Fix bit-field promotion to be a bit closer to the behavior of gcc.
Patch by Enea Zaffanella, with some simplifications/corrections to
isPromotableBitField by me.
git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@79510 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/AST/ASTContext.cpp b/lib/AST/ASTContext.cpp
index 8a1f601..cf7ad26 100644
--- a/lib/AST/ASTContext.cpp
+++ b/lib/AST/ASTContext.cpp
@@ -2487,6 +2487,37 @@
}
}
+/// \brief Whether this is a promotable bitfield reference according
+/// to C99 6.3.1.1p2, bullet 2 (and GCC extensions).
+///
+/// \returns the type this bit-field will promote to, or NULL if no
+/// promotion occurs.
+QualType ASTContext::isPromotableBitField(Expr *E) {
+ FieldDecl *Field = E->getBitField();
+ if (!Field)
+ return QualType();
+
+ QualType FT = Field->getType();
+
+ llvm::APSInt BitWidthAP = Field->getBitWidth()->EvaluateAsInt(*this);
+ uint64_t BitWidth = BitWidthAP.getZExtValue();
+ uint64_t IntSize = getTypeSize(IntTy);
+ // GCC extension compatibility: if the bit-field size is less than or equal
+ // to the size of int, it gets promoted no matter what its type is.
+ // For instance, unsigned long bf : 4 gets promoted to signed int.
+ if (BitWidth < IntSize)
+ return IntTy;
+
+ if (BitWidth == IntSize)
+ return FT->isSignedIntegerType() ? IntTy : UnsignedIntTy;
+
+ // Types bigger than int are not subject to promotions, and therefore act
+ // like the base type.
+ // FIXME: This doesn't quite match what gcc does, but what gcc does here
+ // is ridiculous.
+ return QualType();
+}
+
/// getPromotedIntegerType - Returns the type that Promotable will
/// promote to: C99 6.3.1.1p2, assuming that Promotable is a promotable
/// integer type.