Base Instructions | SIMD&FP Instructions | SVE Instructions | SME Instructions | Index by Encoding | Shared Pseudocode | Proprietary Notice

## FMUL (by element)

Floating-point Multiply (by element). This instruction multiplies the vector elements in the first source SIMD&FP register by the specified value in the second source SIMD&FP register, places the results in a vector, and writes the vector to the destination SIMD&FP register. All the values in this instruction are floating-point values.

This instruction can generate a floating-point exception. Depending on the settings in FPCR, the exception results in either a flag being set in FPSR or a synchronous exception being generated. For more information, see Floating-point exception traps.

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 4 classes: Scalar, half-precision , Scalar, single-precision and double-precision , Vector, half-precision and Vector, single-precision and double-precision

### Scalar, half-precision
(FEAT_FP16)

31 | 30 | 29 | 28 | 27 | 26 | 25 | 24 | 23 | 22 | 21 | 20 | 19 | 18 | 17 | 16 | 15 | 14 | 13 | 12 | 11 | 10 | 9 | 8 | 7 | 6 | 5 | 4 | 3 | 2 | 1 | 0
0 | 1 | 0 | 1 | 1 | 1 | 1 | 1 | 0 | 0 | L | M | Rm | 1 | 0 | 0 | 1 | H | 0 | Rn | Rd
| U |  |  |  |  |  |  |  |  |  |

####

FMUL <Hd>, <Hn>, <Vm>.H[<index>]

if !IsFeatureImplemented(FEAT_FP16) then UNDEFINED; constant integer idxdsize = 64 << UInt(H); integer n = UInt(Rn); integer m = UInt(Rm); integer d = UInt(Rd); integer index = UInt(H:L:M); constant integer esize = 16; constant integer datasize = esize; integer elements = 1; boolean mulx_op = (U == '1');

### Scalar, single-precision and double-precision

31 | 30 | 29 | 28 | 27 | 26 | 25 | 24 | 23 | 22 | 21 | 20 | 19 | 18 | 17 | 16 | 15 | 14 | 13 | 12 | 11 | 10 | 9 | 8 | 7 | 6 | 5 | 4 | 3 | 2 | 1 | 0
0 | 1 | 0 | 1 | 1 | 1 | 1 | 1 | 1 | sz | L | M | Rm | 1 | 0 | 0 | 1 | H | 0 | Rn | Rd
| U |  |  |  |  |  |  |  |  |  |  |

####

FMUL <V><d>, <V><n>, <Vm>.<Ts>[<index>]

constant integer idxdsize = 64 << UInt(H); integer index; bit Rmhi = M; case sz:L of when '0x' index = UInt(H:L); when '10' index = UInt(H); when '11' UNDEFINED; integer d = UInt(Rd); integer n = UInt(Rn); integer m = UInt(Rmhi:Rm); constant integer esize = 32 << UInt(sz); constant integer datasize = esize; integer elements = 1; boolean mulx_op = (U == '1');

### Vector, half-precision
(FEAT_FP16)

31 | 30 | 29 | 28 | 27 | 26 | 25 | 24 | 23 | 22 | 21 | 20 | 19 | 18 | 17 | 16 | 15 | 14 | 13 | 12 | 11 | 10 | 9 | 8 | 7 | 6 | 5 | 4 | 3 | 2 | 1 | 0
0 | Q | 0 | 0 | 1 | 1 | 1 | 1 | 0 | 0 | L | M | Rm | 1 | 0 | 0 | 1 | H | 0 | Rn | Rd
|  | U |  |  |  |  |  |  |  |  |  |

####

FMUL <Vd>.<T>, <Vn>.<T>, <Vm>.H[<index>]

if !IsFeatureImplemented(FEAT_FP16) then UNDEFINED; constant integer idxdsize = 64 << UInt(H); integer n = UInt(Rn); integer m = UInt(Rm); integer d = UInt(Rd); integer index = UInt(H:L:M); constant integer esize = 16; constant integer datasize = 64 << UInt(Q); integer elements = datasize DIV esize; boolean mulx_op = (U == '1');

