This revision was automatically updated to reflect the committed changes.
Closed by commit rG9523cf02c22a: [AST] Fix handling of long double and bool in
__builtin_bit_cast (authored by erik.pilkington).
Herald added a project: clang.
Repository:
rG LLVM Github Monorepo
CHANGES SINCE LAST ACTION
https://reviews.llvm.org/D76323/new/
https://reviews.llvm.org/D76323
Files:
clang/include/clang/Basic/DiagnosticASTKinds.td
clang/lib/AST/ExprConstant.cpp
clang/test/SemaCXX/constexpr-builtin-bit-cast.cpp
Index: clang/test/SemaCXX/constexpr-builtin-bit-cast.cpp
===================================================================
--- clang/test/SemaCXX/constexpr-builtin-bit-cast.cpp
+++ clang/test/SemaCXX/constexpr-builtin-bit-cast.cpp
@@ -23,6 +23,10 @@
template <class To, class From>
constexpr To bit_cast(const From &from) {
static_assert(sizeof(To) == sizeof(From));
+ // expected-note@+9 {{cannot be represented in type 'bool'}}
+#ifdef __x86_64
+ // expected-note@+7 {{or 'std::byte'; '__int128' is invalid}}
+#endif
#ifdef __CHAR_UNSIGNED__
// expected-note@+4 2 {{indeterminate value can only initialize an object of type 'unsigned char', 'char', or 'std::byte'; 'signed char' is invalid}}
#else
@@ -397,3 +401,65 @@
};
constexpr IdentityInUnion identity3a = {42};
constexpr unsigned char identity3b = __builtin_bit_cast(unsigned char, identity3a.n);
+
+namespace test_bool {
+
+constexpr bool test_bad_bool = bit_cast<bool>('A'); // expected-error {{must be initialized by a constant expression}} expected-note{{in call}}
+
+static_assert(round_trip<signed char>(true), "");
+static_assert(round_trip<unsigned char>(false), "");
+static_assert(round_trip<bool>(false), "");
+
+static_assert(round_trip<bool>((char)0), "");
+static_assert(round_trip<bool>((char)1), "");
+}
+
+namespace test_long_double {
+#ifdef __x86_64
+constexpr __int128_t test_cast_to_int128 = bit_cast<__int128_t>((long double)0); // expected-error{{must be initialized by a constant expression}} expected-note{{in call}}
+
+constexpr long double ld = 3.1425926539;
+
+struct bytes {
+ unsigned char d[16];
+};
+
+static_assert(round_trip<bytes>(ld), "");
+
+static_assert(round_trip<long double>(10.0L));
+
+constexpr bool f(bool read_uninit) {
+ bytes b = bit_cast<bytes>(ld);
+ unsigned char ld_bytes[10] = {
+ 0x0, 0x48, 0x9f, 0x49, 0xf0,
+ 0x3c, 0x20, 0xc9, 0x0, 0x40,
+ };
+
+ for (int i = 0; i != 10; ++i)
+ if (ld_bytes[i] != b.d[i])
+ return false;
+
+ if (read_uninit && b.d[10]) // expected-note{{read of uninitialized object is not allowed in a constant expression}}
+ return false;
+
+ return true;
+}
+
+static_assert(f(/*read_uninit=*/false), "");
+static_assert(f(/*read_uninit=*/true), ""); // expected-error{{static_assert expression is not an integral constant expression}} expected-note{{in call to 'f(true)'}}
+
+constexpr bytes ld539 = {
+ 0x0, 0x0, 0x0, 0x0,
+ 0x0, 0x0, 0xc0, 0x86,
+ 0x8, 0x40, 0x0, 0x0,
+ 0x0, 0x0, 0x0, 0x0,
+};
+
+constexpr long double fivehundredandthirtynine = 539.0;
+
+static_assert(bit_cast<long double>(ld539) == fivehundredandthirtynine, "");
+
+#else
+static_assert(round_trip<__int128_t>(34.0L));
+#endif
+}
