Repress sanitization on User dtor. Modify msan macros for applying attribute

to repress sanitization. Move attribute for repressing sanitization to
operator delete for User, MDNode.

Summary: In response to bug 24578, reported against failing LLVM test.

Reviewers: chandlerc, rsmith, eugenis

Subscribers: llvm-commits

Differential Revision: http://reviews.llvm.org/D12335

llvm-svn: 246449

include/llvm/IR/User.h

@@ -72,8 +72,7 @@ protected:
   void growHungoffUses(unsigned N, bool IsPhi = false);
 
 public:
-  ~User() override {
-  }
+  ~User() override {}
   /// \brief Free memory allocated for User and Use objects.
   void operator delete(void *Usr);
   /// \brief Placement delete - required by std, but never called.

include/llvm/Support/Compiler.h

@@ -323,10 +323,12 @@
 #if __has_feature(memory_sanitizer)
 # define LLVM_MEMORY_SANITIZER_BUILD 1
 # include <sanitizer/msan_interface.h>
+# define LLVM_NO_SANITIZE_MEMORY_ATTRIBUTE __attribute__((no_sanitize_memory))
 #else
 # define LLVM_MEMORY_SANITIZER_BUILD 0
 # define __msan_allocated_memory(p, size)
 # define __msan_unpoison(p, size)
+# define LLVM_NO_SANITIZE_MEMORY_ATTRIBUTE
 #endif
 
 /// \macro LLVM_ADDRESS_SANITIZER_BUILD

lib/IR/Metadata.cpp

@@ -401,7 +401,9 @@ void *MDNode::operator new(size_t Size, unsigned NumOps) {
   return Ptr;
 }
 
-void MDNode::operator delete(void *Mem) {
+// Repress memory sanitization, due to use-after-destroy by operator
+// delete. Bug report 24578 identifies this issue.
+LLVM_NO_SANITIZE_MEMORY_ATTRIBUTE void MDNode::operator delete(void *Mem) {
   MDNode *N = static_cast<MDNode *>(Mem);
   size_t OpSize = N->NumOperands * sizeof(MDOperand);
   OpSize = RoundUpToAlignment(OpSize, llvm::alignOf<uint64_t>());

lib/IR/User.cpp

@@ -118,7 +118,9 @@ void *User::operator new(size_t Size) {
 //                         User operator delete Implementation
 //===----------------------------------------------------------------------===//
 
-void User::operator delete(void *Usr) {
+// Repress memory sanitization, due to use-after-destroy by operator
+// delete. Bug report 24578 identifies this issue.
+LLVM_NO_SANITIZE_MEMORY_ATTRIBUTE void User::operator delete(void *Usr) {
   // Hung off uses use a single Use* before the User, while other subclasses
   // use a Use[] allocated prior to the user.
   User *Obj = static_cast<User *>(Usr);