[clang] b3e6ff3 - [clang-cl] Add support for [[msvc::constexpr]] C++11 attribute (#71300)
via cfe-commits
cfe-commits at lists.llvm.org
Sat Dec 9 02:35:43 PST 2023
Author: Richard Dzenis
Date: 2023-12-09T14:35:38+04:00
New Revision: b3e6ff331925dde24a4707452d657da0fdf7f588
URL: https://github.com/llvm/llvm-project/commit/b3e6ff331925dde24a4707452d657da0fdf7f588
DIFF: https://github.com/llvm/llvm-project/commit/b3e6ff331925dde24a4707452d657da0fdf7f588.diff
LOG: [clang-cl] Add support for [[msvc::constexpr]] C++11 attribute (#71300)
This commit introduces support for the MSVC-specific C++11-style
attribute `[[msvc::constexpr]]`, which was introduced in MSVC 14.33.
The semantics of this attribute are enabled only under
MSVC compatibility (`-fms-compatibility-version`) 14.33 and higher.
Additionally, the default value of `_MSC_VER` has been raised to 1433.
The current implementation lacks support for:
- `[[msvc::constexpr]]` constructors (see #72149);
at the time of this implementation, such support would have required
an unreasonable number of changes in Clang.
- `[[msvc::constexpr]] return ::new` (constexpr placement new) from
non-std namespaces (see #74924).
Relevant to: #57696
Added:
clang/test/AST/ms-constexpr.cpp
clang/test/SemaCXX/ms-constexpr-invalid.cpp
clang/test/SemaCXX/ms-constexpr-new.cpp
clang/test/SemaCXX/ms-constexpr.cpp
Modified:
clang/docs/ReleaseNotes.rst
clang/docs/UsersManual.rst
clang/include/clang/Basic/Attr.td
clang/include/clang/Basic/AttrDocs.td
clang/include/clang/Basic/DiagnosticSemaKinds.td
clang/include/clang/Basic/LangOptions.h
clang/lib/AST/ExprConstant.cpp
clang/lib/Basic/Targets/OSTargets.cpp
clang/lib/Driver/ToolChains/MSVC.cpp
clang/lib/Sema/SemaDecl.cpp
clang/lib/Sema/SemaDeclAttr.cpp
clang/lib/Sema/SemaStmtAttr.cpp
clang/test/Driver/cl-options.c
clang/test/Misc/pragma-attribute-supported-attributes-list.test
Removed:
################################################################################
diff --git a/clang/docs/ReleaseNotes.rst b/clang/docs/ReleaseNotes.rst
index 28f9393e28437d..b4b5352a306c1c 100644
--- a/clang/docs/ReleaseNotes.rst
+++ b/clang/docs/ReleaseNotes.rst
@@ -238,6 +238,8 @@ Non-comprehensive list of changes in this release
except that it returns the size of a type ignoring tail padding.
* ``__builtin_classify_type()`` now classifies ``_BitInt`` values as the return value ``18``
and vector types as return value ``19``, to match GCC 14's behavior.
+* The default value of `_MSC_VER` was raised from 1920 to 1933.
+* Since MSVC 19.33 added undocumented attribute ``[[msvc::constexpr]]``, this release adds the attribute as well.
* Added ``#pragma clang fp reciprocal``.
diff --git a/clang/docs/UsersManual.rst b/clang/docs/UsersManual.rst
index 9d64195ee338e2..f1b344ef5109b5 100644
--- a/clang/docs/UsersManual.rst
+++ b/clang/docs/UsersManual.rst
@@ -3359,8 +3359,8 @@ default for Windows targets.
For compatibility with existing code that compiles with MSVC, clang defines the
``_MSC_VER`` and ``_MSC_FULL_VER`` macros. When on Windows, these default to
-either the same value as the currently installed version of cl.exe, or ``1920``
-and ``192000000`` (respectively). The ``-fms-compatibility-version=`` flag
+either the same value as the currently installed version of cl.exe, or ``1933``
+and ``193300000`` (respectively). The ``-fms-compatibility-version=`` flag
overrides these values. It accepts a dotted version tuple, such as 19.00.23506.
