[llvm] a10409f - [MemorySSAUpdater] Simplify updates when only deleting edges.

[Alina Sbirlea via llvm-commits]

Author: Alina Sbirlea
Date: 2021-09-01T15:48:20-07:00
New Revision: a10409fe23c35a7eed0f39d12624af229d3877e1

URL: https://github.com/llvm/llvm-project/commit/a10409fe23c35a7eed0f39d12624af229d3877e1
DIFF: https://github.com/llvm/llvm-project/commit/a10409fe23c35a7eed0f39d12624af229d3877e1.diff

LOG: [MemorySSAUpdater] Simplify updates when only deleting edges.

When performing only edge deletion, we don't need to do the DT updates
back and forth. Check for the existance of insert updates to simplify
this.

Added: 
    

Modified: 
    llvm/lib/Analysis/MemorySSAUpdater.cpp

Removed: 
    


################################################################################
diff  --git a/llvm/lib/Analysis/MemorySSAUpdater.cpp b/llvm/lib/Analysis/MemorySSAUpdater.cpp
index 616864f360bf..0eb338383c56 100644
--- a/llvm/lib/Analysis/MemorySSAUpdater.cpp
+++ b/llvm/lib/Analysis/MemorySSAUpdater.cpp
@@ -822,25 +822,30 @@ void MemorySSAUpdater::applyUpdates(ArrayRef<CFGUpdate> Updates,
   }
 
   if (!DeleteUpdates.empty()) {
-    if (!UpdateDT) {
-      SmallVector<CFGUpdate, 0> Empty;
-      // Deletes are reversed applied, because this CFGView is pretending the
-      // deletes did not happen yet, hence the edges still exist.
-      DT.applyUpdates(Empty, RevDeleteUpdates);
+    if (!InsertUpdates.empty()) {
+      if (!UpdateDT) {
+        SmallVector<CFGUpdate, 0> Empty;
+        // Deletes are reversed applied, because this CFGView is pretending the
+        // deletes did not happen yet, hence the edges still exist.
+        DT.applyUpdates(Empty, RevDeleteUpdates);
+      } else {
+        // Apply all updates, with the RevDeleteUpdates as PostCFGView.
+        DT.applyUpdates(Updates, RevDeleteUpdates);
+      }
+
+      // Note: the MSSA update below doesn't distinguish between a GD with
+      // (RevDelete,false) and (Delete, true), but this matters for the DT
+      // updates above; for "children" purposes they are equivalent; but the
+      // updates themselves convey the desired update, used inside DT only.
+      GraphDiff<BasicBlock *> GD(RevDeleteUpdates);
+      applyInsertUpdates(InsertUpdates, DT, &GD);
+      // Update DT to redelete edges; this matches the real CFG so we can
+      // perform the standard update without a postview of the CFG.
+      DT.applyUpdates(DeleteUpdates);
     } else {
-      // Apply all updates, with the RevDeleteUpdates as PostCFGView.
-      DT.applyUpdates(Updates, RevDeleteUpdates);
+      if (UpdateDT)
+        DT.applyUpdates(DeleteUpdates);
     }
-
-    // Note: the MSSA update below doesn't distinguish between a GD with
-    // (RevDelete,false) and (Delete, true), but this matters for the DT
-    // updates above; for "children" purposes they are equivalent; but the
-    // updates themselves convey the desired update, used inside DT only.
-    GraphDiff<BasicBlock *> GD(RevDeleteUpdates);
-    applyInsertUpdates(InsertUpdates, DT, &GD);
-    // Update DT to redelete edges; this matches the real CFG so we can perform
-    // the standard update without a postview of the CFG.
-    DT.applyUpdates(DeleteUpdates);
   } else {
     if (UpdateDT)
       DT.applyUpdates(Updates);