Retry: [ubsan] Detect UB loads from bitfields

It's possible to load out-of-range values from bitfields backed by a
boolean or an enum. Check for UB loads from bitfields.

This is the motivating example:

  struct S {
    BOOL b : 1; // Signed ObjC BOOL.
  };

  S s;
  s.b = 1; // This is actually stored as -1.
  if (s.b == 1) // Evaluates to false, -1 != 1.
    ...

Changes since the original commit:

- Single-bit bools are a special case (see CGF::EmitFromMemory), and we
  can't avoid dealing with them when loading from a bitfield. Don't try to
  insert a check in this case.

Differential Revision: https://reviews.llvm.org/D30423

llvm-svn: 297389

1 files changed, 1 insertions, 1 deletions

diff --git a/clang/lib/CodeGen/CGAtomic.cpp b/clang/lib/CodeGen/CGAtomic.cpp
index 9287e46127b..28e20b53d65 100644
--- a/clang/lib/CodeGen/CGAtomic.cpp
+++ b/clang/lib/CodeGen/CGAtomic.cpp
@@ -1181,7 +1181,7 @@ RValue AtomicInfo::convertAtomicTempToRValue(Address addr,
   if (LVal.isBitField())
     return CGF.EmitLoadOfBitfieldLValue(
         LValue::MakeBitfield(addr, LVal.getBitFieldInfo(), LVal.getType(),
-                             LVal.getAlignmentSource()));
+                             LVal.getAlignmentSource()), loc);
   if (LVal.isVectorElt())
     return CGF.EmitLoadOfLValue(
         LValue::MakeVectorElt(addr, LVal.getVectorIdx(), LVal.getType(),