Changing the MSVC compatibility version makes clang behave more like that
version of MSVC. For example, ``-fms-compatibility-version=19`` will enable
diff --git a/clang/include/clang/Basic/Attr.td b/clang/include/clang/Basic/Attr.td
index 121ed203829cec..b0a8ef10c500a7 100644
--- a/clang/include/clang/Basic/Attr.td
+++ b/clang/include/clang/Basic/Attr.td
@@ -3646,6 +3646,14 @@ def : MutualExclusions<[Owner, Pointer]>;
// Microsoft-related attributes
+def MSConstexpr : InheritableAttr {
+ let LangOpts = [MicrosoftExt];
+ let Spellings = [CXX11<"msvc", "constexpr">];
+ let Subjects = SubjectList<[Function, ReturnStmt], ErrorDiag,
+ "functions and return statements">;
+ let Documentation = [MSConstexprDocs];
+}
+
def MSNoVTable : InheritableAttr, TargetSpecificAttr<TargetMicrosoftCXXABI> {
let Spellings = [Declspec<"novtable">];
let Subjects = SubjectList<[CXXRecord]>;
diff --git a/clang/include/clang/Basic/AttrDocs.td b/clang/include/clang/Basic/AttrDocs.td
index 88f7c65e6e847b..1a98196834cefc 100644
--- a/clang/include/clang/Basic/AttrDocs.td
+++ b/clang/include/clang/Basic/AttrDocs.td
@@ -3657,6 +3657,21 @@ an error:
}];
}
+def MSConstexprDocs : Documentation {
+ let Category = DocCatStmt;
+ let Content = [{
+The ``[[msvc::constexpr]]`` attribute can be applied only to a function
+definition or a ``return`` statement. It does not impact function declarations.
+A ``[[msvc::constexpr]]`` function cannot be ``constexpr`` or ``consteval``.
+A ``[[msvc::constexpr]]`` function is treated as if it were a ``constexpr`` function
+when it is evaluated in a constant context of ``[[msvc::constexpr]] return`` statement.
+Otherwise, it is treated as a regular function.
+
+Semantics of this attribute are enabled only under MSVC compatibility
+(``-fms-compatibility-version``) 19.33 and later.
+ }];
+}
+
def MSNoVTableDocs : Documentation {
let Category = DocCatDecl;
let Content = [{
diff --git a/clang/include/clang/Basic/DiagnosticSemaKinds.td b/clang/include/clang/Basic/DiagnosticSemaKinds.td
index ea08fa84d022cd..28d95ca9b13893 100644
--- a/clang/include/clang/Basic/DiagnosticSemaKinds.td
+++ b/clang/include/clang/Basic/DiagnosticSemaKinds.td
@@ -2884,6 +2884,8 @@ def warn_cxx11_compat_constexpr_body_multiple_return : Warning<
InGroup<CXXPre14Compat>, DefaultIgnore;
def note_constexpr_body_previous_return : Note<
"previous return statement is here">;
+def err_ms_constexpr_cannot_be_applied : Error<
+ "attribute 'msvc::constexpr' cannot be applied to the %select{constexpr|consteval|virtual}0 function %1">;
// C++20 function try blocks in constexpr
def ext_constexpr_function_try_block_cxx20 : ExtWarn<
diff --git a/clang/include/clang/Basic/LangOptions.h b/clang/include/clang/Basic/LangOptions.h
index 2d167dd2bdf128..c4979b9a38c0cf 100644
--- a/clang/include/clang/Basic/LangOptions.h
+++ b/clang/include/clang/Basic/LangOptions.h
@@ -152,6 +152,7 @@ class LangOptions : public LangOptionsBase {
MSVC2019 = 1920,
MSVC2019_5 = 1925,
MSVC2019_8 = 1928,
+ MSVC2022_3 = 1933,
};
enum SYCLMajorVersion {
diff --git a/clang/lib/AST/ExprConstant.cpp b/clang/lib/AST/ExprConstant.cpp
index 986302e1fd225f..9bef70770a5449 100644
--- a/clang/lib/AST/ExprConstant.cpp
+++ b/clang/lib/AST/ExprConstant.cpp
@@ -641,6 +641,10 @@ namespace {
return false;
}
+ /// Whether we're in a context where [[msvc::constexpr]] evaluation is
+ /// permitted. See MSConstexprDocs for description of permitted contexts.
+ bool CanEvalMSConstexpr = false;
+
private:
APValue &createLocal(APValue::LValueBase Base, const void *Key, QualType T,
ScopeKind Scope);
@@ -674,6 +678,19 @@ namespace {
private:
llvm::TimeTraceScope TimeScope;
};
+
+ /// RAII object used to change the current ability of
+ /// [[msvc::constexpr]] evaulation.
