llvmbot wrote:
<!--LLVM PR SUMMARY COMMENT--> @llvm/pr-subscribers-clang Author: Aaron Ballman (AaronBallman) <details> <summary>Changes</summary> Bit-fields of bit-precise integer type do not promote to int, but instead promote to the type of the field. Fixes #<!-- -->87641 --- Full diff: https://github.com/llvm/llvm-project/pull/89254.diff 3 Files Affected: - (modified) clang/docs/ReleaseNotes.rst (+3) - (modified) clang/lib/AST/ASTContext.cpp (+8) - (added) clang/test/Sema/bitint-bitfield-promote.c (+38) ``````````diff diff --git a/clang/docs/ReleaseNotes.rst b/clang/docs/ReleaseNotes.rst index 3fe15934323c53..1b5d69059230e6 100644 --- a/clang/docs/ReleaseNotes.rst +++ b/clang/docs/ReleaseNotes.rst @@ -179,6 +179,9 @@ C23 Feature Support - Clang now supports `N3018 The constexpr specifier for object definitions` <https://www.open-std.org/jtc1/sc22/wg14/www/docs/n3018.htm>`_. +- Properly promote bit-fields of bit-precise integer types to the field's type + rather than to ``int``. #GH87641 + Non-comprehensive list of changes in this release ------------------------------------------------- diff --git a/clang/lib/AST/ASTContext.cpp b/clang/lib/AST/ASTContext.cpp index b974fc28283c77..b36fb5523af5a6 100644 --- a/clang/lib/AST/ASTContext.cpp +++ b/clang/lib/AST/ASTContext.cpp @@ -7241,6 +7241,14 @@ QualType ASTContext::isPromotableBitField(Expr *E) const { // We perform that promotion here to match GCC and C++. // FIXME: C does not permit promotion of an enum bit-field whose rank is // greater than that of 'int'. We perform that promotion to match GCC. + // + // C23 6.3.1.1p2: + // The value from a bit-field of a bit-precise integer type is converted to + // the corresponding bit-precise integer type. (The rest is the same as in + // C11.) + if (QualType QT = Field->getType(); QT->isBitIntType()) + return QT; + if (BitWidth < IntSize) return IntTy; diff --git a/clang/test/Sema/bitint-bitfield-promote.c b/clang/test/Sema/bitint-bitfield-promote.c new file mode 100644 index 00000000000000..df09c40efca390 --- /dev/null +++ b/clang/test/Sema/bitint-bitfield-promote.c @@ -0,0 +1,38 @@ +// RUN: %clang_cc1 -fsyntax-only -verify -std=c23 %s + +// GH87641 noticed that integer promotion of a bit-field of bit-precise integer +// type was promoting to int rather than the type of the bit-field. +struct S { + unsigned _BitInt(7) x : 2; + unsigned _BitInt(2) y : 2; + unsigned _BitInt(72) z : 28; +}; + +// We don't have to worry about promotion cases where the bit-precise type is +// smaller than the width of the bit-field; that can't happen. +struct T { + unsigned _BitInt(28) oh_no : 72; // expected-error {{width of bit-field 'oh_no' (72 bits) exceeds the width of its type (28 bits)}} +}; + +static_assert( + _Generic(+(struct S){}.x, + int : 0, + unsigned _BitInt(7) : 1, + unsigned _BitInt(2) : 2 + ) == 1); + +static_assert( + _Generic(+(struct S){}.y, + int : 0, + unsigned _BitInt(7) : 1, + unsigned _BitInt(2) : 2 + ) == 2); + +static_assert( + _Generic(+(struct S){}.z, + int : 0, + unsigned _BitInt(72) : 1, + unsigned _BitInt(28) : 2 + ) == 1); + + `````````` </details> https://github.com/llvm/llvm-project/pull/89254 _______________________________________________ cfe-commits mailing list cfe-commits@lists.llvm.org https://lists.llvm.org/cgi-bin/mailman/listinfo/cfe-commits
