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

Detects dead and undefined subregister lanes across COPY‐like instructions.

== Synopsis

Declared in `<llvm/CodeGen/DetectDeadLanes.h>`

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

== Types

[cols="1,4"]
|===
| Name| Description
| xref:llvm/DeadLaneDetector/VRegInfo.adoc[`VRegInfo`] 
| Contains a bitmask of which lanes of a given virtual register are defined and which ones are actually used.
|===


== Member Functions

[cols="1,4"]
|===
| Name| Description
| xref:llvm/DeadLaneDetector/2constructor.adoc[`DeadLaneDetector`]         [.small]#[constructor]#
| Construct a detector for the given machine register info.
| xref:llvm/DeadLaneDetector/computeSubRegisterLaneBitInfo.adoc[`computeSubRegisterLaneBitInfo`] 
| Update the `DefinedLanes` and the `UsedLanes` for all virtual registers.
| xref:llvm/DeadLaneDetector/getVRegInfo.adoc[`getVRegInfo`] 
| Return the used/defined lane info for virtual register index `RegIdx.`
| xref:llvm/DeadLaneDetector/isDefinedByCopy.adoc[`isDefinedByCopy`] 
| Return true if virtual register index `RegIdx` is defined by a COPY‐like instruction.
| xref:llvm/DeadLaneDetector/transferDefinedLanes.adoc[`transferDefinedLanes`] 
| Given a mask `DefinedLanes` of lanes defined at operand `OpNum` of COPY‐like instruction, determine which lanes are defined at the output operand `Def.`
| xref:llvm/DeadLaneDetector/transferUsedLanes.adoc[`transferUsedLanes`] 
| Given a mask `UsedLanes` used from the output of instruction `MI` determine which lanes are used from operand `MO` of this instruction.
|===



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