+ struct MSConstexprContextRAII {
+ CallStackFrame &Frame;
+ bool OldValue;
+ explicit MSConstexprContextRAII(CallStackFrame &Frame, bool Value)
+ : Frame(Frame), OldValue(Frame.CanEvalMSConstexpr) {
+ Frame.CanEvalMSConstexpr = Value;
+ }
+
+ ~MSConstexprContextRAII() { Frame.CanEvalMSConstexpr = OldValue; }
+ };
}
static bool HandleDestruction(EvalInfo &Info, const Expr *E,
@@ -5546,11 +5563,14 @@ static EvalStmtResult EvaluateStmt(StmtResult &Result, EvalInfo &Info,
case Stmt::LabelStmtClass:
return EvaluateStmt(Result, Info, cast<LabelStmt>(S)->getSubStmt(), Case);
- case Stmt::AttributedStmtClass:
- // As a general principle, C++11 attributes can be ignored without
- // any semantic impact.
- return EvaluateStmt(Result, Info, cast<AttributedStmt>(S)->getSubStmt(),
- Case);
+ case Stmt::AttributedStmtClass: {
+ const auto *AS = cast<AttributedStmt>(S);
+ const auto *SS = AS->getSubStmt();
+ MSConstexprContextRAII ConstexprContext(
+ *Info.CurrentCall, hasSpecificAttr<MSConstexprAttr>(AS->getAttrs()) &&
+ isa<ReturnStmt>(SS));
+ return EvaluateStmt(Result, Info, SS, Case);
+ }
case Stmt::CaseStmtClass:
case Stmt::DefaultStmtClass:
@@ -5621,7 +5641,9 @@ static bool CheckConstexprFunction(EvalInfo &Info, SourceLocation CallLoc,
}
// Can we evaluate this function call?
- if (Definition && Definition->isConstexpr() && Body)
+ if (Definition && Body &&
+ (Definition->isConstexpr() || Info.CurrentCall->CanEvalMSConstexpr &&
+ Definition->hasAttr<MSConstexprAttr>()))
return true;
if (Info.getLangOpts().CPlusPlus11) {
diff --git a/clang/lib/Basic/Targets/OSTargets.cpp b/clang/lib/Basic/Targets/OSTargets.cpp
index 627bc912fa2310..899aefa6173acf 100644
--- a/clang/lib/Basic/Targets/OSTargets.cpp
+++ b/clang/lib/Basic/Targets/OSTargets.cpp
@@ -224,6 +224,9 @@ static void addVisualCDefines(const LangOptions &Opts, MacroBuilder &Builder) {
else if (Opts.CPlusPlus14)
Builder.defineMacro("_MSVC_LANG", "201402L");
}
+
+ if (Opts.isCompatibleWithMSVC(LangOptions::MSVC2022_3))
+ Builder.defineMacro("_MSVC_CONSTEXPR_ATTRIBUTE");
}
if (Opts.MicrosoftExt) {
diff --git a/clang/lib/Driver/ToolChains/MSVC.cpp b/clang/lib/Driver/ToolChains/MSVC.cpp
index 8a4a174c90ea85..6d925555b7bb4b 100644
--- a/clang/lib/Driver/ToolChains/MSVC.cpp
+++ b/clang/lib/Driver/ToolChains/MSVC.cpp
@@ -787,11 +787,11 @@ VersionTuple MSVCToolChain::computeMSVCVersion(const Driver *D,
if (MSVT.empty() &&
Args.hasFlag(options::OPT_fms_extensions, options::OPT_fno_ms_extensions,
IsWindowsMSVC)) {
- // -fms-compatibility-version=19.20 is default, aka 2019, 16.x
+ // -fms-compatibility-version=19.33 is default, aka 2022, 17.3
// NOTE: when changing this value, also update
// clang/docs/CommandGuide/clang.rst and clang/docs/UsersManual.rst
// accordingly.
