[clang] [clang] Allow 'convergent' to be a statement attribute (PR #100637)

[Eli Friedman via cfe-commits]

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@@ -0,0 +1,99 @@
+// RUN: %clang_cc1 -emit-llvm %s -triple x86_64-unknown-linux-gnu -o - | FileCheck %s
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efriedma-quic wrote:

Consider using update_cc_test_checks.py.

I'd like to see checks that we emit convergence tokens on targets where that's the default.

https://github.com/llvm/llvm-project/pull/100637