[asan] Add a comment explaining why non-instrumented allocas are moved.

Addition to r242510. git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@242561 91177308-0d34-0410-b5e6-96231b3b80d8
CIB · Jul 17, 2015 · b8850e4 · b8850e4
1 parent beda80e
commit b8850e4
Showing 1 changed file with 3 additions and 0 deletions.
diff --git a/lib/Transforms/Instrumentation/AddressSanitizer.cpp b/lib/Transforms/Instrumentation/AddressSanitizer.cpp
@@ -1738,6 +1738,9 @@ void FunctionStackPoisoner::poisonStack() {
   IRBuilder<> IRB(InsBefore);
   IRB.SetCurrentDebugLocation(EntryDebugLocation);
 
+  // Make sure non-instrumented allocas stay in the first basic block.
+  // Otherwise, debug info is broken, because only first-basic-block allocas are
+  // treated as regular stack slots.
   for (auto *AI : NonInstrumentedStaticAllocaVec) AI->moveBefore(InsBefore);
 
   SmallVector<ASanStackVariableDescription, 16> SVD;