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

VCVT (integer to floating-point, floating-point)

Convert integer to floating-point converts a 32-bit integer to floating-point using the rounding mode specified by the FPSCR, and places the result in a second register.

VCVT (between floating-point and fixed-point, floating-point) describes conversions between floating-point and 16-bit integers.

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 opc2 != '000' && opc2 != '10x' then SEE "Related encodings";
if size == '00' || (size == '01' && !HaveFP16Ext()) then UNDEFINED;
if size == '01' && cond != '1110' then UNPREDICTABLE;
to_integer = (opc2<2> == '1');
if to_integer then
    unsigned = (opc2<0> == '0');
    rounding = if op == '1' then FPRounding_ZERO else FPRoundingMode(FPSCR);
    d = UInt(Vd:D);
    case size of
        when '01' esize = 16; m = UInt(Vm:M);
        when '10' esize = 32; m = UInt(Vm:M);
        when '11' esize = 64; m = UInt(M:Vm);
else
    unsigned = (op == '0');
    rounding = FPRoundingMode(FPSCR);
    m = UInt(Vm:M);
    case size of
        when '01' esize = 16; d = UInt(Vd:D);
        when '10' esize = 32; d = UInt(Vd:D);
        when '11' esize = 64; d = UInt(D:Vd);

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 opc2 != '000' && opc2 != '10x' then SEE "Related encodings";
if size == '00' || (size == '01' && !HaveFP16Ext()) then UNDEFINED;
if size == '01' && InITBlock()  then UNPREDICTABLE;
to_integer = (opc2<2> == '1');
if to_integer then
    unsigned = (opc2<0> == '0');
    rounding = if op == '1' then FPRounding_ZERO else FPRoundingMode(FPSCR);
    d = UInt(Vd:D);
    case size of
        when '01' esize = 16; m = UInt(Vm:M);
        when '10' esize = 32; m = UInt(Vm:M);
        when '11' esize = 64; m = UInt(M:Vm);
else
    unsigned = (op == '0');
    rounding = FPRoundingMode(FPSCR);
    m = UInt(Vm:M);
    case size of
        when '01' esize = 16; d = UInt(Vd:D);
        when '10' esize = 32; d = UInt(Vd:D);
        when '11' esize = 64; d = UInt(D:Vd);

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.

Related encodings: See Floating-point data-processing for the T32 instruction set, or Floating-point data-processing for the A32 instruction set.

Assembler Symbols

if ConditionPassed() then
    EncodingSpecificOperations();  CheckVFPEnabled(TRUE);
    if to_integer then
        case esize of
            when 16
                S[d] = FPToFixed(S[m]<15:0>, 0, unsigned, FPSCR, rounding);
            when 32
                S[d] = FPToFixed(S[m], 0, unsigned, FPSCR, rounding);
            when 64
                S[d] = FPToFixed(D[m], 0, unsigned, FPSCR, rounding);
    else
        case esize of
            when 16
                bits(16) fp16 = FixedToFP(S[m], 0, unsigned, FPSCR, rounding);
                S[d] = Zeros(16):fp16;
            when 32
                S[d] = FixedToFP(S[m], 0, unsigned, FPSCR, rounding);
            when 64
                D[d] = FixedToFP(S[m], 0, unsigned, FPSCR, rounding);