[PATCH] D57033: [LCSSA] Handle case with single new PHI faster.

[Florian Hahn via Phabricator via llvm-commits]

fhahn updated this revision to Diff 183377.
fhahn retitled this revision from "[SSAUpdater] Handle case with single available value faster." to "[LCSSA] Handle case with single new PHI faster.".
fhahn edited the summary of this revision.
fhahn added a comment.

Moved change to LCSSA. Also shortens the runtime a tiny bit more.


CHANGES SINCE LAST ACTION
  https://reviews.llvm.org/D57033/new/

https://reviews.llvm.org/D57033

Files:
  llvm/lib/Transforms/Utils/LCSSA.cpp


Index: llvm/lib/Transforms/Utils/LCSSA.cpp
===================================================================
--- llvm/lib/Transforms/Utils/LCSSA.cpp
+++ llvm/lib/Transforms/Utils/LCSSA.cpp
@@ -197,6 +197,16 @@
         continue;
       }
 
+      // If we added a single PHI, it must dominate all uses and we can directly
+      // rename it.
+      if (AddedPHIs.size() == 1) {
+        // Tell the VHs that the uses changed. This updates SCEV's caches.
+        if (UseToRewrite->get()->hasValueHandle())
+          ValueHandleBase::ValueIsRAUWd(*UseToRewrite, AddedPHIs[0]);
+        UseToRewrite->set(AddedPHIs[0]);
+        continue;
+      }
+
       // Otherwise, do full PHI insertion.
       SSAUpdate.RewriteUse(*UseToRewrite);
     }
@@ -212,8 +222,9 @@
         continue;
       // We currently only handle debug values residing in blocks where we have
       // inserted a PHI instruction.
-      if (Value *V = SSAUpdate.FindValueForBlock(UserBB))
-        DVI->setOperand(0, MetadataAsValue::get(Ctx, ValueAsMetadata::get(V)));
+      Value *V = AddedPHIs.size() == 1 ? AddedPHIs[0]
+                                       : SSAUpdate.FindValueForBlock(UserBB);
+      DVI->setOperand(0, MetadataAsValue::get(Ctx, ValueAsMetadata::get(V)));
     }
 
     // SSAUpdater might have inserted phi-nodes inside other loops. We'll need


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