[clang] [Clang][CodeGen] Bail out on constexpr unknown values in ConstantEmitter (PR #127525)

[via cfe-commits]

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@@ -1883,8 +1883,10 @@ llvm::Constant *ConstantEmitter::tryEmitPrivateForVarInit(const VarDecl &D) {
 
   // Try to emit the initializer.  Note that this can allow some things that
   // are not allowed by tryEmitPrivateForMemory alone.
-  if (APValue *value = D.evaluateValue())
-    return tryEmitPrivateForMemory(*value, destType);
+  if (APValue *value = D.evaluateValue()) {
+    if (!value->allowConstexprUnknown())
+      return tryEmitPrivateForMemory(*value, destType);
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cor3ntin wrote:

I think a comment here would be useful

https://github.com/llvm/llvm-project/pull/127525