[asan] Fix invalid debug info for promotable allocas

Since r230724 ("Skip promotable allocas to improve performance at -O0"), there is a regression in the generated debug info for those non-instrumented variables. When inspecting such a variable's value in LLDB, you often get garbage instead of the actual value. ASan instrumentation is inserted before the creation of the non-instrumented alloca. The only allocas that are considered standard stack variables are the ones declared in the first basic-block, but the initial instrumentation setup in the function breaks that invariant.

This patch makes sure uninstrumented allocas stay in the first BB.

Differential Revision: http://reviews.llvm.org/D11179

llvm-svn: 242510

1 files changed, 7 insertions, 1 deletions

diff --git a/llvm/lib/Transforms/Instrumentation/AddressSanitizer.cpp b/llvm/lib/Transforms/Instrumentation/AddressSanitizer.cpp
index e7ef9f96edc..a67a9a217a4 100644
--- a/llvm/lib/Transforms/Instrumentation/AddressSanitizer.cpp
+++ b/llvm/lib/Transforms/Instrumentation/AddressSanitizer.cpp
@@ -525,6 +525,7 @@ struct FunctionStackPoisoner : public InstVisitor<FunctionStackPoisoner> {
   ShadowMapping Mapping;
 
   SmallVector<AllocaInst *, 16> AllocaVec;
+  SmallVector<AllocaInst *, 16> NonInstrumentedStaticAllocaVec;
   SmallVector<Instruction *, 8> RetVec;
   unsigned StackAlignment;
 
@@ -625,7 +626,10 @@ struct FunctionStackPoisoner : public InstVisitor<FunctionStackPoisoner> {
 
   /// \brief Collect Alloca instructions we want (and can) handle.
   void visitAllocaInst(AllocaInst &AI) {
-    if (!ASan.isInterestingAlloca(AI)) return;
+    if (!ASan.isInterestingAlloca(AI)) {
+      if (AI.isStaticAlloca()) NonInstrumentedStaticAllocaVec.push_back(&AI);
+      return;
+    }
 
     StackAlignment = std::max(StackAlignment, AI.getAlignment());
     if (ASan.isDynamicAlloca(AI))
@@ -1734,6 +1738,8 @@ void FunctionStackPoisoner::poisonStack() {
   IRBuilder<> IRB(InsBefore);
   IRB.SetCurrentDebugLocation(EntryDebugLocation);
 
+  for (auto *AI : NonInstrumentedStaticAllocaVec) AI->moveBefore(InsBefore);
+
   SmallVector<ASanStackVariableDescription, 16> SVD;
   SVD.reserve(AllocaVec.size());
   for (AllocaInst *AI : AllocaVec) {