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FCVT

Floating-point convert precision (predicated).

Convert the size and precision of each active floating-point element of the source vector, and place the results in the corresponding elements of the destination vector. Inactive elements in the destination vector register remain unmodified.

Since the input and result types have a different size the smaller type is held unpacked in the least significant bits of elements of the larger size. When the input is the smaller type the upper bits of each source element are ignored. When the result is the smaller type the upper bits of each destination element are set to zero.

It has encodings from 6 classes: Half-precision to single-precision , Half-precision to double-precision , Single-precision to half-precision , Single-precision to double-precision , Double-precision to half-precision and Double-precision to single-precision

Half-precision to single-precision

313029282726252423222120191817161514131211109876543210
0110010110001001101PgZnZd

Half-precision to single-precision

FCVT <Zd>.S, <Pg>/M, <Zn>.H

if !HaveSVE() then UNDEFINED;
integer esize = 32;
integer g = UInt(Pg);
integer n = UInt(Zn);
integer d = UInt(Zd);
integer s_esize = 16;
integer d_esize = 32;

Half-precision to double-precision

313029282726252423222120191817161514131211109876543210
0110010111001001101PgZnZd

Half-precision to double-precision

FCVT <Zd>.D, <Pg>/M, <Zn>.H

if !HaveSVE() then UNDEFINED;
integer esize = 64;
integer g = UInt(Pg);
integer n = UInt(Zn);
integer d = UInt(Zd);
integer s_esize = 16;
integer d_esize = 64;

Single-precision to half-precision

313029282726252423222120191817161514131211109876543210
0110010110001000101PgZnZd

Single-precision to half-precision

FCVT <Zd>.H, <Pg>/M, <Zn>.S

if !HaveSVE() then UNDEFINED;
integer esize = 32;
integer g = UInt(Pg);
integer n = UInt(Zn);
integer d = UInt(Zd);
integer s_esize = 32;
integer d_esize = 16;

Single-precision to double-precision

313029282726252423222120191817161514131211109876543210
0110010111001011101PgZnZd

Single-precision to double-precision

FCVT <Zd>.D, <Pg>/M, <Zn>.S

if !HaveSVE() then UNDEFINED;
integer esize = 64;
integer g = UInt(Pg);
integer n = UInt(Zn);
integer d = UInt(Zd);
integer s_esize = 32;
integer d_esize = 64;

Double-precision to half-precision

313029282726252423222120191817161514131211109876543210
0110010111001000101PgZnZd

Double-precision to half-precision

FCVT <Zd>.H, <Pg>/M, <Zn>.D

if !HaveSVE() then UNDEFINED;
integer esize = 64;
integer g = UInt(Pg);
integer n = UInt(Zn);
integer d = UInt(Zd);
integer s_esize = 64;
integer d_esize = 16;

Double-precision to single-precision

313029282726252423222120191817161514131211109876543210
0110010111001010101PgZnZd

Double-precision to single-precision

FCVT <Zd>.S, <Pg>/M, <Zn>.D

if !HaveSVE() then UNDEFINED;
integer esize = 64;
integer g = UInt(Pg);
integer n = UInt(Zn);
integer d = UInt(Zd);
integer s_esize = 64;
integer d_esize = 32;

Assembler Symbols

<Zd>

Is the name of the destination scalable vector register, encoded in the "Zd" field.

<Pg>

Is the name of the governing scalable predicate register P0-P7, encoded in the "Pg" field.

<Zn>

Is the name of the source scalable vector register, encoded in the "Zn" field.

Operation

CheckSVEEnabled();
integer elements = VL DIV esize;
bits(PL) mask = P[g];
bits(VL) operand  = Z[n];
bits(VL) result = Z[d];

for e = 0 to elements-1
    bits(esize) element = Elem[operand, e, esize];
    if ElemP[mask, e, esize] == '1' then
        bits(d_esize) res = FPConvertSVE(element<s_esize-1:0>, FPCR);
        Elem[result, e, esize] = ZeroExtend(res);

Z[d] = result;

Operational information

This instruction might be immediately preceded in program order by a MOVPRFX instruction that conforms to all of the following requirements, otherwise the behavior of either or both instructions is unpredictable:

  • The MOVPRFX instruction 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.
The MOVPRFX instructions that can be used with this instruction are as follows:
  • An unpredicated MOVPRFX instruction.
  • A predicated MOVPRFX instruction using the same governing predicate register and source element size as this instruction.