[llvm] r262683 - Annotate our undefined behaviour to sneak it past the sanitizers

[Justin Bogner via llvm-commits]

Author: bogner
Date: Thu Mar  3 19:52:47 2016
New Revision: 262683

URL: http://llvm.org/viewvc/llvm-project?rev=262683&view=rev
Log:
Annotate our undefined behaviour to sneak it past the sanitizers

We have known UB in some ilists where we static cast half nodes to
(larger) derived types and use the address. See llvm.org/PR26753.

This needs to be fixed, but in the meantime it'd be nice if running
ubsan didn't complain. This adds annotations in the two places where
ubsan complains while running check-all of a sanitized clang build.

Modified:
    llvm/trunk/include/llvm/CodeGen/MachineFunction.h
    llvm/trunk/include/llvm/Support/Compiler.h
    llvm/trunk/include/llvm/Transforms/Utils/MemorySSA.h

Modified: llvm/trunk/include/llvm/CodeGen/MachineFunction.h
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/include/llvm/CodeGen/MachineFunction.h?rev=262683&r1=262682&r2=262683&view=diff
==============================================================================
--- llvm/trunk/include/llvm/CodeGen/MachineFunction.h (original)
+++ llvm/trunk/include/llvm/CodeGen/MachineFunction.h Thu Mar  3 19:52:47 2016
@@ -24,6 +24,7 @@
 #include "llvm/IR/Metadata.h"
 #include "llvm/Support/Allocator.h"
 #include "llvm/Support/ArrayRecycler.h"
+#include "llvm/Support/Compiler.h"
 #include "llvm/Support/Recycler.h"
 
 namespace llvm {
@@ -50,6 +51,8 @@ struct ilist_traits<MachineBasicBlock>
     : public ilist_default_traits<MachineBasicBlock> {
   mutable ilist_half_node<MachineBasicBlock> Sentinel;
 public:
+  // FIXME: This downcast is UB. See llvm.org/PR26753.
+  LLVM_NO_SANITIZE("object-size")
   MachineBasicBlock *createSentinel() const {
     return static_cast<MachineBasicBlock*>(&Sentinel);
   }

Modified: llvm/trunk/include/llvm/Support/Compiler.h
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/include/llvm/Support/Compiler.h?rev=262683&r1=262682&r2=262683&view=diff
==============================================================================
--- llvm/trunk/include/llvm/Support/Compiler.h (original)
+++ llvm/trunk/include/llvm/Support/Compiler.h Thu Mar  3 19:52:47 2016
@@ -415,6 +415,14 @@ void AnnotateIgnoreWritesEnd(const char
 # define TsanIgnoreWritesEnd()
 #endif
 
+/// \macro LLVM_NO_SANITIZE
+/// \brief Disable a particular sanitizer for a function.
+#if __has_attribute(no_sanitize)
+#define LLVM_NO_SANITIZE(KIND) __attribute__((no_sanitize(KIND)))
+#else
+#define LLVM_NO_SANITIZE(KIND)
+#endif
+
 /// \brief Mark debug helper function definitions like dump() that should not be
 /// stripped from debug builds.
 // FIXME: Move this to a private config.h as it's not usable in public headers.

Modified: llvm/trunk/include/llvm/Transforms/Utils/MemorySSA.h
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/include/llvm/Transforms/Utils/MemorySSA.h?rev=262683&r1=262682&r2=262683&view=diff
==============================================================================
--- llvm/trunk/include/llvm/Transforms/Utils/MemorySSA.h (original)
+++ llvm/trunk/include/llvm/Transforms/Utils/MemorySSA.h Thu Mar  3 19:52:47 2016
@@ -86,6 +86,7 @@
 #include "llvm/IR/User.h"
 #include "llvm/IR/Value.h"
 #include "llvm/Pass.h"
+#include "llvm/Support/Compiler.h"
 
 namespace llvm {
 class BasicBlock;
@@ -153,7 +154,8 @@ private:
 template <>
 struct ilist_traits<MemoryAccess> : public ilist_default_traits<MemoryAccess> {
   /// See details of the instruction class for why this trick works
-  /// FIXME: The downcast is UB.
+  // FIXME: This downcast is UB. See llvm.org/PR26753.
+  LLVM_NO_SANITIZE("object-size")
   MemoryAccess *createSentinel() const {
     return static_cast<MemoryAccess *>(&Sentinel);
   }