Arm® A64 Instruction Set Architecture: Armv8, for Armv8-A architecture profile

PTRUE, PTRUES

Initialise predicate from named constraint.

Set elements of the destination predicate to true if the element number satisfies the named predicate constraint, or to false otherwise. If the constraint specifies more elements than are available at the current vector length then all elements of the destination predicate are set to false.

The named predicate constraint limits the number of active elements in a single predicate to:

* A fixed number (VL1 to VL256)

* The largest power of two (POW2)

* The largest multiple of three or four (MUL3 or MUL4)

* All available, implicitly a multiple of two (ALL).

Unspecified or out of range constraint encodings generate an empty predicate or zero element count rather than Undefined Instruction exception. Optionally sets the First (N), None (Z), !Last (C) condition flags based on the predicate result, and the V flag to zero.

It has encodings from 2 classes: Not setting the condition flags and Setting the condition flags

Not setting the condition flags

if !HaveSVE() then UNDEFINED;
integer esize = 8 << UInt(size);
integer d = UInt(Pd);
boolean setflags = FALSE;
bits(5) pat = pattern;

Setting the condition flags

if !HaveSVE() then UNDEFINED;
integer esize = 8 << UInt(size);
integer d = UInt(Pd);
boolean setflags = TRUE;
bits(5) pat = pattern;

Assembler Symbols

CheckSVEEnabled();
integer elements = VL DIV esize;
integer count = DecodePredCount(pat, esize);
bits(PL) result;

for e = 0 to elements-1
    ElemP[result, e, esize] = if e < count then '1' else '0';

if setflags then
    PSTATE.<N,Z,C,V> = PredTest(result, result, esize);
P[d] = result;