[PATCH] D145852: [Clang][AST] Fix __has_unique_object_representations computation for unnamed bitfields.

[Roy Jacobson via Phabricator via cfe-commits]

royjacobson updated this revision to Diff 504736.
royjacobson added a comment.

Add a test case, slightly simpler modeling.


Repository:
  rG LLVM Github Monorepo

CHANGES SINCE LAST ACTION
  https://reviews.llvm.org/D145852/new/

https://reviews.llvm.org/D145852

Files:
  clang/docs/ReleaseNotes.rst
  clang/lib/AST/ASTContext.cpp
  clang/test/SemaCXX/type-traits.cpp


Index: clang/test/SemaCXX/type-traits.cpp
===================================================================
--- clang/test/SemaCXX/type-traits.cpp
+++ clang/test/SemaCXX/type-traits.cpp
@@ -2878,9 +2878,29 @@
   char d : 2;
 };
 
+struct UnnamedBitfield {
+  int named : 8;
+  int : 24;
+};
+
+struct UnnamedEmptyBitfield {
+  int named;
+  int : 0;
+};
+
+struct UnnamedEmptyBitfieldSplit {
+  short named;
+  int : 0;
+  short also_named;
+};
+
 static_assert(!has_unique_object_representations<PaddedBitfield>::value, "Bitfield padding");
 static_assert(has_unique_object_representations<UnPaddedBitfield>::value, "Bitfield padding");
 static_assert(!has_unique_object_representations<AlignedPaddedBitfield>::value, "Bitfield padding");
+static_assert(!has_unique_object_representations<UnnamedBitfield>::value, "Bitfield padding");
+static_assert(has_unique_object_representations<UnnamedEmptyBitfield>::value, "Bitfield padding");
+static_assert(sizeof(UnnamedEmptyBitfieldSplit) != (sizeof(short) * 2), "Wrong size");
+static_assert(!has_unique_object_representations<UnnamedEmptyBitfieldSplit>::value, "Bitfield padding");
 
 struct BoolBitfield {
   bool b : 8;
Index: clang/lib/AST/ASTContext.cpp
===================================================================
--- clang/lib/AST/ASTContext.cpp
+++ clang/lib/AST/ASTContext.cpp
@@ -2810,6 +2810,11 @@
   int64_t FieldSizeInBits =
       Context.toBits(Context.getTypeSizeInChars(Field->getType()));
   if (Field->isBitField()) {
+    // If we have explicit padding bits, they don't contribute bits
+    // to the actual object representation, so return 0.
+    if (Field->isUnnamedBitfield())
+      return 0;
+
     int64_t BitfieldSize = Field->getBitWidthValue(Context);
     if (IsBitIntType) {
       if ((unsigned)BitfieldSize >
Index: clang/docs/ReleaseNotes.rst
===================================================================
--- clang/docs/ReleaseNotes.rst
+++ clang/docs/ReleaseNotes.rst
@@ -202,6 +202,9 @@
 - Fix crash when evaluating consteval constructor of derived class whose base
   has more than one field.
   (`#60166 <https://github.com/llvm/llvm-project/issues/60166>`_)
+- Fix bug in the computation of the ``__has_unique_object_representations``
+  builtin for types with unnamed bitfields.
+  (`#61336 <https://github.com/llvm/llvm-project/issues/61336>`_)
 
 Bug Fixes to AST Handling
 ^^^^^^^^^^^^^^^^^^^^^^^^^


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