FEXPA
Floating-point exponential accelerator
The FEXPA instruction accelerates the polynomial series calculation of the exp(x) function.
The double-precision variant copies the low 52 bits of an entry from a hard-wired table of 64-bit coefficients, indexed by the low 6 bits of each element of the source vector, and prepends to that the next 11 bits of the source element (src<16:6>), setting the sign bit to zero.
The single-precision variant copies the low 23 bits of an entry from hard-wired table of 32-bit coefficients, indexed by the low 6 bits of each element of the source vector, and prepends to that the next 8 bits of the source element (src<13:6>), setting the sign bit to zero.
The half-precision variant copies the low 10 bits of an entry from hard-wired table of 16-bit coefficients, indexed by the low 5 bits of each element of the source vector, and prepends to that the next 5 bits of the source element (src<9:5>), setting the sign bit to zero.
A coefficient table entry with index m holds the floating-point value 2(m/64), or for the half-precision variant 2(m/32). This instruction is unpredicated.
This instruction is illegal when executed in Streaming SVE mode, unless FEAT_SME_FA64 is implemented and enabled.
Green
False
SM_0_only
0
0
0
0
0
1
0
0
1
0
0
0
0
0
1
0
1
1
1
0
FEXPA <Zd>.<T>, <Zn>.<T>
if !IsFeatureImplemented(FEAT_SVE) then UNDEFINED;
if size == '00' then UNDEFINED;
constant integer esize = 8 << UInt(size);
constant integer n = UInt(Zn);
constant integer d = UInt(Zd);
<Zd>
Is the name of the destination scalable vector register, encoded in the "Zd" field.
<T>
Is the size specifier,
size
<T>
00
RESERVED
01
H
10
S
11
D
<Zn>
Is the name of the source scalable vector register, encoded in the "Zn" field.
CheckNonStreamingSVEEnabled();
constant integer VL = CurrentVL;
constant integer PL = VL DIV 8;
constant integer elements = VL DIV esize;
constant bits(VL) operand = Z[n, VL];
bits(VL) result;
for e = 0 to elements-1
constant bits(esize) element = Elem[operand, e, esize];
Elem[result, e, esize] = FPExpA(element);
Z[d, VL] = result;