[PATCH] D110924: [LoopUtils] Consider unreachable-terminated blocks as deoptimizing

[Dmitry Makogon via Phabricator via llvm-commits]

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Previously in function `getExpectedExitLoopLatchBranch` we considered a block deoptimizing if it had a terminating deoptimize call. 
Now updated to it to keep in sync with almost the same logic in LoopPeel (see https://reviews.llvm.org/D110922).
>From that patch:

> Added support for peeling loops with "deoptimizing" exits - such exits that it or any of its children (or any of their children, etc) either has a @llvm.experimental.deoptimize call
> prior to the terminating return instruction of this basic block or is terminated with unreachable. All blocks in the the sequence must have a single successor, maybe except for the > last one.
> Previously we only checked the exit block for being deoptimizing. Now we check if the last reachable block from the exit is deoptimizing.

So now we can consider a block deoptimizing if it meets the condition from the quote.


Repository:
  rG LLVM Github Monorepo

https://reviews.llvm.org/D110924

Files:
  llvm/lib/Transforms/Utils/LoopUtils.cpp


Index: llvm/lib/Transforms/Utils/LoopUtils.cpp
===================================================================
--- llvm/lib/Transforms/Utils/LoopUtils.cpp
+++ llvm/lib/Transforms/Utils/LoopUtils.cpp
@@ -778,8 +778,9 @@
 
 
 /// Checks if \p L has single exit through latch block except possibly
-/// "deoptimizing" exits. Returns branch instruction terminating the loop
-/// latch if above check is successful, nullptr otherwise.
+/// "deoptimizing" (@llvm.experimental.deoptimize or unreachable-terminated)
+/// exits. Returns branch instruction terminating the loop latch if above check
+/// is successful, nullptr otherwise.
 static BranchInst *getExpectedExitLoopLatchBranch(Loop *L) {
   BasicBlock *Latch = L->getLoopLatch();
   if (!Latch)
@@ -795,8 +796,9 @@
 
   SmallVector<BasicBlock *, 4> ExitBlocks;
   L->getUniqueNonLatchExitBlocks(ExitBlocks);
-  if (any_of(ExitBlocks, [](const BasicBlock *EB) {
-        return !EB->getTerminatingDeoptimizeCall();
+  SmallVector<const BasicBlock *, 8> DeoptimizingBlocks;
+  if (any_of(ExitBlocks, [&](const BasicBlock *EB) {
+        return !IsBlockDeoptimizing(EB, DeoptimizingBlocks);
       }))
     return nullptr;
 


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