[asan] Fix instruction emission ordering with dynamic shadow.

Summary:
Instrumentation to copy byval arguments is now correctly inserted
after the dynamic shadow base is loaded.

Reviewers: vitalybuka, eugenis

Reviewed By: vitalybuka

Subscribers: hiraditya, llvm-commits

Differential Revision: https://reviews.llvm.org/D36533

llvm-svn: 310503

1 files changed, 8 insertions, 3 deletions

diff --git a/llvm/lib/Transforms/Instrumentation/AddressSanitizer.cpp b/llvm/lib/Transforms/Instrumentation/AddressSanitizer.cpp
index f8d255273b2..058b8fa33df 100644
--- a/llvm/lib/Transforms/Instrumentation/AddressSanitizer.cpp
+++ b/llvm/lib/Transforms/Instrumentation/AddressSanitizer.cpp
@@ -756,7 +756,7 @@ struct FunctionStackPoisoner : public InstVisitor<FunctionStackPoisoner> {
   bool runOnFunction() {
     if (!ClStack) return false;
 
-    if (ClRedzoneByvalArgs && Mapping.Offset != kDynamicShadowSentinel)
+    if (ClRedzoneByvalArgs)
       copyArgsPassedByValToAllocas();
 
     // Collect alloca, ret, lifetime instructions etc.
@@ -2546,8 +2546,13 @@ static int StackMallocSizeClass(uint64_t LocalStackSize) {
 }
 
 void FunctionStackPoisoner::copyArgsPassedByValToAllocas() {
-  BasicBlock &FirstBB = *F.begin();
-  IRBuilder<> IRB(&FirstBB, FirstBB.getFirstInsertionPt());
+  Instruction *CopyInsertPoint = &F.front().front();
+  if (CopyInsertPoint == ASan.LocalDynamicShadow) {
+    // Insert after the dynamic shadow location is determined
+    CopyInsertPoint = CopyInsertPoint->getNextNode();
+    assert(CopyInsertPoint);
+  }
+  IRBuilder<> IRB(CopyInsertPoint);
   const DataLayout &DL = F.getParent()->getDataLayout();
   for (Argument &Arg : F.args()) {
     if (Arg.hasByValAttr()) {