[llvm-commits] [llvm] r100044 - /llvm/trunk/lib/Transforms/Scalar/CodeGenPrepare.cpp

[Dale Johannesen]

Author: johannes
Date: Wed Mar 31 15:37:15 2010
New Revision: 100044

URL: http://llvm.org/viewvc/llvm-project?rev=100044&view=rev
Log:
Fix a nasty dangling-pointer heisenbug that could
generate wrong code pretty much anywhere AFAICT.
A case that hits the bug reproducibly is impossible,
but the situation was like this:
Addr = ...
Store -> Addr
Addr2 = GEP , 0, 0
Store -> Addr2
Handling the first store, the code changed replaced Addr
with a sunkaddr and deleted Addr, but not its table
entry.  Code in OptimizedBlock replaced Addr2 with a
bitcast; if that happened to reuse the memory of Addr,
the old table entry was erroneously found when handling
the second store.


Modified:
    llvm/trunk/lib/Transforms/Scalar/CodeGenPrepare.cpp

Modified: llvm/trunk/lib/Transforms/Scalar/CodeGenPrepare.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Transforms/Scalar/CodeGenPrepare.cpp?rev=100044&r1=100043&r2=100044&view=diff
==============================================================================
--- llvm/trunk/lib/Transforms/Scalar/CodeGenPrepare.cpp (original)
+++ llvm/trunk/lib/Transforms/Scalar/CodeGenPrepare.cpp Wed Mar 31 15:37:15 2010
@@ -714,8 +714,12 @@
 
   MemoryInst->replaceUsesOfWith(Addr, SunkAddr);
 
-  if (Addr->use_empty())
+  if (Addr->use_empty()) {
     RecursivelyDeleteTriviallyDeadInstructions(Addr);
+    // This address is now available for reassignment, so erase the table entry;
+    // we don't want to match some completely different instruction.
+    SunkAddrs[Addr] = 0;
+  }
   return true;
 }