VRSHRN
Vector Rounding Shift Right and Narrow
Vector Rounding Shift Right and Narrow takes each element in a vector, right shifts them by an immediate value, and places the rounded results in the destination vector. For truncated results, see VSHRN.
The operand elements can be 16-bit, 32-bit, or 64-bit integers. There is no distinction between signed and unsigned integers. The destination elements are half the size of the source elements.
Depending on settings in the CPACR, NSACR, and HCPTR registers, and the Security state and PE mode in which the instruction is executed, an attempt to execute the instruction might be undefined, or trapped to Hyp mode. For more information see Enabling Advanced SIMD and floating-point support.
Related encodings: See Advanced SIMD one register and modified immediate for the T32 instruction set, or Advanced SIMD one register and modified immediate for the A32 instruction set.
If CPSR.DIT is 1 and this instruction passes its condition execution check:
The execution time of this instruction is independent of:The values of the data supplied in any of its registers.The values of the NZCV flags.
The response of this instruction to asynchronous exceptions does not vary based on:The values of the data supplied in any of its registers.The values of the NZCV flags.
It has encodings from the following instruction sets:
A32 (
A1
)
and
T32 (
T1
)
.
1
1
1
1
0
0
1
0
1
1
0
0
0
0
1
1
Z
Z
Z
VRSHRN{<c>}{<q>}.I<size> <Dd>, <Qm>, #<imm>
if imm6 IN {'000xxx'} then SEE "Related encodings";
if Vm<0> == '1' then UNDEFINED;
integer esize;
integer elements;
integer shift_amount;
case imm6 of
when '001xxx' esize = 8; elements = 8; shift_amount = 16 - UInt(imm6);
when '01xxxx' esize = 16; elements = 4; shift_amount = 32 - UInt(imm6);
when '1xxxxx' esize = 32; elements = 2; shift_amount = 64 - UInt(imm6);
d = UInt(D:Vd); m = UInt(M:Vm);
1
1
1
0
1
1
1
1
1
1
0
0
0
0
1
1
Z
Z
Z
VRSHRN{<c>}{<q>}.I<size> <Dd>, <Qm>, #<imm>
if imm6 IN {'000xxx'} then SEE "Related encodings";
if Vm<0> == '1' then UNDEFINED;
integer esize;
integer elements;
integer shift_amount;
case imm6 of
when '001xxx' esize = 8; elements = 8; shift_amount = 16 - UInt(imm6);
when '01xxxx' esize = 16; elements = 4; shift_amount = 32 - UInt(imm6);
when '1xxxxx' esize = 32; elements = 2; shift_amount = 64 - UInt(imm6);
d = UInt(D:Vd); m = UInt(M:Vm);
<c>
For encoding A1: see Standard assembler syntax fields. This encoding must be unconditional.
<c>
For encoding T1: see Standard assembler syntax fields.
<q>
See Standard assembler syntax fields.
<size>
Is the data size for the elements of the vectors,
imm6<5:3>
<size>
001
16
01x
32
1xx
64
<Dd>
Is the 64-bit name of the SIMD&FP destination register, encoded in the "D:Vd" field.
<Qm>
Is the 128-bit name of the SIMD&FP source register, encoded in the "M:Vm" field as <Qm>*2.
<imm>
Is an immediate value, in the range 1 to <size>/2, encoded in the "imm6" field as <size>/2 - <imm>.
if ConditionPassed() then
EncodingSpecificOperations(); CheckAdvSIMDEnabled();
round_const = 1 << (shift_amount-1);
for e = 0 to elements-1
result = LSR(Elem[Qin[m>>1],e,2*esize] + round_const, shift_amount);
Elem[D[d],e,esize] = result<esize-1:0>;