SQDMULH (by element)

Signed saturating Doubling Multiply returning High half (by element). This instruction multiplies each vector element in the first source SIMD&FP register by the specified vector element of the second source SIMD&FP register, doubles the results, places the most significant half of the final results into a vector, and writes the vector to the destination SIMD&FP register.

The results are truncated. For rounded results, see SQRDMULH.

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: Scalar and Vector

Scalar

313029282726252423222120191817161514131211109876543210
01011111sizeLMRm1100H0RnRd
Uop

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

constant integer idxdsize = 64 << UInt(H); integer index; bit Rmhi; case size of when '01' index = UInt(H:L:M); Rmhi = '0'; when '10' index = UInt(H:L); Rmhi = M; otherwise UNDEFINED; integer d = UInt(Rd); integer n = UInt(Rn); integer m = UInt(Rmhi:Rm); constant integer esize = 8 << UInt(size); constant integer datasize = esize; integer elements = 1; boolean round = (op == '1');

Vector

313029282726252423222120191817161514131211109876543210
0Q001111sizeLMRm1100H0RnRd
Uop

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

constant integer idxdsize = 64 << UInt(H); integer index; bit Rmhi; case size of when '01' index = UInt(H:L:M); Rmhi = '0'; when '10' index = UInt(H:L); Rmhi = M; otherwise UNDEFINED; integer d = UInt(Rd); integer n = UInt(Rn); integer m = UInt(Rmhi:Rm); constant integer esize = 8 << UInt(size); constant integer datasize = 64 << UInt(Q); integer elements = datasize DIV esize; boolean round = (op == '1');

Assembler Symbols

<V>

Is a width specifier, encoded in size:

size <V>
00 RESERVED
01 H
10 S
11 RESERVED
<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.

<Vm>

Is the name of the second SIMD&FP source register, encoded in size:M:Rm:

size <Vm>
00 RESERVED
01 UInt('0':Rm)
10 UInt(M:Rm)
11 RESERVED
Restricted to V0-V15 when element size <Ts> is H.
<Ts>

Is an element size specifier, encoded in size:

size <Ts>
00 RESERVED
01 H
10 S
11 RESERVED
<index>

Is the element index, encoded in size:H:L:M:

size <index>
00 RESERVED
01 UInt(H:L:M)
10 UInt(H:L)
11 RESERVED
<Vd>

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

<T>

Is an arrangement specifier, encoded in size:Q:

size Q <T>
00 x RESERVED
01 0 4H
01 1 8H
10 0 2S
10 1 4S
11 x RESERVED
<Vn>

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

Operation

CheckFPAdvSIMDEnabled64(); bits(datasize) operand1 = V[n, datasize]; bits(idxdsize) operand2 = V[m, idxdsize]; bits(datasize) result; integer element1; integer element2; integer product; boolean sat; element2 = SInt(Elem[operand2, index, esize]); for e = 0 to elements-1 element1 = SInt(Elem[operand1, e, esize]); product = 2 * element1 * element2; product = RShr(product, esize, round); // The following only saturates if element1 and element2 equal -(2^(esize-1)) (Elem[result, e, esize], sat) = SignedSatQ(product, esize); if sat then FPSR.QC = '1'; V[d, datasize] = result;

Operational information

If PSTATE.DIT is 1:


Internal version only: aarchmrs v2024-03_relA, pseudocode v2024-03_rel, sve v2024-03_rel ; Build timestamp: 2024-03-26T09:45

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