### Vector, single-precision and double-precision

31 | 30 | 29 | 28 | 27 | 26 | 25 | 24 | 23 | 22 | 21 | 20 | 19 | 18 | 17 | 16 | 15 | 14 | 13 | 12 | 11 | 10 | 9 | 8 | 7 | 6 | 5 | 4 | 3 | 2 | 1 | 0
0 | Q | 0 | 0 | 1 | 1 | 1 | 1 | 1 | sz | L | M | Rm | 1 | 0 | 0 | 1 | H | 0 | Rn | Rd
|  | U |  |  |  |  |  |  |  |  |  |  |

####

FMUL <Vd>.<T>, <Vn>.<T>, <Vm>.<Ts>[<index>]

constant integer idxdsize = 64 << UInt(H); integer index; bit Rmhi = M; case sz:L of when '0x' index = UInt(H:L); when '10' index = UInt(H); when '11' UNDEFINED; integer d = UInt(Rd); integer n = UInt(Rn); integer m = UInt(Rmhi:Rm); if sz:Q == '10' then UNDEFINED; constant integer esize = 32 << UInt(sz); constant integer datasize = 64 << UInt(Q); integer elements = datasize DIV esize; boolean mulx_op = (U == '1');

### Assembler Symbols

<Hd> | Is the 16-bit name of the SIMD&FP destination register, encoded in the "Rd" field.

<Hn> | Is the 16-bit name of the first SIMD&FP source register, encoded in the "Rn" field.

<V> | Is a width specifier, encoded in sz:
sz | <V>
--- | ---
0 | S
1 | D

<d> | Is the number of the SIMD&FP destination register, encoded in the "Rd" field.

<n> | Is the number of the first SIMD&FP source register, encoded in the "Rn" field.

<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 and double-precision variant: is an arrangement specifier, encoded in Q:sz:
Q | sz | <T>
--- | --- | ---
0 | 0 | 2S
0 | 1 | RESERVED
1 | 0 | 4S
1 | 1 | 2D

<Vn> | Is the name of the first SIMD&FP source register, encoded in the "Rn" field.

<Vm> | For the half-precision variant: is the name of the second SIMD&FP source register, in the range V0 to V15, encoded in the "Rm" field.
| For the single-precision and double-precision variant: is the name of the second SIMD&FP source register, encoded in the "M:Rm" fields.

<Ts> | Is an element size specifier, encoded in sz:
sz | <Ts>
--- | ---
0 | S
1 | D

<index> | For the half-precision variant: is the element index, in the range 0 to 7, encoded in the "H:L:M" fields.
| For the single-precision and double-precision variant: is the element index, encoded in sz:L:H:
sz | L | <index>
--- | --- | ---
0 | x | H:L
1 | 0 | H
1 | 1 | RESERVED

### Operation

CheckFPAdvSIMDEnabled64(); bits(datasize) operand1 = V[n, datasize]; bits(idxdsize) operand2 = V[m, idxdsize]; bits(esize) element1; bits(esize) element2 = Elem[operand2, index, esize]; boolean merge = elements == 1 && IsMerging(FPCR); bits(128) result = if merge then V[n, 128] else Zeros(128); for e = 0 to elements-1 element1 = Elem[operand1, e, esize]; if mulx_op then Elem[result, e, esize] = FPMulX(element1, element2, FPCR); else Elem[result, e, esize] = FPMul(element1, element2, FPCR); V[d, 128] = result;

Base Instructions | SIMD&FP Instructions | SVE Instructions | SME Instructions | Index by Encoding | Shared Pseudocode | Proprietary Notice

Internal version only: isa v33.74, AdvSIMD v29.23, pseudocode v2023-09_rel, sve v2023-09_rc3 ; Build timestamp: 2023-09-27T17:06

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