- MSVT = VersionTuple(19, 20);
+ MSVT = VersionTuple(19, 33);
}
return MSVT;
}
diff --git a/clang/lib/Sema/SemaDecl.cpp b/clang/lib/Sema/SemaDecl.cpp
index 7650589608c5f4..19d972ed8ab2d8 100644
--- a/clang/lib/Sema/SemaDecl.cpp
+++ b/clang/lib/Sema/SemaDecl.cpp
@@ -16221,7 +16221,9 @@ Decl *Sema::ActOnFinishFunctionBody(Decl *dcl, Stmt *Body,
ActivePolicy = &WP;
}
- if (!IsInstantiation && FD && FD->isConstexpr() && !FD->isInvalidDecl() &&
+ if (!IsInstantiation && FD &&
+ (FD->isConstexpr() || FD->hasAttr<MSConstexprAttr>()) &&
+ !FD->isInvalidDecl() &&
!CheckConstexprFunctionDefinition(FD, CheckConstexprKind::Diagnose))
FD->setInvalidDecl();
diff --git a/clang/lib/Sema/SemaDeclAttr.cpp b/clang/lib/Sema/SemaDeclAttr.cpp
index a345978bb8701c..59e456fd9f7298 100644
--- a/clang/lib/Sema/SemaDeclAttr.cpp
+++ b/clang/lib/Sema/SemaDeclAttr.cpp
@@ -7372,6 +7372,28 @@ static void handleDeclspecThreadAttr(Sema &S, Decl *D, const ParsedAttr &AL) {
D->addAttr(::new (S.Context) ThreadAttr(S.Context, AL));
}
+static void handleMSConstexprAttr(Sema &S, Decl *D, const ParsedAttr &AL) {
+ if (!S.getLangOpts().isCompatibleWithMSVC(LangOptions::MSVC2022_3)) {
+ S.Diag(AL.getLoc(), diag::warn_unknown_attribute_ignored)
+ << AL << AL.getRange();
+ return;
+ }
+ auto *FD = cast<FunctionDecl>(D);
+ if (FD->isConstexprSpecified() || FD->isConsteval()) {
+ S.Diag(AL.getLoc(), diag::err_ms_constexpr_cannot_be_applied)
+ << FD->isConsteval() << FD;
+ return;
+ }
+ if (auto *MD = dyn_cast<CXXMethodDecl>(FD)) {
+ if (!S.getLangOpts().CPlusPlus20 && MD->isVirtual()) {
+ S.Diag(AL.getLoc(), diag::err_ms_constexpr_cannot_be_applied)
+ << /*virtual*/ 2 << MD;
+ return;
+ }
+ }
+ D->addAttr(::new (S.Context) MSConstexprAttr(S.Context, AL));
+}
+
static void handleAbiTagAttr(Sema &S, Decl *D, const ParsedAttr &AL) {
SmallVector<StringRef, 4> Tags;
for (unsigned I = 0, E = AL.getNumArgs(); I != E; ++I) {
@@ -9477,6 +9499,9 @@ ProcessDeclAttribute(Sema &S, Scope *scope, Decl *D, const ParsedAttr &AL,
case ParsedAttr::AT_Thread:
handleDeclspecThreadAttr(S, D, AL);
break;
+ case ParsedAttr::AT_MSConstexpr:
+ handleMSConstexprAttr(S, D, AL);
+ break;
// HLSL attributes:
case ParsedAttr::AT_HLSLNumThreads:
diff --git a/clang/lib/Sema/SemaStmtAttr.cpp b/clang/lib/Sema/SemaStmtAttr.cpp
index eae1eaa2f9563d..725d8efe3828d6 100644
--- a/clang/lib/Sema/SemaStmtAttr.cpp
+++ b/clang/lib/Sema/SemaStmtAttr.cpp
@@ -397,6 +397,16 @@ static void CheckForDuplicateCodeAlignAttrs(Sema &S,
}
}
+static Attr *handleMSConstexprAttr(Sema &S, Stmt *St, const ParsedAttr &A,
+ SourceRange Range) {
+ if (!S.getLangOpts().isCompatibleWithMSVC(LangOptions::MSVC2022_3)) {
+ S.Diag(A.getLoc(), diag::warn_unknown_attribute_ignored)
+ << A << A.getRange();
+ return nullptr;
+ }
+ return ::new (S.Context) MSConstexprAttr(S.Context, A);
+}
+
#define WANT_STMT_MERGE_LOGIC
#include "clang/Sema/AttrParsedAttrImpl.inc"
#undef WANT_STMT_MERGE_LOGIC
@@ -600,6 +610,8 @@ static Attr *ProcessStmtAttribute(Sema &S, Stmt *St, const ParsedAttr &A,
return handleUnlikely(S, St, A, Range);
case ParsedAttr::AT_CodeAlign:
return handleCodeAlignAttr(S, St, A);
+ case ParsedAttr::AT_MSConstexpr:
+ return handleMSConstexprAttr(S, St, A, Range);
default:
// N.B., ClangAttrEmitter.cpp emits a diagnostic helper that ensures a
// declaration attribute is not written on a statement, but this code is
