[llvm] r373383 - [MemorySSA] Check for unreachable blocks when getting last definition.

[Alina Sbirlea via llvm-commits]

Author: asbirlea
Date: Tue Oct  1 12:09:50 2019
New Revision: 373383

URL: http://llvm.org/viewvc/llvm-project?rev=373383&view=rev
Log:
[MemorySSA] Check for unreachable blocks when getting last definition.

If a single predecessor is found, still check if the block is
unreachable. The test that found this had a self loop unreachable block.
Resolves PR43493.

Added:
    llvm/trunk/test/Analysis/MemorySSA/pr43493.ll
Modified:
    llvm/trunk/lib/Analysis/MemorySSAUpdater.cpp

Modified: llvm/trunk/lib/Analysis/MemorySSAUpdater.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Analysis/MemorySSAUpdater.cpp?rev=373383&r1=373382&r2=373383&view=diff
==============================================================================
--- llvm/trunk/lib/Analysis/MemorySSAUpdater.cpp (original)
+++ llvm/trunk/lib/Analysis/MemorySSAUpdater.cpp Tue Oct  1 12:09:50 2019
@@ -839,6 +839,9 @@ void MemorySSAUpdater::applyInsertUpdate
       } else {
         // Single predecessor, BB cannot be dead. GetLastDef of Pred.
         assert(Count == 1 && Pred && "Single predecessor expected.");
+        // BB can be unreachable though, return LoE if that is the case.
+        if (!DT.getNode(BB))
+          return MSSA->getLiveOnEntryDef();
         BB = Pred;
       }
     };

Added: llvm/trunk/test/Analysis/MemorySSA/pr43493.ll
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/test/Analysis/MemorySSA/pr43493.ll?rev=373383&view=auto
==============================================================================
--- llvm/trunk/test/Analysis/MemorySSA/pr43493.ll (added)
+++ llvm/trunk/test/Analysis/MemorySSA/pr43493.ll Tue Oct  1 12:09:50 2019
@@ -0,0 +1,27 @@
+; RUN: opt -enable-mssa-loop-dependency=true -loop-rotate -verify-memoryssa -S %s | FileCheck %s
+; REQUIRES: asserts
+
+; CHECK-LABEL: @func_35()
+define void @func_35() {
+entry:
+  br i1 undef, label %for.cond1704.preheader, label %return
+
+for.cond1704.preheader:                           ; preds = %entry
+  br label %for.cond1704
+
+for.cond1704:                                     ; preds = %for.cond1704.preheader, %for.body1707
+  br i1 false, label %for.body1707, label %return.loopexit
+
+for.body1707:                                     ; preds = %for.cond1704
+  store i32 1712, i32* undef, align 1
+  br label %for.cond1704
+
+for.body1102:                                     ; preds = %for.body1102
+  br i1 undef, label %for.body1102, label %return
+
+return.loopexit:                                  ; preds = %for.cond1704
+  br label %return
+
+return:                                           ; preds = %return.loopexit, %for.body1102, %entry
+  ret void
+}