[clang] [clang][bytecode] Save Constexpr bit in Function (PR #142793)

[Timm Baeder via cfe-commits]

https://github.com/tbaederr created 
https://github.com/llvm/llvm-project/pull/142793

Rename isConstexpr to isValid, the former was always a bad name. Save a 
constexpr bit in Function so we don't have to access the decl in CheckCallable.

>From f5dbb8228c19e5dd95bd4da65fe4c6f394df32c2 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Timm=20B=C3=A4der?= <tbae...@redhat.com>
Date: Wed, 4 Jun 2025 14:32:39 +0200
Subject: [PATCH] [clang][bytecode] Save Constexpr bit in Function

Rename isConstexpr to isValid, the former was always a bad name.
Save a constexpr bit in Function so we don't have to access the decl in
CheckCallable.
---
 clang/lib/AST/ByteCode/Context.cpp  |  2 +-
 clang/lib/AST/ByteCode/Function.cpp |  2 ++
 clang/lib/AST/ByteCode/Function.h   |  7 +++++--
 clang/lib/AST/ByteCode/Interp.cpp   | 18 +++++++++---------
 4 files changed, 17 insertions(+), 12 deletions(-)

diff --git a/clang/lib/AST/ByteCode/Context.cpp 
b/clang/lib/AST/ByteCode/Context.cpp
index d73705b6126fe..971eb7fd58876 100644
--- a/clang/lib/AST/ByteCode/Context.cpp
+++ b/clang/lib/AST/ByteCode/Context.cpp
@@ -49,7 +49,7 @@ bool Context::isPotentialConstantExpr(State &Parent, const 
FunctionDecl *FD) {
   if (!Run(Parent, Func))
     return false;
 
-  return Func->isConstexpr();
+  return Func->isValid();
 }
 
 bool Context::evaluateAsRValue(State &Parent, const Expr *E, APValue &Result) {
diff --git a/clang/lib/AST/ByteCode/Function.cpp 
b/clang/lib/AST/ByteCode/Function.cpp
index e421dad062817..9eb6744ea47ad 100644
--- a/clang/lib/AST/ByteCode/Function.cpp
+++ b/clang/lib/AST/ByteCode/Function.cpp
@@ -27,6 +27,7 @@ Function::Function(Program &P, FunctionDeclTy Source, 
unsigned ArgSize,
   if (const auto *F = dyn_cast<const FunctionDecl *>(Source)) {
     Variadic = F->isVariadic();
     Immediate = F->isImmediateFunction();
+    Constexpr = F->isConstexpr() || F->hasAttr<MSConstexprAttr>();
     if (const auto *CD = dyn_cast<CXXConstructorDecl>(F)) {
       Virtual = CD->isVirtual();
       Kind = FunctionKind::Ctor;
@@ -48,6 +49,7 @@ Function::Function(Program &P, FunctionDeclTy Source, 
unsigned ArgSize,
     Variadic = false;
     Virtual = false;
     Immediate = false;
+    Constexpr = false;
   }
 }
 
diff --git a/clang/lib/AST/ByteCode/Function.h 
b/clang/lib/AST/ByteCode/Function.h
index 8b577858474af..de88f3ded34dc 100644
--- a/clang/lib/AST/ByteCode/Function.h
+++ b/clang/lib/AST/ByteCode/Function.h
@@ -150,12 +150,13 @@ class Function final {
   /// Returns the source information at a given PC.
   SourceInfo getSource(CodePtr PC) const;
 
-  /// Checks if the function is valid to call in constexpr.
-  bool isConstexpr() const { return IsValid || isLambdaStaticInvoker(); }
+  /// Checks if the function is valid to call.
+  bool isValid() const { return IsValid || isLambdaStaticInvoker(); }
 
   /// Checks if the function is virtual.
   bool isVirtual() const { return Virtual; };
   bool isImmediate() const { return Immediate; }
+  bool isConstexpr() const { return Constexpr; }
 
   /// Checks if the function is a constructor.
   bool isConstructor() const { return Kind == FunctionKind::Ctor; }
@@ -303,6 +304,8 @@ class Function final {
   unsigned Virtual : 1;
   LLVM_PREFERRED_TYPE(bool)
   unsigned Immediate : 1;
+  LLVM_PREFERRED_TYPE(bool)
+  unsigned Constexpr : 1;
 
 public:
   /// Dumps the disassembled bytecode to \c llvm::errs().
diff --git a/clang/lib/AST/ByteCode/Interp.cpp 
b/clang/lib/AST/ByteCode/Interp.cpp
index db91e5e328485..5c8abffb3a99d 100644
--- a/clang/lib/AST/ByteCode/Interp.cpp
+++ b/clang/lib/AST/ByteCode/Interp.cpp
@@ -857,23 +857,22 @@ bool CheckCallable(InterpState &S, CodePtr OpPC, const 
Function *F) {
     return false;
   }
 
-  // Bail out if the function declaration itself is invalid.  We will
-  // have produced a relevant diagnostic while parsing it, so just
-  // note the problematic sub-expression.
-  if (F->getDecl()->isInvalidDecl())
-    return Invalid(S, OpPC);
-
   if (S.checkingPotentialConstantExpression() && S.Current->getDepth() != 0)
     return false;
 
-  if (F->isConstexpr() && F->hasBody() &&
-      (F->getDecl()->isConstexpr() || 
F->getDecl()->hasAttr<MSConstexprAttr>()))
+  if (F->isValid() && F->hasBody() && F->isConstexpr())
     return true;
 
   // Implicitly constexpr.
   if (F->isLambdaStaticInvoker())
     return true;
 
+  // Bail out if the function declaration itself is invalid.  We will
+  // have produced a relevant diagnostic while parsing it, so just
+  // note the problematic sub-expression.
+  if (F->getDecl()->isInvalidDecl())
+    return Invalid(S, OpPC);
+
   // Diagnose failed assertions specially.
   if (S.Current->getLocation(OpPC).isMacroID() &&
       F->getDecl()->getIdentifier()) {
@@ -923,7 +922,8 @@ bool CheckCallable(InterpState &S, CodePtr OpPC, const 
Function *F) {
       // for a constant expression. It might be defined at the point we're
       // actually calling it.
       bool IsExtern = DiagDecl->getStorageClass() == SC_Extern;
-      if (!DiagDecl->isDefined() && !IsExtern && DiagDecl->isConstexpr() &&
+      bool IsDefined = F->isDefined();
+      if (!IsDefined && !IsExtern && DiagDecl->isConstexpr() &&
           S.checkingPotentialConstantExpression())
         return false;
 

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