Add a test for TCE return duplication.

llvm-svn: 124527

2 files changed, 25 insertions, 0 deletions

diff --git a/llvm/lib/Transforms/Scalar/TailRecursionElimination.cpp b/llvm/lib/Transforms/Scalar/TailRecursionElimination.cpp
index 61f230804f5..50d4cc33171 100644
--- a/llvm/lib/Transforms/Scalar/TailRecursionElimination.cpp
+++ b/llvm/lib/Transforms/Scalar/TailRecursionElimination.cpp
@@ -72,6 +72,7 @@
 using namespace llvm;
 
 STATISTIC(NumEliminated, "Number of tail calls removed");
+STATISTIC(NumRetDuped,   "Number of return duplicated");
 STATISTIC(NumAccumAdded, "Number of accumulators introduced");
 
 namespace {
@@ -606,6 +607,7 @@ bool TailCallElim::FoldReturnAndProcessPred(BasicBlock *BB,
       EliminateRecursiveTailCall(CI, FoldReturnIntoUncondBranch(Ret, BB, Pred),
                                  OldEntry, TailCallsAreMarkedTail, ArgumentPHIs,
                                  CannotTailCallElimCallsMarkedTail);
+      ++NumRetDuped;
       Change = true;
     }
   }
diff --git a/llvm/test/Transforms/TailCallElim/dup_tail.ll b/llvm/test/Transforms/TailCallElim/dup_tail.ll
new file mode 100644
index 00000000000..93638804f92
--- /dev/null
+++ b/llvm/test/Transforms/TailCallElim/dup_tail.ll
@@ -0,0 +1,23 @@
+; Duplicate the return into if.end to enable TCE.
+; RUN: opt %s -tailcallelim -stats -disable-output |& grep {Number of return duplicated}
+
+define i32 @fib(i32 %n) nounwind ssp {
+entry:
+  %cmp = icmp slt i32 %n, 2
+  br i1 %cmp, label %if.then, label %if.end
+
+if.then:                                          ; preds = %entry
+  br label %return
+
+if.end:                                           ; preds = %entry
+  %sub = add nsw i32 %n, -2
+  %call = call i32 @fib(i32 %sub)
+  %sub3 = add nsw i32 %n, -1
+  %call4 = call i32 @fib(i32 %sub3)
+  %add = add nsw i32 %call, %call4
+  br label %return
+
+return:                                           ; preds = %if.end, %if.then
+  %retval.0 = phi i32 [ 1, %if.then ], [ %add, %if.end ]
+  ret i32 %retval.0
+}