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

Constrain a loop to run within a given iteration range.

== Synopsis

Declared in `<llvm/Transforms/Utils/LoopConstrainer.h>`

[source,cpp,subs="verbatim,replacements,macros,-callouts"]
----
class LoopConstrainer;
----

== Description

The algorithm this class implements is given a Loop and a range [Begin,] End). The algorithm then tries to break out a "main loop" out of the loop it is given in a way that the "main loop" runs with the induction variable in a subset of [Begin, End). The algorithm emits appropriate pre and post] loops to run any remaining iterations. The pre loop runs any iterations in which the induction variable is < Begin, and the post loop runs any iterations in which the induction variable is >= End.

== Types

[cols="1,4"]
|===
| Name| Description
| xref:llvm/LoopConstrainer/SubRanges.adoc[`SubRanges`] 
| Subranges that restrict the main loop's iteration space.
|===


== Member Functions

[cols="1,4"]
|===
| Name| Description
| xref:llvm/LoopConstrainer/2constructor.adoc[`LoopConstrainer`]         [.small]#[constructor]#
| Construct a constrainer for loop `L` with structure `LS` and range `SR.`
| xref:llvm/LoopConstrainer/run.adoc[`run`] 
| Run the loop constraining algorithm.
|===



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