Index: clang/lib/AST/ExprConstant.cpp
===================================================================
--- clang/lib/AST/ExprConstant.cpp
+++ clang/lib/AST/ExprConstant.cpp
@@ -6627,9 +6627,15 @@
}
bool visitInt(const APSInt &Val, QualType Ty, CharUnits Offset) {
- CharUnits Width = Info.Ctx.getTypeSizeInChars(Ty);
- SmallVector<unsigned char, 8> Bytes(Width.getQuantity());
- llvm::StoreIntToMemory(Val, &*Bytes.begin(), Width.getQuantity());
+ APSInt AdjustedVal = Val;
+ unsigned Width = AdjustedVal.getBitWidth();
+ if (Ty->isBooleanType()) {
+ Width = Info.Ctx.getTypeSize(Ty);
+ AdjustedVal = AdjustedVal.extend(Width);
+ }
+
+ SmallVector<unsigned char, 8> Bytes(Width / 8);
+ llvm::StoreIntToMemory(AdjustedVal, &*Bytes.begin(), Width / 8);
Buffer.writeObject(Offset, Bytes);
return true;
}
@@ -6670,6 +6676,13 @@
return None;
}
+ llvm::NoneType unrepresentableValue(QualType Ty, const APSInt &Val) {
+ Info.FFDiag(BCE->getBeginLoc(),
+ diag::note_constexpr_bit_cast_unrepresentable_value)
+ << Ty << Val.toString(/*Radix=*/10);
+ return None;
+ }
+
Optional<APValue> visit(const BuiltinType *T, CharUnits Offset,
const EnumType *EnumSugar = nullptr) {
if (T->isNullPtrType()) {
@@ -6680,6 +6693,20 @@
}
CharUnits SizeOf = Info.Ctx.getTypeSizeInChars(T);
+
+ // Work around floating point types that contain unused padding bytes. This
+ // is really just `long double` on x86, which is the only fundamental type
+ // with padding bytes.
+ if (T->isRealFloatingType()) {
+ const llvm::fltSemantics &Semantics =
+ Info.Ctx.getFloatTypeSemantics(QualType(T, 0));
+ unsigned NumBits = llvm::APFloatBase::getSizeInBits(Semantics);
+ assert(NumBits % 8 == 0);
+ CharUnits NumBytes = CharUnits::fromQuantity(NumBits / 8);
+ if (NumBytes != SizeOf)
+ SizeOf = NumBytes;
+ }
+
SmallVector<uint8_t, 8> Bytes;
if (!Buffer.readObject(Offset, SizeOf, Bytes)) {
// If this is std::byte or unsigned char, then its okay to store an
@@ -6704,6 +6731,15 @@
if (T->isIntegralOrEnumerationType()) {
Val.setIsSigned(T->isSignedIntegerOrEnumerationType());
+
+ unsigned IntWidth = Info.Ctx.getIntWidth(QualType(T, 0));
+ if (IntWidth != Val.getBitWidth()) {
+ APSInt Truncated = Val.trunc(IntWidth);
+ if (Truncated.extend(Val.getBitWidth()) != Val)
+ return unrepresentableValue(QualType(T, 0), Val);
+ Val = Truncated;
+ }
+
return APValue(Val);
}
Index: clang/include/clang/Basic/DiagnosticASTKinds.td
===================================================================
--- clang/include/clang/Basic/DiagnosticASTKinds.td
+++ clang/include/clang/Basic/DiagnosticASTKinds.td
@@ -298,6 +298,8 @@
def note_constexpr_bit_cast_indet_dest : Note<
"indeterminate value can only initialize an object of type 'unsigned char'"
"%select{, 'char',|}1 or 'std::byte'; %0 is invalid">;
+def note_constexpr_bit_cast_unrepresentable_value : Note<
+ "value %1 cannot be represented in type %0">;
def note_constexpr_pseudo_destructor : Note<
"pseudo-destructor call is not permitted in constant expressions "
"until C++20">;
_______________________________________________
cfe-commits mailing list
cfe-commits@lists.llvm.org
https://lists.llvm.org/cgi-bin/mailman/listinfo/cfe-commits
