[PATCH] D74989: [LoopTerminology] Loop Simplify Form

[Stefanos Baziotis via Phabricator via llvm-commits]

baziotis updated this revision to Diff 246416.
baziotis added a comment.

Aligned info in `LoopSimplify.h` with the LoopTerminology.


CHANGES SINCE LAST ACTION
  https://reviews.llvm.org/D74989/new/

https://reviews.llvm.org/D74989

Files:
  llvm/docs/LoopTerminology.rst
  llvm/include/llvm/Transforms/Utils/LoopSimplify.h


Index: llvm/include/llvm/Transforms/Utils/LoopSimplify.h
===================================================================
--- llvm/include/llvm/Transforms/Utils/LoopSimplify.h
+++ llvm/include/llvm/Transforms/Utils/LoopSimplify.h
@@ -8,7 +8,7 @@
 //
 // This pass performs several transformations to transform natural loops into a
 // simpler form, which makes subsequent analyses and transformations simpler and
-// more effective.
+// more effective. It is added by the pass managers when scheduling a LoopPass.
 //
 // Loop pre-header insertion guarantees that there is a single, non-critical
 // entry edge from outside of the loop to the loop header.  This simplifies a
@@ -20,7 +20,8 @@
 // by the loop header).  This simplifies transformations such as store-sinking
 // that are built into LICM.
 //
-// This pass also guarantees that loops will have exactly one backedge.
+// This pass also guarantees that loops will have exactly one backedge
+// (which implies that there is a single latch).
 //
 // Indirectbr instructions introduce several complications. If the loop
 // contains or is entered by an indirectbr instruction, it may not be possible
Index: llvm/docs/LoopTerminology.rst
===================================================================
--- llvm/docs/LoopTerminology.rst
+++ llvm/docs/LoopTerminology.rst
@@ -144,7 +144,19 @@
 Loop Simplify Form
 ==================
 
-TBD
+The Loop Simplify Form is a canonical form that makes
+several analyses and transformations simpler and more effective.
+This loop is ensured by the LoopSimplify (`-loop-simplify`) pass
+and is automatically added by the pass managers when scheduling
+a LoopPass. This pass is implemented in
+`LoopInfo.h http://llvm.org/doxygen/LoopSimplify_8h_source.html`_.
+When it is successful, the loop has:
+
+* A preheader.
+* A single backedge (which implies that there is a single latch).
+* Dedicated exits. That is, no exit block for the loop
+  has a predecessor that is outside the loop. This implies
+  that all exit blocks are dominated by the loop header.
 
 
 Loop Closed SSA (LCSSA)


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