[clang][UBSan] Add implicit conversion check for bitfields (#75481)

This patch implements the implicit truncation and implicit sign change
checks for bitfields using UBSan. E.g.,
`-fsanitize=implicit-bitfield-truncation` and
`-fsanitize=implicit-bitfield-sign-change`.

1 files changed, 15 insertions, 0 deletions

diff --git a/clang/lib/CodeGen/CodeGenFunction.h b/clang/lib/CodeGen/CodeGenFunction.h
index e2a7e28..99a7f51 100644
--- a/clang/lib/CodeGen/CodeGenFunction.h
+++ b/clang/lib/CodeGen/CodeGenFunction.h
@@ -2786,6 +2786,21 @@ public:
   /// expression and compare the result against zero, returning an Int1Ty value.
   llvm::Value *EvaluateExprAsBool(const Expr *E);
 
+  /// Retrieve the implicit cast expression of the rhs in a binary operator
+  /// expression by passing pointers to Value and QualType
+  /// This is used for implicit bitfield conversion checks, which
+  /// must compare with the value before potential truncation.
+  llvm::Value *EmitWithOriginalRHSBitfieldAssignment(const BinaryOperator *E,
+                                                     llvm::Value *Previous,
+                                                     QualType *SrcType);
+
+  /// Emit a check that an [implicit] conversion of a bitfield. It is not UB,
+  /// so we use the value after conversion.
+  void EmitBitfieldConversionCheck(llvm::Value *Src, QualType SrcType,
+                                   llvm::Value *Dst, QualType DstType,
+                                   const CGBitFieldInfo &Info,
+                                   SourceLocation Loc);
+
   /// EmitIgnoredExpr - Emit an expression in a context which ignores the result.
   void EmitIgnoredExpr(const Expr *E);