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

diff --git a/lib/Transforms/Scalar/DeadStoreElimination.cpp b/lib/Transforms/Scalar/DeadStoreElimination.cpp
index 320afa19d5fbc30c3728c7253206e7c15f09a6ee..09c01d314124e65ff3c7767db50d7f99eeb93ee9 100644 (file)
--- a/lib/Transforms/Scalar/DeadStoreElimination.cpp
+++ b/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;
     }
     

diff --git a/test/Transforms/DeadStoreElimination/crash.ll b/test/Transforms/DeadStoreElimination/crash.ll
index f89f8f5185c68c0866ada6a0c2b857339df3b61c..6d8ba71b2094d4665eb0852459ea9e250e3d89b3 100644 (file)
--- a/test/Transforms/DeadStoreElimination/crash.ll
+++ b/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
+}
\ No newline at end of file