SSHL

Signed Shift Left (register). This instruction takes each signed integer value in the vector of the first source SIMD&FP register, shifts each value by a value from the least significant byte of the corresponding element of the second source SIMD&FP register, places the results in a vector, and writes the vector to the destination SIMD&FP register.

If the shift value is positive, the operation is a left shift. If the shift value is negative, it is a truncating right shift. For a rounding shift, see SRSHL.

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
01011110size1Rm010001RnRd
URS

SSHL <V><d>, <V><n>, <V><m>

integer d = UInt(Rd); integer n = UInt(Rn); integer m = UInt(Rm); integer esize = 8 << UInt(size); integer datasize = esize; integer elements = 1; boolean unsigned = (U == '1'); boolean rounding = (R == '1'); boolean saturating = (S == '1'); if S == '0' && size != '11' then UNDEFINED;

Vector

313029282726252423222120191817161514131211109876543210
0Q001110size1Rm010001RnRd
URS

SSHL <Vd>.<T>, <Vn>.<T>, <Vm>.<T>

integer d = UInt(Rd); integer n = UInt(Rn); integer m = UInt(Rm); if size:Q == '110' then UNDEFINED; integer esize = 8 << UInt(size); integer datasize = if Q == '1' then 128 else 64; integer elements = datasize DIV esize; boolean unsigned = (U == '1'); boolean rounding = (R == '1'); boolean saturating = (S == '1');

Assembler Symbols

<V>

Is a width specifier, encoded in size:

size <V>
0x RESERVED
10 RESERVED
11 D
<d>

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

<n>

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

<m>

Is the number of the second SIMD&FP source register, encoded in the "Rm" field.

<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 0 8B
00 1 16B
01 0 4H
01 1 8H
10 0 2S
10 1 4S
11 0 RESERVED
11 1 2D
<Vn>

Is the name 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 the "Rm" field.

Operation

CheckFPAdvSIMDEnabled64(); bits(datasize) operand1 = V[n]; bits(datasize) operand2 = V[m]; bits(datasize) result; integer round_const = 0; integer shift; integer element; boolean sat; for e = 0 to elements-1 shift = SInt(Elem[operand2, e, esize]<7:0>); if rounding then round_const = 1 << (-shift - 1); // 0 for left shift, 2^(n-1) for right shift element = (Int(Elem[operand1, e, esize], unsigned) + round_const) << shift; if saturating then (Elem[result, e, esize], sat) = SatQ(element, esize, unsigned); if sat then FPSR.QC = '1'; else Elem[result, e, esize] = element<esize-1:0>; V[d] = result;

Operational information

If PSTATE.DIT is 1:


Internal version only: isa v33.11seprel, AdvSIMD v29.05, pseudocode v2021-09_rel, sve v2021-09_rc3d ; Build timestamp: 2021-10-06T11:41

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