diff --git a/clang/test/AST/ms-constexpr.cpp b/clang/test/AST/ms-constexpr.cpp
new file mode 100644
index 00000000000000..e85af8494f3344
--- /dev/null
+++ b/clang/test/AST/ms-constexpr.cpp
@@ -0,0 +1,28 @@
+// RUN: %clang_cc1 -fms-compatibility -fms-compatibility-version=19.33 -std=c++20 -ast-dump -verify %s | FileCheck %s
+// expected-no-diagnostics
+
+// CHECK: used f1 'bool ()'
+// CHECK: MSConstexprAttr 0x{{[0-9a-f]+}} <col:3, col:9>
+[[msvc::constexpr]] bool f1() { return true; }
+
+// CHECK: used constexpr f2 'bool ()'
+// CHECK-NEXT: CompoundStmt 0x{{[0-9a-f]+}} <col:21, col:56>
+// CHECK-NEXT: AttributedStmt 0x{{[0-9a-f]+}} <col:23, col:53>
+// CHECK-NEXT: MSConstexprAttr 0x{{[0-9a-f]+}} <col:25, col:31>
+// CHECK-NEXT: ReturnStmt 0x{{[0-9a-f]+}} <col:43, col:53>
+constexpr bool f2() { [[msvc::constexpr]] return f1(); }
+static_assert(f2());
+
+struct S1 {
+ // CHECK: used vm 'bool ()' virtual
+ // CHECK: MSConstexprAttr 0x{{[0-9a-f]+}} <col:7, col:13>
+ [[msvc::constexpr]] virtual bool vm() { return true; }
+
+ // CHECK: used constexpr cm 'bool ()'
+ // CHECK-NEXT: CompoundStmt 0x{{[0-9a-f]+}} <col:25, col:60>
+ // CHECK-NEXT: AttributedStmt 0x{{[0-9a-f]+}} <col:27, col:57>
+ // CHECK-NEXT: MSConstexprAttr 0x{{[0-9a-f]+}} <col:29, col:35>
+ // CHECK-NEXT: ReturnStmt 0x{{[0-9a-f]+}} <col:47, col:57>
+ constexpr bool cm() { [[msvc::constexpr]] return vm(); }
+};
+static_assert(S1{}.cm());
diff --git a/clang/test/Driver/cl-options.c b/clang/test/Driver/cl-options.c
index 6d929b19e7e2ef..81d1b907eced18 100644
--- a/clang/test/Driver/cl-options.c
+++ b/clang/test/Driver/cl-options.c
@@ -747,7 +747,7 @@
// Validate that the default triple is used when run an empty tools dir is specified
// RUN: %clang_cl -vctoolsdir "" -### -- %s 2>&1 | FileCheck %s --check-prefix VCTOOLSDIR
-// VCTOOLSDIR: "-triple" "{{[a-zA-Z0-9_-]*}}-pc-windows-msvc19.20.0"
+// VCTOOLSDIR: "-triple" "{{[a-zA-Z0-9_-]*}}-pc-windows-msvc19.33.0"
// Validate that built-in include paths are based on the supplied path
// RUN: %clang_cl --target=aarch64-pc-windows-msvc -vctoolsdir "/fake" -winsdkdir "/foo" -winsdkversion 10.0.12345.0 -### -- %s 2>&1 | FileCheck %s --check-prefix FAKEDIR
@@ -787,7 +787,7 @@
// RUN: %clang_cl -vctoolsdir "" /arm64EC /c -### -- %s 2>&1 | FileCheck --check-prefix=ARM64EC %s
// ARM64EC-NOT: /arm64EC has been overridden by specified target
-// ARM64EC: "-triple" "arm64ec-pc-windows-msvc19.20.0"
+// ARM64EC: "-triple" "arm64ec-pc-windows-msvc19.33.0"
// RUN: %clang_cl -vctoolsdir "" /arm64EC /c -target x86_64-pc-windows-msvc -### -- %s 2>&1 | FileCheck --check-prefix=ARM64EC_OVERRIDE %s
// ARM64EC_OVERRIDE: warning: /arm64EC has been overridden by specified target: x86_64-pc-windows-msvc; option ignored
diff --git a/clang/test/Misc/pragma-attribute-supported-attributes-list.test b/clang/test/Misc/pragma-attribute-supported-attributes-list.test
index 707fc8875089f7..bdfda430eea86c 100644
--- a/clang/test/Misc/pragma-attribute-supported-attributes-list.test
+++ b/clang/test/Misc/pragma-attribute-supported-attributes-list.test
@@ -90,6 +90,7 @@
// CHECK-NEXT: LoaderUninitialized (SubjectMatchRule_variable_is_global)
// CHECK-NEXT: Lockable (SubjectMatchRule_record)
// CHECK-NEXT: MIGServerRoutine (SubjectMatchRule_function, SubjectMatchRule_objc_method, SubjectMatchRule_block)
