[LoopUtils] Extend the scope of getLoopEstimatedTripCount

With this patch the getLoopEstimatedTripCount function will
accept also the loops where there are more than one exit but
all exits except latch block should ends up with a call to deopt.

This side exits should not impact the estimated trip count.

Reviewers: reames, mkuper, danielcdh
Reviewed By: reames
Subscribers: fhahn, lebedev.ri, hiraditya, llvm-commits
Differential Revision: https://reviews.llvm.org/D64553

llvm-svn: 366042

llvm/lib/Transforms/Utils/LoopUtils.cpp

@@ -621,20 +621,28 @@ void llvm::deleteDeadLoop(Loop *L, DominatorTree *DT = nullptr,
 }
 
 Optional<unsigned> llvm::getLoopEstimatedTripCount(Loop *L) {
-  // Only support loops with a unique exiting block, and a latch.
-  if (!L->getExitingBlock())
-    return None;
+  // Support loops with an exiting latch and other existing exists only
+  // deoptimize.
 
   // Get the branch weights for the loop's backedge.
-  BranchInst *LatchBR =
-      dyn_cast<BranchInst>(L->getLoopLatch()->getTerminator());
-  if (!LatchBR || LatchBR->getNumSuccessors() != 2)
+  BasicBlock *Latch = L->getLoopLatch();
+  if (!Latch)
+    return None;
+  BranchInst *LatchBR = dyn_cast<BranchInst>(Latch->getTerminator());
+  if (!LatchBR || LatchBR->getNumSuccessors() != 2 || !L->isLoopExiting(Latch))
     return None;
 
   assert((LatchBR->getSuccessor(0) == L->getHeader() ||
           LatchBR->getSuccessor(1) == L->getHeader()) &&
          "At least one edge out of the latch must go to the header");
 
+  SmallVector<BasicBlock *, 4> ExitBlocks;
+  L->getUniqueNonLatchExitBlocks(ExitBlocks);
+  if (any_of(ExitBlocks, [](const BasicBlock *EB) {
+        return !EB->getTerminatingDeoptimizeCall();
+      }))
+    return None;
+
   // To estimate the number of times the loop body was executed, we want to
   // know the number of times the backedge was taken, vs. the number of times
   // we exited the loop.