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

Utilities for the induction variable bounds of a loop.

== Synopsis

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

[source,cpp,subs="verbatim,replacements,macros,-callouts"]
----
struct LoopBounds;
----

== Description

Below are some utilities to get the loop guard, loop bounds and induction variable, and to check if a given phinode is an auxiliary induction variable, if the loop is guarded, and if the loop is canonical.

Here is an example:

[,cpp]
----
for (int i = lb; i < ub; i+=step)
  <loop body>
--- pseudo LLVMIR ---
beforeloop:
  guardcmp = (lb < ub)
  if (guardcmp) goto preheader; else goto afterloop
preheader:
loop:
  i_1 = phi[{lb, preheader}, {i_2, latch}]
  <loop body>
  i_2 = i_1 + step
latch:
  cmp = (i_2 < ub)
  if (cmp) goto loop
exit:
afterloop:
----
* getBounds
* getInitialIVValue &hyphen;&hyphen;&gt; lb
* getStepInst &hyphen;&hyphen;&gt; i&lowbar;2 &equals; i&lowbar;1 &plus; step
* getStepValue &hyphen;&hyphen;&gt; step
* getFinalIVValue &hyphen;&hyphen;&gt; ub
* getCanonicalPredicate &hyphen;&hyphen;&gt; &apos;&lt;&apos;
* getDirection &hyphen;&hyphen;&gt; Increasing

* getInductionVariable &hyphen;&hyphen;&gt; i&lowbar;1
* isAuxiliaryInductionVariable(x) &hyphen;&hyphen;&gt; true if x &equals;&equals; i&lowbar;1
* getLoopGuardBranch() &hyphen;&hyphen;&gt; `if (guardcmp) goto preheader&semi; else goto afterloop`
* isGuarded() &hyphen;&hyphen;&gt; true
* isCanonical &hyphen;&hyphen;&gt; false

== Enums

[cols="1,4"]
|===
| Name| Description
| xref:llvm/Loop/LoopBounds/Direction.adoc[`Direction`] 
| Direction of the induction variable across loop iterations&period;
|===


== Member Functions

[cols="1,4"]
|===
| Name| Description
| xref:llvm/Loop/LoopBounds/getCanonicalPredicate.adoc[`getCanonicalPredicate`] 
| Return the canonical predicate for the latch compare instruction, if able to be calcuated&period; Else BAD&lowbar;ICMP&lowbar;PREDICATE&period;
| xref:llvm/Loop/LoopBounds/getDirection.adoc[`getDirection`] 
| Get the direction of the loop&period;
| xref:llvm/Loop/LoopBounds/getFinalIVValue.adoc[`getFinalIVValue`] 
| Get the final value of the loop induction variable&period;
| xref:llvm/Loop/LoopBounds/getInitialIVValue.adoc[`getInitialIVValue`] 
| Get the initial value of the loop induction variable&period;
| xref:llvm/Loop/LoopBounds/getStepInst.adoc[`getStepInst`] 
| Get the instruction that updates the loop induction variable&period;
| xref:llvm/Loop/LoopBounds/getStepValue.adoc[`getStepValue`] 
| Get the step that the loop induction variable gets updated by in each loop iteration&period; Return nullptr if not found&period;
|===


== Static Member Functions

[cols="1,4"]
|===
| Name| Description
| xref:llvm/Loop/LoopBounds/getBounds.adoc[`getBounds`] 
| Return LoopBounds for `IndVar` when its initial, step, and final values can be found&semi; otherwise return std&colon;&colon;nullopt&period;
|===



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