Arm® A32/T32 Instruction Set Architecture: Armv8, for Armv8-A architecture profile Documentation

VSQRT

Square Root calculates the square root of the value in a floating-point register and writes the result to another floating-point register.

Depending on settings in the CPACR, NSACR, HCPTR, and FPEXC 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.

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

A1

if size == '00' || (size == '01' && !HaveFP16Ext()) then UNDEFINED;
if size == '01' && cond != '1110' then UNPREDICTABLE;
if FPSCR.Len != '000' || FPSCR.Stride != '00' then UNDEFINED;
case size of
    when '01' esize = 16; d = UInt(Vd:D); m = UInt(Vm:M);
    when '10' esize = 32; d = UInt(Vd:D); m = UInt(Vm:M);
    when '11' esize = 64; d = UInt(D:Vd); m = UInt(M:Vm);

CONSTRAINED UNPREDICTABLE behavior

If size == '01' && cond != '1110', then one of the following behaviors must occur:

• The instruction is undefined.
• The instruction executes as if it passes the Condition code check.
• The instruction executes as NOP. This means it behaves as if it fails the Condition code check.

T1

if size == '00' || (size == '01' && !HaveFP16Ext()) then UNDEFINED;
if size == '01' && InITBlock()  then UNPREDICTABLE;
if FPSCR.Len != '000' || FPSCR.Stride != '00' then UNDEFINED;
case size of
    when '01' esize = 16; d = UInt(Vd:D); m = UInt(Vm:M);
    when '10' esize = 32; d = UInt(Vd:D); m = UInt(Vm:M);
    when '11' esize = 64; d = UInt(D:Vd); m = UInt(M:Vm);

CONSTRAINED UNPREDICTABLE behavior

If size == '01' && InITBlock(), then one of the following behaviors must occur:

• The instruction is undefined.
• The instruction executes as if it passes the Condition code check.
• The instruction executes as NOP. This means it behaves as if it fails the Condition code check.

Assembler Symbols

if ConditionPassed() then
    EncodingSpecificOperations();  CheckVFPEnabled(TRUE);
    case esize of
        when 16 S[d] = Zeros(16) : FPSqrt(S[m]<15:0>, FPSCR);
        when 32 S[d] = FPSqrt(S[m], FPSCR);
        when 64 D[d] = FPSqrt(D[m], FPSCR);