https://github.com/MitalAshok created
https://github.com/llvm/llvm-project/pull/91894
Also support redeclaring now-constexpr builtins without constexpr
>From 56aed689dc5825fc5bacc6dfdff58ee0eaf71f82 Mon Sep 17 00:00:00 2001
From: Mital Ashok <mi...@mitalashok.co.uk>
Date: Sun, 12 May 2024 19:48:24 +0100
Subject: [PATCH] [Clang] Add attribute for consteval builtins; Declare
constexpr builtins as constexpr in C++
Also support redeclaring now-constexpr builtins without constexpr
---
clang/include/clang/Basic/Builtins.h | 5 +++++
clang/include/clang/Basic/BuiltinsBase.td | 2 ++
clang/lib/Sema/SemaDecl.cpp | 15 +++++++++++----
clang/lib/Sema/SemaDeclCXX.cpp | 18 +++++++++++++-----
clang/lib/Sema/SemaExpr.cpp | 8 ++++++--
clang/test/Sema/builtin-redecl.cpp | 15 ++++++++++-----
6 files changed, 47 insertions(+), 16 deletions(-)
diff --git a/clang/include/clang/Basic/Builtins.h
b/clang/include/clang/Basic/Builtins.h
index f955d21169556..e85ec5b2dca14 100644
--- a/clang/include/clang/Basic/Builtins.h
+++ b/clang/include/clang/Basic/Builtins.h
@@ -280,6 +280,11 @@ class Context {
return strchr(getRecord(ID).Attributes, 'E') != nullptr;
}
+ /// Returns true if this is an immediate (consteval) function
+ bool isImmediate(unsigned ID) const {
+ return strchr(getRecord(ID).Attributes, 'G') != nullptr;
+ }
+
private:
const Info &getRecord(unsigned ID) const;
diff --git a/clang/include/clang/Basic/BuiltinsBase.td
b/clang/include/clang/Basic/BuiltinsBase.td
index 724747ec76d73..1196b9e15c10d 100644
--- a/clang/include/clang/Basic/BuiltinsBase.td
+++ b/clang/include/clang/Basic/BuiltinsBase.td
@@ -70,6 +70,8 @@ class VScanfFormat<int I> : IndexedAttribute<"S", I>;
// Builtin can be constant evaluated
def Constexpr : Attribute<"E">;
+// Builtin is immediate and must be constant evaluated. Implies Constexpr.
+def Consteval : Attribute<"EG">;
// Builtin kinds
// =============
diff --git a/clang/lib/Sema/SemaDecl.cpp b/clang/lib/Sema/SemaDecl.cpp
index fb913034bd836..6b0a04585928a 100644
--- a/clang/lib/Sema/SemaDecl.cpp
+++ b/clang/lib/Sema/SemaDecl.cpp
@@ -2409,10 +2409,17 @@ FunctionDecl *Sema::CreateBuiltin(IdentifierInfo *II,
QualType Type,
Parent = CLinkageDecl;
}
- FunctionDecl *New = FunctionDecl::Create(Context, Parent, Loc, Loc, II, Type,
- /*TInfo=*/nullptr, SC_Extern,
-
getCurFPFeatures().isFPConstrained(),
- false, Type->isFunctionProtoType());
+ ConstexprSpecKind ConstexprKind = ConstexprSpecKind::Unspecified;
+ if (getLangOpts().CPlusPlus && Context.BuiltinInfo.isConstantEvaluated(ID)) {
+ ConstexprKind = ConstexprSpecKind::Constexpr;
+ if (Context.BuiltinInfo.isImmediate(ID))
+ ConstexprKind = ConstexprSpecKind::Consteval;
+ }
+
+ FunctionDecl *New = FunctionDecl::Create(
+ Context, Parent, Loc, Loc, II, Type, /*TInfo=*/nullptr, SC_Extern,
+ getCurFPFeatures().isFPConstrained(), /*isInlineSpecified=*/false,
+ Type->isFunctionProtoType(), ConstexprKind);
New->setImplicit();
New->addAttr(BuiltinAttr::CreateImplicit(Context, ID));
diff --git a/clang/lib/Sema/SemaDeclCXX.cpp b/clang/lib/Sema/SemaDeclCXX.cpp
index 53238d355ea09..1b558d70f9b48 100644
--- a/clang/lib/Sema/SemaDeclCXX.cpp
+++ b/clang/lib/Sema/SemaDeclCXX.cpp
@@ -676,11 +676,19 @@ bool Sema::MergeCXXFunctionDecl(FunctionDecl *New,
FunctionDecl *Old,
// template has a constexpr specifier then all its declarations shall
// contain the constexpr specifier.
