[PATCH] D133687: [LoopVectorize][Fix] Crash when invariant store address is calculated inside loop

[Igor Kirillov via Phabricator via llvm-commits]

igor.kirillov created this revision.
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Generally LICM pass is responsible for sinking out code that calculates
invariant address inside loop as it only needed to be calculated once.
But in rare case it does not happen we will not be vectorizing the
loop.


Repository:
  rG LLVM Github Monorepo

https://reviews.llvm.org/D133687

Files:
  llvm/lib/Transforms/Vectorize/LoopVectorizationLegality.cpp
  llvm/test/Transforms/LoopVectorize/reduction-with-invariant-store.ll


Index: llvm/test/Transforms/LoopVectorize/reduction-with-invariant-store.ll
===================================================================
--- llvm/test/Transforms/LoopVectorize/reduction-with-invariant-store.ll
+++ llvm/test/Transforms/LoopVectorize/reduction-with-invariant-store.ll
@@ -513,3 +513,25 @@
 exit:
   ret void
 }
+
+define void @reduc_store_invariant_calucalated_inside_loop(i32* %dst, i32* readonly %src) {
+; CHECK-LABEL: @reduc_store_invariant_calucalated_inside_loop
+; CHECK-NOT: vector.body:
+entry:
+  br label %for.body
+
+for.body:
+  %sum = phi i32 [ 0, %entry ], [ %add, %for.body ]
+  %iv = phi i64 [ 0, %entry ], [ %iv.next, %for.body ]
+  %gep.src = getelementptr inbounds i32, i32* %src, i64 %iv
+  %0 = load i32, i32* %gep.src, align 4
+  %add = add nsw i32 %sum, %0
+  %gep.dst = getelementptr inbounds i32, i32* %dst, i64 42
+  store i32 %add, i32* %gep.dst, align 4
+  %iv.next = add nuw nsw i64 %iv, 1
+  %exitcond = icmp eq i64 %iv.next, 1000
+  br i1 %exitcond, label %exit, label %for.body
+
+exit:
+  ret void
+}
\ No newline at end of file
Index: llvm/lib/Transforms/Vectorize/LoopVectorizationLegality.cpp
===================================================================
--- llvm/lib/Transforms/Vectorize/LoopVectorizationLegality.cpp
+++ llvm/lib/Transforms/Vectorize/LoopVectorizationLegality.cpp
@@ -932,8 +932,10 @@
   // guaranteed to be stored at the end of the loop. Also, if decision to
   // vectorize loop is made, runtime checks are added so as to make sure that
   // invariant address won't alias with any other objects.
-  if (!LAI->getStoresToInvariantAddresses().empty()) {
-    // For each invariant address, check its last stored value is unconditional.
+  if (!LAI->getStoresToInvariantAddresses().empty() &&
+      !getReductionVars().empty()) {
+    // For each invariant address, check its last stored value is unconditional
+    // and the address is not calculated inside the loop.
     for (StoreInst *SI : LAI->getStoresToInvariantAddresses()) {
       if (isInvariantStoreOfReduction(SI) &&
           blockNeedsPredication(SI->getParent())) {
@@ -944,6 +946,19 @@
             "CantVectorizeStoreToLoopInvariantAddress", ORE, TheLoop);
         return false;
       }
+
+      // Invariant address should be defined outside of loop. LICM pass usually
+      // makes sure it happens, but in rare cases it does not, we do not want
+      // to overcomplicate vectorization to support this case.
+      auto *Ptr = dyn_cast<Instruction>(SI->getPointerOperand());
+      if (Ptr && TheLoop->contains(Ptr)) {
+        reportVectorizationFailure(
+            "Invariant address is calculated inside the loop",
+            "write to a loop invariant address could not "
+            "be vectorized",
+            "CantVectorizeStoreToLoopInvariantAddress", ORE, TheLoop);
+        return false;
+      }
     }
 
     if (LAI->hasDependenceInvolvingLoopInvariantAddress()) {


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