USRA
Unsigned shift right and accumulate (immediate)
This instruction reads
each vector element in the source SIMD&FP register,
right shifts each result by an immediate value,
and accumulates the final results
with the vector elements of the destination SIMD&FP register.
All the values in this instruction are unsigned integer values.
The results are truncated. For rounded results, see
URSRA.
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.
If PSTATE.DIT is 1:
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 2 classes:
Scalar
and
Vector
0
1
1
1
1
1
1
1
0
1
x
x
x
0
0
0
1
0
1
USRA D<d>, D<n>, #<shift>
if immh<3> != '1' then UNDEFINED;
constant integer d = UInt(Rd);
constant integer n = UInt(Rn);
constant integer esize = 8 << 3;
constant integer datasize = esize;
constant integer elements = 1;
constant integer shift = (esize * 2) - UInt(immh:immb);
constant boolean unsigned = TRUE;
constant boolean round = FALSE;
0
1
0
1
1
1
1
0
!= 0000
0
0
0
1
0
1
USRA <Vd>.<T>, <Vn>.<T>, #<shift>
if immh == '0000' then SEE(asimdimm);
if immh<3>:Q == '10' then UNDEFINED;
constant integer d = UInt(Rd);
constant integer n = UInt(Rn);
constant integer esize = 8 << HighestSetBitNZ(immh);
constant integer datasize = 64 << UInt(Q);
constant integer elements = datasize DIV esize;
constant integer shift = (esize * 2) - UInt(immh:immb);
constant boolean unsigned = TRUE;
constant boolean round = FALSE;
<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.
<shift>
For the scalar variant: is the right shift amount, in the range 1 to 64, encoded as 128 - UInt("immh:immb").
<shift>
For the vector variant: is the right shift amount, in the range 1 to the element width in bits,
immh
<shift>
0001
16 - UInt(immh:immb)
001x
32 - UInt(immh:immb)
01xx
64 - UInt(immh:immb)
1xxx
128 - UInt(immh:immb)
<Vd>
Is the name of the SIMD&FP destination register, encoded in the "Rd" field.
<T>
Is an arrangement specifier,
immh
Q
<T>
0001
0
8B
0001
1
16B
001x
0
4H
001x
1
8H
01xx
0
2S
01xx
1
4S
1xxx
0
RESERVED
1xxx
1
2D
<Vn>
Is the name of the SIMD&FP source register, encoded in the "Rn" field.
CheckFPAdvSIMDEnabled64();
constant bits(datasize) operand = V[n, datasize];
constant bits(datasize) operand2 = V[d, datasize];
bits(datasize) result;
integer element;
for e = 0 to elements-1
element = RShr(Int(Elem[operand, e, esize], unsigned), shift, round);
Elem[result, e, esize] = Elem[operand2, e, esize] + element<esize-1:0>;
V[d, datasize] = result;