Make DSE only scan blocks that are reachable from the entry

block.  Other blocks may have pointer cycles that will crash
basicaa and other alias analyses.  In any case, there is no
point wasting cycles optimizing dead blocks.  This fixes 
rdar://7635088


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@95852 91177308-0d34-0410-b5e6-96231b3b80d8

lib/Transforms/Scalar/DeadStoreElimination.cpp

@@ -44,8 +44,14 @@ namespace {
 
     virtual bool runOnFunction(Function &F) {
       bool Changed = false;
+      
+      DominatorTree &DT = getAnalysis<DominatorTree>();
+      
       for (Function::iterator I = F.begin(), E = F.end(); I != E; ++I)
-        Changed |= runOnBasicBlock(*I);
+        // Only check non-dead blocks.  Dead blocks may have strange pointer
+        // cycles that will confuse alias analysis.
+        if (DT.isReachableFromEntry(I))
+          Changed |= runOnBasicBlock(*I);
       return Changed;
     }
     

test/Transforms/DeadStoreElimination/crash.ll

@@ -41,3 +41,17 @@ bb14:                                             ; preds = %bb4
 }
 
 declare void @llvm.memcpy.i64(i8* nocapture, i8* nocapture, i64, i32) nounwind
+
+
+; rdar://7635088
+define i32 @test3() {
+entry:
+  ret i32 0
+  
+dead:
+  %P2 = getelementptr i32 *%P2, i32 52
+  %Q2 = getelementptr i32 *%Q2, i32 52
+  store i32 4, i32* %P2
+  store i32 4, i32* %Q2
+  br label %dead
+}