[clang] [Clang] Instantiate constexpr function when they are needed. (PR #173537)

[Corentin Jabot via cfe-commits]

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@@ -20707,6 +20739,8 @@ bool Expr::EvaluateAsInitializer(APValue &Value, const ASTContext &Ctx,
                     : EvaluationMode::ConstantFold);
   Info.setEvaluatingDecl(VD, Value);
   Info.InConstantContext = IsConstantInitialization;
+  Info.TryConstantInitialization =
+      !VD->isConstexpr() && !VD->hasAttr<ConstInitAttr>();
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cor3ntin wrote:

It's the other way around - when trying to initialize a constant-initialized  non-constexpr variable we do **not** want to force an instantiation (it may not yet be available or a more specialized definition may be provided later)

https://github.com/llvm/llvm-project/pull/173537