Fix detection of stack-use-after scope for char arrays.

Summary:
Clang inserts GetElementPtrInst so findAllocaForValue was not
able to find allocas.

PR27453

Reviewers: kcc, eugenis

Differential Revision: https://reviews.llvm.org/D22657

llvm-svn: 276374

2 files changed, 24 insertions, 0 deletions

diff --git a/llvm/lib/Transforms/Instrumentation/AddressSanitizer.cpp b/llvm/lib/Transforms/Instrumentation/AddressSanitizer.cpp
index 43d1b377f85..27b68b0387d 100644
--- a/llvm/lib/Transforms/Instrumentation/AddressSanitizer.cpp
+++ b/llvm/lib/Transforms/Instrumentation/AddressSanitizer.cpp
@@ -2286,6 +2286,10 @@ AllocaInst *FunctionStackPoisoner::findAllocaForValue(Value *V) {
         return nullptr;
       Res = IncValueAI;
     }
+  } else if (GetElementPtrInst *EP = dyn_cast<GetElementPtrInst>(V)) {
+    Res = findAllocaForValue(EP->getPointerOperand());
+  } else {
+    DEBUG(dbgs() << "Alloca search canceled on unknown instruction: " << *V << "\n");
   }
   if (Res) AllocaForValue[V] = Res;
   return Res;
diff --git a/llvm/test/Instrumentation/AddressSanitizer/lifetime.ll b/llvm/test/Instrumentation/AddressSanitizer/lifetime.ll
index fb43e882705..f8c8d47e3a3 100644
--- a/llvm/test/Instrumentation/AddressSanitizer/lifetime.ll
+++ b/llvm/test/Instrumentation/AddressSanitizer/lifetime.ll
@@ -91,6 +91,26 @@ bb1:
   ret void
 }
 
+; Check that arguments of lifetime may come from getelementptr nodes.
+define void @getelementptr_args() sanitize_address{
+  ; CHECK-LABEL: define void @getelementptr_args
+entry:
+  %x = alloca [1024 x i8], align 16
+  %d = alloca i8*, align 8
+
+  %0 = getelementptr inbounds [1024 x i8], [1024 x i8]* %x, i64 0, i64 0
+  call void @llvm.lifetime.start(i64 1024, i8* %0)
+  ; CHECK: __asan_unpoison_stack_memory
+
+  store i8* %0, i8** %d, align 8
+
+  call void @llvm.lifetime.end(i64 1024, i8* %0)
+  ; CHECK: __asan_poison_stack_memory
+
+  ret void
+  ; CHECK: __asan_unpoison_stack_memory
+}
+
 define void @zero_sized(i64 %a) #0 {
 ; CHECK-LABEL: define void @zero_sized(i64 %a)