SRSRA

Signed rounding shift right and accumulate (immediate)

Shift right by immediate each signed element of the source vector, preserving the sign bit, and add the rounded intermediate result destructively to the corresponding elements of the addend vector. The immediate shift amount is an unsigned value in the range 1 to number of bits per element. This instruction is unpredicated.

Encoding: SVE2

Variants: FEAT_SVE2 || FEAT_SME (FEAT_SVE2 || FEAT_SME)

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	0	0	1	0	1			0						1	1	1	0	1	0
								tszh			tszl		imm3							R	U	Zn					Zda

SRSRA <Zda>.<T>, <Zn>.<T>, #<const>

Decoding algorithm

if !IsFeatureImplemented(FEAT_SVE2) && !IsFeatureImplemented(FEAT_SME) then
    EndOfDecode(Decode_UNDEF);
constant bits(4) tsize = tszh:tszl;
if tsize == '0000' then EndOfDecode(Decode_UNDEF);
constant integer esize = 8 << HighestSetBit(tsize);
constant integer n = UInt(Zn);
constant integer da = UInt(Zda);
constant integer shift = (2 * esize) - UInt(tsize:imm3);

Operation

CheckSVEEnabled();
constant integer VL = CurrentVL;
constant integer elements = VL DIV esize;
constant bits(VL) operand1 = Z[n, VL];
constant bits(VL) operand2 = Z[da, VL];
bits(VL) result;

for e = 0 to elements-1
    constant integer element = (SInt(Elem[operand1, e, esize]) + (1 << (shift - 1))) >> shift;
    Elem[result, e, esize] = Elem[operand2, e, esize] + element;

Z[da, VL] = result;

Explanations

<Zda>: Is the name of the third source and destination scalable vector register, encoded in the "Zda" field.
<T>: <Zn>: Is the name of the first source scalable vector register, encoded in the "Zn" field.
<const>: Is the immediate shift amount, in the range 1 to number of bits per element, encoded in "tszh:tszl:imm3".

Operational Notes

This instruction might be immediately preceded in program order by a MOVPRFX instruction. The MOVPRFX must conform to all of the following requirements, otherwise the behavior of the MOVPRFX and this instruction is CONSTRAINED UNPREDICTABLE:

• The MOVPRFX must be unpredicated.
• The MOVPRFX must specify the same destination register as this instruction.
• The destination register must not refer to architectural register state referenced by any other source operand register of this instruction.