https://github.com/MitalAshok updated
https://github.com/llvm/llvm-project/pull/91894
>From 56aed689dc5825fc5bacc6dfdff58ee0eaf71f82 Mon Sep 17 00:00:00 2001
From: Mital Ashok
Date: Sun, 12 May 2024 19:48:24 +0100
Subject: [PATCH 1/4] [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 (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 : 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(New->getConstexprKind())
-<< static_cast(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(New->getConstexprKind())
+ << static_cast(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
