[PATCH] D96706: [llvm] Bug fix: Loop interchange for multiple loops with conditional statements

[Masakazu Ueno via Phabricator via llvm-commits]

masakazu.ueno updated this revision to Diff 323874.

CHANGES SINCE LAST ACTION
  https://reviews.llvm.org/D96706/new/

https://reviews.llvm.org/D96706

Files:
  llvm/lib/Transforms/Scalar/LoopInterchange.cpp
  llvm/test/Transforms/LoopInterchange/lcssa.ll


Index: llvm/test/Transforms/LoopInterchange/lcssa.ll
===================================================================
--- llvm/test/Transforms/LoopInterchange/lcssa.ll
+++ llvm/test/Transforms/LoopInterchange/lcssa.ll
@@ -176,7 +176,7 @@
 }
 
 ; PHI node in inner latch with multiple predecessors.
-; REMARK: Interchanged
+; REMARK: UnsupportedConditionalStatements
 ; REMARK-NEXT: lcssa_05
 
 define void @lcssa_05(i32* %ptr) {
Index: llvm/lib/Transforms/Scalar/LoopInterchange.cpp
===================================================================
--- llvm/lib/Transforms/Scalar/LoopInterchange.cpp
+++ llvm/lib/Transforms/Scalar/LoopInterchange.cpp
@@ -328,8 +328,8 @@
 class LoopInterchangeLegality {
 public:
   LoopInterchangeLegality(Loop *Outer, Loop *Inner, ScalarEvolution *SE,
-                          OptimizationRemarkEmitter *ORE)
-      : OuterLoop(Outer), InnerLoop(Inner), SE(SE), ORE(ORE) {}
+                          DominatorTree *DT, OptimizationRemarkEmitter *ORE)
+      : OuterLoop(Outer), InnerLoop(Inner), SE(SE), DT(DT), ORE(ORE) {}
 
   /// Check if the loops can be interchanged.
   bool canInterchangeLoops(unsigned InnerLoopId, unsigned OuterLoopId,
@@ -347,6 +347,7 @@
 
 private:
   bool tightlyNested(Loop *Outer, Loop *Inner);
+  bool hasConditionalStatements(Loop *L);
   bool containsUnsafeInstructions(BasicBlock *BB);
 
   /// Discover induction and reduction PHIs in the header of \p L. Induction
@@ -361,6 +362,7 @@
   Loop *InnerLoop;
 
   ScalarEvolution *SE;
+  DominatorTree *DT;
 
   /// Interface to emit optimization remarks.
   OptimizationRemarkEmitter *ORE;
@@ -542,7 +544,7 @@
     Loop *InnerLoop = LoopList[InnerLoopId];
     Loop *OuterLoop = LoopList[OuterLoopId];
 
-    LoopInterchangeLegality LIL(OuterLoop, InnerLoop, SE, ORE);
+    LoopInterchangeLegality LIL(OuterLoop, InnerLoop, SE, DT, ORE);
     if (!LIL.canInterchangeLoops(InnerLoopId, OuterLoopId, DependencyMatrix)) {
       LLVM_DEBUG(dbgs() << "Not interchanging loops. Cannot prove legality.\n");
       return false;
@@ -679,6 +681,21 @@
   return nullptr;
 }
 
+/// Return true if the Loop has conditional statements.
+bool LoopInterchangeLegality::hasConditionalStatements(Loop *L) {
+  SmallVector<BasicBlock *, 4> ExitingBlocks;
+  L->getExitingBlocks(ExitingBlocks);
+
+  for (auto BB : L->blocks()) {
+    for (BasicBlock *ExitingBlock : ExitingBlocks) {
+      if (!DT->dominates(BB, ExitingBlock)) {
+        return true;
+      }
+    }
+  }
+  return false;
+}
+
 bool LoopInterchangeLegality::findInductionAndReductions(
     Loop *L, SmallVector<PHINode *, 8> &Inductions, Loop *InnerLoop) {
   if (!L->getLoopLatch() || !L->getLoopPredecessor())
@@ -760,6 +777,19 @@
     return true;
   }
 
+  if (hasConditionalStatements(InnerLoop)) {
+    LLVM_DEBUG(dbgs() << "Loops including conditional statements cannot be"
+                      << " interchanged.\n ");
+    ORE->emit([&]() {
+      return OptimizationRemarkMissed(
+                 DEBUG_TYPE, "UnsupportedConditionalStatements",
+                 InnerLoop->getStartLoc(), InnerLoop->getHeader())
+             << "Loops including conditional statements cannot be "
+                "interchanged.";
+    });
+    return true;
+  }
+
   // TODO: Currently we handle only loops with 1 induction variable.
   if (Inductions.size() != 1) {
     LLVM_DEBUG(dbgs() << "Loops with more than 1 induction variables are not "


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