Imported Upstream version 6.10.0.49

Former-commit-id: 1d6753294b2993e1fbf92de9366bb9544db4189b

external/llvm-project/llvm/test/Transforms/TailCallElim/dup_tail.ll

@@ -0,0 +1,26 @@
+; REQUIRES: asserts
+; Duplicate the return into if.end to enable TCE.
+; RUN: opt -tailcallelim -stats -disable-output < %s 2>&1 | FileCheck %s
+
+; CHECK: 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
+}