[clang] [clang][bytecode] Ignore function calls with depth > 0... (PR #129887)

[Timm Baeder via cfe-commits]

https://github.com/tbaederr created https://github.com/llvm/llvm-project/pull/129887

... when checking for a potential constant expression. This is also what the current interpreter does.

>From 8e4267678319e98b2119233e13b5e73869bc3a21 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Timm=20B=C3=A4der?= <tbaeder at redhat.com>
Date: Wed, 5 Mar 2025 15:17:30 +0100
Subject: [PATCH] [clang][bytecode] Ignore function calls with depth > 0...

... when checking for a potential constant expression. This is also
what the current interpreter does.
---
 clang/lib/AST/ByteCode/Interp.cpp     |  3 +++
 clang/test/AST/ByteCode/functions.cpp | 13 +++++++++++++
 2 files changed, 16 insertions(+)

diff --git a/clang/lib/AST/ByteCode/Interp.cpp b/clang/lib/AST/ByteCode/Interp.cpp
index a2090f3e85e08..1107c0c32792f 100644
--- a/clang/lib/AST/ByteCode/Interp.cpp
+++ b/clang/lib/AST/ByteCode/Interp.cpp
@@ -714,6 +714,9 @@ bool CheckCallable(InterpState &S, CodePtr OpPC, const Function *F) {
     return false;
   }
 
+  if (S.checkingPotentialConstantExpression() && S.Current->getDepth() != 0)
+    return false;
+
   if (F->isConstexpr() && F->hasBody() &&
       (F->getDecl()->isConstexpr() || F->getDecl()->hasAttr<MSConstexprAttr>()))
     return true;
diff --git a/clang/test/AST/ByteCode/functions.cpp b/clang/test/AST/ByteCode/functions.cpp
index a7c8836eac6b8..a767d104b3c8a 100644
--- a/clang/test/AST/ByteCode/functions.cpp
+++ b/clang/test/AST/ByteCode/functions.cpp
@@ -681,3 +681,16 @@ namespace StableAddress {
   static_assert(sum<str{"$hello $world."}>() == 1234, "");
 }
 #endif
+
+namespace NoDiags {
+  void huh();
+  template <unsigned>
+  constexpr void hd_fun() {
+    huh();
+  }
+
+  constexpr bool foo() {
+    hd_fun<1>();
+    return true;
+  }
+}