You copied the Doc URL to your clipboard.

SSAT

Signed Saturate saturates an optionally-shifted signed value to a selectable signed range.

This instruction sets PSTATE.Q to 1 if the operation saturates.

It has encodings from the following instruction sets: A32 ( A1 ) and T32 ( T1 ) .

A1

313029282726252423222120191817161514131211109876543210
!= 11110110101sat_immRdimm5sh01Rn
cond

Arithmetic shift right (sh == 1)

SSAT{<c>}{<q>} <Rd>, #<imm>, <Rn>, ASR #<amount>

Logical shift left (sh == 0)

SSAT{<c>}{<q>} <Rd>, #<imm>, <Rn> {, LSL #<amount>}

d = UInt(Rd);  n = UInt(Rn);  saturate_to = UInt(sat_imm)+1;
(shift_t, shift_n) = DecodeImmShift(sh:'0', imm5);
if d == 15 || n == 15 then UNPREDICTABLE;

T1

15141312111098765432101514131211109876543210
11110(0)1100sh0Rn0imm3Rdimm2(0)sat_imm

Arithmetic shift right (sh == 1 && !(imm3 == 000 && imm2 == 00))

SSAT{<c>}{<q>} <Rd>, #<imm>, <Rn>, ASR #<amount>

Logical shift left (sh == 0)

SSAT{<c>}{<q>} <Rd>, #<imm>, <Rn> {, LSL #<amount>}

if sh == '1' && (imm3:imm2) == '00000' then SEE "SSAT16";
d = UInt(Rd);  n = UInt(Rn);  saturate_to = UInt(sat_imm)+1;
(shift_t, shift_n) = DecodeImmShift(sh:'0', imm3:imm2);
if d == 15 || n == 15 then UNPREDICTABLE; // Armv8-A removes UNPREDICTABLE for R13

For more information about the constrained unpredictable behavior of this instruction, see Architectural Constraints on UNPREDICTABLE behaviors.

Assembler Symbols

<c>

See Standard assembler syntax fields.

<q>

See Standard assembler syntax fields.

<Rd>

Is the general-purpose destination register, encoded in the "Rd" field.

<imm>

Is the bit position for saturation, in the range 1 to 32, encoded in the "sat_imm" field as <imm>-1.

<Rn>

Is the general-purpose source register, encoded in the "Rn" field.

<amount>

For encoding A1: is the optional shift amount, in the range 0 to 31, defaulting to 0 and encoded in the "imm5" field.

For encoding A1: is the shift amount, in the range 1 to 32 encoded in the "imm5" field as <amount> modulo 32.

For encoding T1: is the optional shift amount, in the range 0 to 31, defaulting to 0 and encoded in the "imm3:imm2" field.

For encoding T1: is the shift amount, in the range 1 to 31 encoded in the "imm3:imm2" field as <amount>.

Operation

if ConditionPassed() then
    EncodingSpecificOperations();
    operand = Shift(R[n], shift_t, shift_n, PSTATE.C);  // PSTATE.C ignored
    (result, sat) = SignedSatQ(SInt(operand), saturate_to);
    R[d] = SignExtend(result, 32);
    if sat then
        PSTATE.Q = '1';
Was this page helpful? Yes No