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

Compute the demanded elements mask of horizontal binary operations.

== Synopsis

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

[source,cpp,subs="verbatim,replacements,macros,-callouts"]
----
void
getHorizDemandedEltsForFirstOperand(
    unsigned int VectorBitWidth,
    xref:llvm/APInt.adoc[APInt] const& DemandedElts,
    xref:llvm/APInt.adoc[APInt]& DemandedLHS,
    xref:llvm/APInt.adoc[APInt]& DemandedRHS);
----

== Description

A horizontal operation combines two adjacent elements in a vector operand. This function returns a mask for the elements that correspond to the first operand of this horizontal combination. For example, for two vectors [X1, X2, X3, X4]and [Y1, Y2, Y3, Y4], the resulting mask can include the elements X1, X3, Y1, and Y3. To get the other operands, simply shift the result of this function to the left by 1.

== Parameters

[cols="1,4"]
|===
| Name| Description
| *VectorBitWidth*
| the total bit width of the vector
| *DemandedElts*
| the demanded elements mask for the operation
| *DemandedLHS*
| the demanded elements mask for the left operand
| *DemandedRHS*
| the demanded elements mask for the right operand
|===


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