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PRFW (vector plus immediate)

Gather prefetch words (vector plus immediate).

Gather prefetch of words from the active memory addresses generated by a vector base plus immediate index. The index is a multiple of 4 in the range 0 to 124. Inactive addresses are not prefetched from memory.

The <prfop> symbol specifies the prefetch hint as a combination of three options: access type PLD for load or PST for store; target cache level L1, L2 or L3; temporality (KEEP for temporal or STRM for non-temporal).

It has encodings from 2 classes: 32-bit element and 64-bit element

32-bit element

313029282726252423222120191817161514131211109876543210
10000101000imm5111PgZn0prfop
msz<1>msz<0>

PRFW <prfop>, <Pg>, [<Zn>.S{, #<imm>}]

if !HaveSVE() then UNDEFINED;
integer esize = 32;
integer g = UInt(Pg);
integer n = UInt(Zn);
integer level = UInt(prfop<2:1>);
boolean stream = (prfop<0> == '1');
pref_hint = if prfop<3> == '0' then Prefetch_READ else Prefetch_WRITE;
integer scale = 2;
integer offset = UInt(imm5);

64-bit element

313029282726252423222120191817161514131211109876543210
11000101000imm5111PgZn0prfop
msz<1>msz<0>

PRFW <prfop>, <Pg>, [<Zn>.D{, #<imm>}]

if !HaveSVE() then UNDEFINED;
integer esize = 64;
integer g = UInt(Pg);
integer n = UInt(Zn);
integer level = UInt(prfop<2:1>);
boolean stream = (prfop<0> == '1');
pref_hint = if prfop<3> == '0' then Prefetch_READ else Prefetch_WRITE;
integer scale = 2;
integer offset = UInt(imm5);

Assembler Symbols

<prfop> Is the prefetch operation specifier, encoded in prfop:
prfop <prfop>
0000 PLDL1KEEP
0001 PLDL1STRM
0010 PLDL2KEEP
0011 PLDL2STRM
0100 PLDL3KEEP
0101 PLDL3STRM
x11x #uimm4
1000 PSTL1KEEP
1001 PSTL1STRM
1010 PSTL2KEEP
1011 PSTL2STRM
1100 PSTL3KEEP
1101 PSTL3STRM
<Pg>

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

<Zn>

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

<imm>

Is the optional unsigned immediate byte offset, a multiple of 4 in the range 0 to 124, defaulting to 0, encoded in the "imm5" field.

Operation

CheckSVEEnabled();
integer elements = VL DIV esize;
bits(PL) mask = P[g];
bits(VL) base;
bits(64) addr;
base = Z[n];

for e = 0 to elements-1
    if ElemP[mask, e, esize] == '1' then
        addr = ZeroExtend(Elem[base, e, esize], 64) + (offset << scale);
        Hint_Prefetch(addr, pref_hint, level, stream);