Add r134057 back, but splice the predecessor after the successors phi

nodes.

Original message:
Let simplify cfg simplify bb with only debug and lifetime intrinsics.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@134182 91177308-0d34-0410-b5e6-96231b3b80d8

test/Transforms/SimplifyCFG/lifetime.ll

@@ -0,0 +1,29 @@
+; RUN: opt < %s -simplifycfg -S | FileCheck %s
+
+; Test that a lifetime intrinsic doesn't prevent us from simplifying this.
+
+; CHECK: foo
+; CHECK: entry:
+; CHECK-NOT: bb0:
+; CHECK-NOT: bb1:
+; CHECK: ret
+define void @foo(i1 %x) {
+entry:
+  %a = alloca i8
+  call void @llvm.lifetime.start(i64 -1, i8* %a) nounwind
+  br i1 %x, label %bb0, label %bb1
+
+bb0:
+  call void @llvm.lifetime.end(i64 -1, i8* %a) nounwind
+  br label %bb1
+
+bb1:
+  call void @f()
+  ret void
+}
+
+declare void @f()
+
+declare void @llvm.lifetime.start(i64, i8* nocapture) nounwind
+
+declare void @llvm.lifetime.end(i64, i8* nocapture) nounwind