[llvm] [IndVarSimplify] Fix `IndVarSimplify` to skip on unfolding predicates when the loop contains control convergence operations. (PR #165643)

[Nikita Popov via llvm-commits]

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@@ -1859,6 +1859,37 @@ bool IndVarSimplify::predicateLoopExits(Loop *L, SCEVExpander &Rewriter) {
         }
       }
 
+  // If the loop body uses a convergence token defined within the loop, skip
+  // predication. This is to avoid changing the convergence behavior of the
+  // loop.
+  SmallVector<BasicBlock *, 16> blocks = ExitingBlocks;
+  SmallVector<Value *, 16> tokens = {};
+  size_t index = 0; // Assume Exiting Blocks are sorted.
+  while (index < blocks.size()) {
+    BasicBlock *BB = blocks[index];
+    index++;
+    const auto exitingBlockName = BB->getName();
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nikic wrote:

Unused variable.

https://github.com/llvm/llvm-project/pull/165643