+// CHECK-NEXT: MSConstexpr (SubjectMatchRule_function)
// CHECK-NEXT: MSStruct (SubjectMatchRule_record)
// CHECK-NEXT: MaybeUndef (SubjectMatchRule_variable_is_parameter)
// CHECK-NEXT: MicroMips (SubjectMatchRule_function)
diff --git a/clang/test/SemaCXX/ms-constexpr-invalid.cpp b/clang/test/SemaCXX/ms-constexpr-invalid.cpp
new file mode 100644
index 00000000000000..e5bec0c7119b02
--- /dev/null
+++ b/clang/test/SemaCXX/ms-constexpr-invalid.cpp
@@ -0,0 +1,52 @@
+// RUN: %clang_cc1 -fms-compatibility -fms-compatibility-version=19.33 -std=c++20 -verify %s
+// RUN: %clang_cc1 -fms-compatibility -fms-compatibility-version=19.33 -std=c++17 -verify %s
+
+// Check explicitly invalid code
+
+void runtime() {} // expected-note {{declared here}}
+
+[[msvc::constexpr]] void f0() { runtime(); } // expected-error {{constexpr function never produces a constant expression}} \
+ // expected-note {{non-constexpr function 'runtime' cannot be used in a constant expression}}
+[[msvc::constexpr]] constexpr void f1() {} // expected-error {{attribute 'msvc::constexpr' cannot be applied to the constexpr function 'f1'}}
+#if __cplusplus >= 202202L
+[[msvc::constexpr]] consteval void f2() {} // expected-error {{attribute 'msvc::constexpr' cannot be applied to the consteval function 'f1'}}
+#endif
+
+struct B1 {};
+struct D1 : virtual B1 { // expected-note {{virtual base class declared here}}
+ [[msvc::constexpr]] D1() {} // expected-error {{constexpr constructor not allowed in struct with virtual base class}}
+};
+
+struct [[msvc::constexpr]] S2{}; // expected-error {{'constexpr' attribute only applies to functions and return statements}}
+
+// Check invalid code mixed with valid code
+
+[[msvc::constexpr]] int f4(int x) { return x > 1 ? 1 + f4(x / 2) : 0; } // expected-note {{non-constexpr function 'f4' cannot be used in a constant expression}} \
+ // expected-note {{declared here}} \
+ // expected-note {{declared here}} \
+ // expected-note {{declared here}}
+constexpr bool f5() { [[msvc::constexpr]] return f4(32) == 5; } // expected-note {{in call to 'f4(32)'}}
+static_assert(f5()); // expected-error {{static assertion expression is not an integral constant expression}} \
+ // expected-note {{in call to 'f5()'}}
+
+int f6(int x) { [[msvc::constexpr]] return x > 1 ? 1 + f6(x / 2) : 0; } // expected-note {{declared here}} \
+ // expected-note {{declared here}}
+constexpr bool f7() { [[msvc::constexpr]] return f6(32) == 5; } // expected-error {{constexpr function never produces a constant expression}} \
+ // expected-note {{non-constexpr function 'f6' cannot be used in a constant expression}} \
+ // expected-note {{non-constexpr function 'f6' cannot be used in a constant expression}}
+static_assert(f7()); // expected-error {{static assertion expression is not an integral constant expression}} \
+ // expected-note {{in call to 'f7()'}}
+
+constexpr bool f8() { // expected-error {{constexpr function never produces a constant expression}}
+ [[msvc::constexpr]] f4(32); // expected-error {{'constexpr' attribute only applies to functions and return statements}} \
+ // expected-note {{non-constexpr function 'f4' cannot be used in a constant expression}} \
+ // expected-note {{non-constexpr function 'f4' cannot be used in a constant expression}}
+ [[msvc::constexpr]] int i5 = f4(32); // expected-error {{'constexpr' attribute only applies to functions and return statements}}
