[llvm] [RFC] implement convergence control in MIR using SelectionDAG (PR #71785)

[Matt Arsenault via llvm-commits]

================
@@ -8351,7 +8382,8 @@ void SelectionDAGBuilder::LowerCallTo(const CallBase &CB, SDValue Callee,
       .setConvergent(CB.isConvergent())
       .setIsPreallocated(
           CB.countOperandBundlesOfType(LLVMContext::OB_preallocated) != 0)
-      .setCFIType(CFIType);
+      .setCFIType(CFIType)
+      .setConvergenceControlToken(ConvControlToken);
----------------
arsenm wrote:

Skip creating the undef if it's not a convergent call?

https://github.com/llvm/llvm-project/pull/71785