[llvm] r268269 - [CFLAA] Fix a use-of-invalid-pointer bug.

[George Burgess IV via llvm-commits]

Author: gbiv
Date: Mon May  2 13:09:19 2016
New Revision: 268269

URL: http://llvm.org/viewvc/llvm-project?rev=268269&view=rev
Log:
[CFLAA] Fix a use-of-invalid-pointer bug.

As shown in the diff, we used to add to CFLAA's cache by doing
`Cache[Fn] = buildSetsFrom(Fn)`. `buildSetsFrom(Fn)` may cause `Cache`
to reallocate its underlying storage, if this happens and `Cache[Fn]`
was evaluated prior to `buildSetsFrom(Fn)`, then we'll store the result
to a bad address.

Patch by Jia Chen.

Modified:
    llvm/trunk/lib/Analysis/CFLAliasAnalysis.cpp

Modified: llvm/trunk/lib/Analysis/CFLAliasAnalysis.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Analysis/CFLAliasAnalysis.cpp?rev=268269&r1=268268&r2=268269&view=diff
==============================================================================
--- llvm/trunk/lib/Analysis/CFLAliasAnalysis.cpp (original)
+++ llvm/trunk/lib/Analysis/CFLAliasAnalysis.cpp Mon May  2 13:09:19 2016
@@ -994,7 +994,12 @@ void CFLAAResult::scan(Function *Fn) {
   assert(InsertPair.second &&
          "Trying to scan a function that has already been cached");
 
-  Cache[Fn] = buildSetsFrom(Fn);
+  // Note that we can't do Cache[Fn] = buildSetsFrom(Fn) here: the function call
+  // may get evaluated after operator[], potentially triggering a DenseMap
+  // resize and invalidating the reference returned by operator[]
+  auto FunInfo = buildSetsFrom(Fn);
+  Cache[Fn] = std::move(FunInfo);
+
   Handles.push_front(FunctionHandle(Fn, this));
 }