[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.
    ...

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

llvm-svn: 297298

0 files changed, 0 insertions, 0 deletions