[PATCH] D54517: [CGP] Limit Complex Addressing mode by number of BasicBlocks to traverse

[Serguei Katkov via Phabricator via llvm-commits]

skatkov created this revision.
skatkov added reviewers: john.brawn, reames, bjope.

The finding the combined complex addressing mode in some cases becomes
expensive. This CL limits the work by number of basic blocks to traverse.

This is a fix for PR39625.


https://reviews.llvm.org/D54517

Files:
  lib/CodeGen/CodeGenPrepare.cpp


Index: lib/CodeGen/CodeGenPrepare.cpp
===================================================================
--- lib/CodeGen/CodeGenPrepare.cpp
+++ lib/CodeGen/CodeGenPrepare.cpp
@@ -192,6 +192,11 @@
     cl::desc("Disables combining addressing modes with different parts "
              "in optimizeMemoryInst."));
 
+static cl::opt<int> ComplexAddrModesThreshold(
+    "complex-addr-modes-threshold", cl::Hidden, cl::init(100),
+    cl::desc("Stop processing complex addressing mode optimization"
+             " if number of basic blocks to process exceeds threshold"));
+
 static cl::opt<bool>
 AddrSinkNewPhis("addr-sink-new-phis", cl::Hidden, cl::init(false),
                 cl::desc("Allow creation of Phis in Address sinking."));
@@ -3084,7 +3089,13 @@
     // First step, DFS to create PHI nodes for all intermediate blocks.
     // Also fill traverse order for the second step.
     SmallVector<ValueInBB, 32> TraverseOrder;
-    InsertPlaceholders(Map, TraverseOrder, ST);
+    if (!InsertPlaceholders(Map, TraverseOrder, ST)) {
+      LLVM_DEBUG(
+          dbgs() << "Stop complex addressing mode due to exceed of threshold: "
+                 << TraverseOrder.size());
+      ST.destroyNewNodes(CommonType);
+      return nullptr;
+    }
 
     // Second Step, fill new nodes by merged values and simplify if possible.
     FillPlaceholders(Map, TraverseOrder, ST);
@@ -3258,7 +3269,8 @@
   /// a placeholder Phi or Select.
   /// Reports all new created Phi/Select nodes by adding them to set.
   /// Also reports and order in what basic blocks have been traversed.
-  void InsertPlaceholders(FoldAddrToValueMapping &Map,
+  /// Return false if size of TraverseOrder exceeds threshold.
+  bool InsertPlaceholders(FoldAddrToValueMapping &Map,
                           SmallVectorImpl<ValueInBB> &TraverseOrder,
                           SimplificationTracker &ST) {
     SmallVector<ValueInBB, 32> Worklist;
@@ -3278,6 +3290,8 @@
       if (Map.find(Current) != Map.end())
         continue;
       TraverseOrder.push_back(Current);
+      if ((int)TraverseOrder.size() > ComplexAddrModesThreshold)
+        return false;
 
       Value *CurrentValue = Current.first;
       BasicBlock *CurrentBlock = Current.second;
@@ -3327,6 +3341,7 @@
           Worklist.push_back({ CurrentPhi->getIncomingValueForBlock(B), B });
       }
     }
+    return true;
   }
 
   bool addrModeCombiningAllowed() {


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