+ return i5 == 5;
+}
+static_assert(f8()); // expected-error {{static assertion expression is not an integral constant expression}} \
+ // expected-note {{in call to 'f8()'}}
+
+#if __cplusplus == 201702L
+struct S1 { [[msvc::constexpr]] virtual bool vm() const { return true; } }; // expected-error {{attribute 'msvc::constexpr' ignored, it only applies to function definitions and return statements}}
+#endif
diff --git a/clang/test/SemaCXX/ms-constexpr-new.cpp b/clang/test/SemaCXX/ms-constexpr-new.cpp
new file mode 100644
index 00000000000000..05ee5c5b4e154a
--- /dev/null
+++ b/clang/test/SemaCXX/ms-constexpr-new.cpp
@@ -0,0 +1,16 @@
+// RUN: %clang_cc1 -fms-compatibility -fms-compatibility-version=19.33 -std=c++20 -verify=supported %s
+// RUN: %clang_cc1 -fms-compatibility -fms-compatibility-version=19.32 -std=c++20 -verify=unsupported %s
+// supported-no-diagnostics
+
+[[nodiscard]]
+[[msvc::constexpr]] // unsupported-warning {{unknown attribute 'constexpr' ignored}}
+inline void* __cdecl operator new(decltype(sizeof(void*)), void* p) noexcept { return p; }
+
+namespace std {
+ constexpr int* construct_at(int* p, int v) {
+ [[msvc::constexpr]] return ::new (p) int(v); // unsupported-warning {{unknown attribute 'constexpr' ignored}}
+ }
+}
+
+constexpr bool check_construct_at() { int x; return *std::construct_at(&x, 42) == 42; }
+static_assert(check_construct_at());
diff --git a/clang/test/SemaCXX/ms-constexpr.cpp b/clang/test/SemaCXX/ms-constexpr.cpp
new file mode 100644
index 00000000000000..79f71a34cb7d84
--- /dev/null
+++ b/clang/test/SemaCXX/ms-constexpr.cpp
@@ -0,0 +1,37 @@
+// RUN: %clang_cc1 -fms-compatibility -fms-compatibility-version=19.33 -std=c++20 -verify %s
+
+[[msvc::constexpr]] int log2(int x) { [[msvc::constexpr]] return x > 1 ? 1 + log2(x / 2) : 0; }
+constexpr bool test_log2() { [[msvc::constexpr]] return log2(32) == 5; }
+static_assert(test_log2());
+
+[[msvc::constexpr]] int get_value(int x)
+{
+ switch (x)
+ {
+ case 42: return 1337;
+ default:
+ if (x < 0) [[msvc::constexpr]] return log2(-x);
+ else return x;
+ }
+}
+
+constexpr bool test_complex_expr() {
+ [[msvc::constexpr]] return get_value(get_value(42) - 1337 + get_value(-32) - 5 + (get_value(1) ? get_value(0) : get_value(2))) == get_value(0);
+}
+static_assert(test_complex_expr());
+
+constexpr bool get_constexpr_true() { return true; }
+[[msvc::constexpr]] bool get_msconstexpr_true() { return get_constexpr_true(); }
+constexpr bool test_get_msconstexpr_true() { [[msvc::constexpr]] return get_msconstexpr_true(); }
+static_assert(test_get_msconstexpr_true());
+
+// TODO (#72149): Add support for [[msvc::constexpr]] constructor; this code is valid for MSVC.
+struct S2 {
+ [[msvc::constexpr]] S2() {}
+ [[msvc::constexpr]] bool value() { return true; }
+ static constexpr bool check() { [[msvc::constexpr]] return S2{}.value(); } // expected-error {{constexpr function never produces a constant expression}} \
+ // expected-note {{non-literal type 'S2' cannot be used in a constant expression}} \
+ // expected-note {{non-literal type 'S2' cannot be used in a constant expression}}
+};
+static_assert(S2::check()); // expected-error {{static assertion expression is not an integral constant expression}} \
+ // expected-note {{in call to 'check()'}}
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