[llvm] [GlobalISel] convergence control tokens and intrinsics (PR #67006)

[Matt Arsenault via llvm-commits]

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@@ -45,6 +45,14 @@ class LLT {
                /*AddressSpace=*/0};
   }
 
+  /// Get a low-level token; just a scalar with zero bits (or no size).
+  static constexpr LLT token() {
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arsenm wrote:

This should get some new tests in unittests/CodeGen/LowLevelTypeTest.cpp

https://github.com/llvm/llvm-project/pull/67006