4 bits of precision, encoded in "a:b:c:d:e:f:g:h". For details of the range of constants available and the encoding of <imm>, see Modified immediate constants in A64 floating-point instructions.

Operation

CheckFPAdvSIMDEnabled64();

V[rd] = imm;