[PATCH] D134083: [IVDescriptors] Before moving an instruction in SinkAfter checking if it is target of other instructions

[Guozhi Wei via Phabricator via llvm-commits]

Carrot updated this revision to Diff 463040.
Carrot marked 2 inline comments as done.

CHANGES SINCE LAST ACTION
  https://reviews.llvm.org/D134083/new/

https://reviews.llvm.org/D134083

Files:
  llvm/lib/Analysis/IVDescriptors.cpp
  llvm/test/Transforms/LoopVectorize/first-order-recurrence-chains.ll


Index: llvm/test/Transforms/LoopVectorize/first-order-recurrence-chains.ll
===================================================================
--- llvm/test/Transforms/LoopVectorize/first-order-recurrence-chains.ll
+++ llvm/test/Transforms/LoopVectorize/first-order-recurrence-chains.ll
@@ -637,3 +637,30 @@
 exit:
   ret void
 }
+
+; Make sure LLVM doesn't generate wrong data in SinkAfter, and causes crash in
+; loop vectorizer.
+define void @test_crash(ptr %p) {
+; CHECK-LABEL: @test_crash
+; CHECK:       ret
+Entry:
+  br label %Loop
+
+Loop:
+  %for.1 = phi double [ %iv1, %Loop ], [ 0.000000e+00, %Entry ]
+  %for.2 = phi double [ %iv2, %Loop ], [ 0.000000e+00, %Entry ]
+  %for.3 = phi double [ %for.2, %Loop ], [ 0.000000e+00, %Entry ]
+  %for.4 = phi i64 [ %count, %Loop ], [ 0, %Entry ]
+  %USE_2_INDVARS = fdiv double %for.3, %for.1
+  %div = fdiv double 0.000000e+00, %for.1
+  %iv1 = load double, ptr null, align 8
+  %count = add nuw nsw i64 %for.4, 1
+  %iv2 = load double, ptr null, align 8
+  store double %div, ptr %p, align 8
+  %cond = icmp eq i64 %count, 0
+  br i1 %cond, label %End, label %Loop
+
+End:
+  ret void
+}
+
Index: llvm/lib/Analysis/IVDescriptors.cpp
===================================================================
--- llvm/lib/Analysis/IVDescriptors.cpp
+++ llvm/lib/Analysis/IVDescriptors.cpp
@@ -1025,6 +1025,16 @@
       // Previous. Nothing left to do.
       if (DT->dominates(Previous, OtherPrev) || Previous == OtherPrev)
         return true;
+
+      // If there are other instructions to be sunk after SinkCandidate, remove
+      // and re-insert SinkCandidate can break those instructions. Bail out for
+      // simplicity.
+      if (any_of(SinkAfter,
+          [SinkCandidate](const std::pair<Instruction *, Instruction *> &P) {
+            return P.second == SinkCandidate;
+          }))
+        return false;
+
       // Otherwise, Previous comes after OtherPrev and SinkCandidate needs to be
       // re-sunk to Previous, instead of sinking to OtherPrev. Remove
       // SinkCandidate from SinkAfter to ensure it's insert position is updated.


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