[#llvm-getShuffleDemandedElts]
= xref:llvm.adoc[llvm]::getShuffleDemandedElts
:relfileprefix: ../
:mrdocs:

Map a shuffle's demanded outputs to demanded elements of its operands.

== Synopsis

Declared in `<llvm/Analysis/VectorUtils.h>`

[source,cpp,subs="verbatim,replacements,macros,-callouts"]
----
bool
getShuffleDemandedElts(
    int SrcWidth,
    xref:llvm/ArrayRef-08.adoc[ArrayRef<int>] Mask,
    xref:llvm/APInt.adoc[APInt] const& DemandedElts,
    xref:llvm/APInt.adoc[APInt]& DemandedLHS,
    xref:llvm/APInt.adoc[APInt]& DemandedRHS,
    bool AllowUndefElts = false);
----

== Description

Transform a shuffle mask's output demanded element mask into demanded element masks for the 2 operands, returns false if the mask isn't valid. Both `DemandedLHS` and `DemandedRHS` are initialised to [SrcWidth]. `AllowUndefElts` permits "‐1" indices to be treated as undef.

== Return Value

True if the mask is valid and the demanded operands were computed.

== Parameters

[cols="1,4"]
|===
| Name| Description
| *SrcWidth*
| Number of elements in each shuffle operand.
| *Mask*
| Shuffle mask being analyzed.
| *DemandedElts*
| Demanded elements of the shuffle result.
| *DemandedLHS*
| Output demanded elements of the left operand.
| *DemandedRHS*
| Output demanded elements of the right operand.
| *AllowUndefElts*
| Whether ‐1 mask indices may be treated as undef.
|===


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