if (New->getConstexprKind() != Old->getConstexprKind()) {
- Diag(New->getLocation(), diag::err_constexpr_redecl_mismatch)
- << New << static_cast<int>(New->getConstexprKind())
- << static_cast<int>(Old->getConstexprKind());
- Diag(Old->getLocation(), diag::note_previous_declaration);
- Invalid = true;
+ if (Old->getBuiltinID() &&
+ Old->getConstexprKind() == ConstexprSpecKind::Constexpr &&
+ New->getConstexprKind() == ConstexprSpecKind::Unspecified) {
+ // Except allow redeclaring a builtin as non-constexpr to match C
+ // redeclarations which will not be constexpr
+ New->setConstexprKind(ConstexprSpecKind::Constexpr);
+ } else {
+ Diag(New->getLocation(), diag::err_constexpr_redecl_mismatch)
+ << New << static_cast<int>(New->getConstexprKind())
+ << static_cast<int>(Old->getConstexprKind());
+ Diag(Old->getLocation(), diag::note_previous_declaration);
+ Invalid = true;
+ }
} else if (!Old->getMostRecentDecl()->isInlined() && New->isInlined() &&
Old->isDefined(Def) &&
// If a friend function is inlined but does not have 'inline'
diff --git a/clang/lib/Sema/SemaExpr.cpp b/clang/lib/Sema/SemaExpr.cpp
index bb4b116fd73ca..39aa32526d2b1 100644
--- a/clang/lib/Sema/SemaExpr.cpp
+++ b/clang/lib/Sema/SemaExpr.cpp
@@ -7095,8 +7095,12 @@ ExprResult Sema::BuildResolvedCallExpr(Expr *Fn,
NamedDecl *NDecl,
}
// Bail out early if calling a builtin with custom type checking.
- if (BuiltinID && Context.BuiltinInfo.hasCustomTypechecking(BuiltinID))
- return CheckBuiltinFunctionCall(FDecl, BuiltinID, TheCall);
+ if (BuiltinID && Context.BuiltinInfo.hasCustomTypechecking(BuiltinID)) {
+ ExprResult E = CheckBuiltinFunctionCall(FDecl, BuiltinID, TheCall);
+ if (!E.isInvalid() && Context.BuiltinInfo.isImmediate(BuiltinID))
+ E = CheckForImmediateInvocation(E, FDecl);
+ return E;
+ }
if (getLangOpts().CUDA) {
if (Config) {
diff --git a/clang/test/Sema/builtin-redecl.cpp
b/clang/test/Sema/builtin-redecl.cpp
index 323c63e202883..31409a4d46a65 100644
--- a/clang/test/Sema/builtin-redecl.cpp
+++ b/clang/test/Sema/builtin-redecl.cpp
@@ -14,13 +14,18 @@ void __builtin_va_copy(double d);
// expected-error@+2 {{cannot redeclare builtin function '__builtin_va_end'}}
// expected-note@+1 {{'__builtin_va_end' is a builtin with type}}
void __builtin_va_end(__builtin_va_list);
-// RUN: %clang_cc1 %s -fsyntax-only -verify
-// RUN: %clang_cc1 %s -fsyntax-only -verify -x c
void __va_start(__builtin_va_list*, ...);
+ void *__builtin_assume_aligned(const void *, size_t, ...);
#ifdef __cplusplus
-void *__builtin_assume_aligned(const void *, size_t, ...) noexcept;
-#else
-void *__builtin_assume_aligned(const void *, size_t, ...);
+constexpr void *__builtin_assume_aligned(const void *, size_t, ...);
+ void *__builtin_assume_aligned(const void *, size_t, ...) noexcept;
+constexpr void *__builtin_assume_aligned(const void *, size_t, ...) noexcept;
+ void *__builtin_assume_aligned(const void *, size_t, ...) throw();
+constexpr void *__builtin_assume_aligned(const void *, size_t, ...) throw();
+
+// expected-error@+1 {{constexpr declaration of '__builtin_calloc' follows
non-constexpr declaration}}
+constexpr void *__builtin_calloc(size_t, size_t);
+// expected-note@-1 {{previous declaration is here}}
#endif
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