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

Create a bitmask with the N left‐most bits set to 1, and all other bits set to 0. Only unsigned types are allowed.

== Synopsis

Declared in `<llvm/Support/MathExtras.h>`

[source,cpp,subs="verbatim,replacements,macros,-callouts"]
----
template<typename T>
constexpr
T
maskLeadingOnes(unsigned int N);
----

== Return Value

A bitmask with the N left‐most bits set.

== Parameters

[cols="1,4"]
|===
| Name| Description
| *N*
| Number of leading one‐bits in the mask.
|===


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