New Test-Case for Region Analysis

While working on improvements to the region info analysis, this test case caused
an incorrect region 1 => 2 to be detected.  It is incorrect because entry has an
outgoing edge to 3.  This is interesting because 1 dom 2 and 2 pdom 1, which
should have been enough to prevent incoming forward edges into the region and
outgoing forward edges from the region.

Reviewers: grosser

Subscribers: llvm-commits

Contributed-by: Nandini Singhal <cs15mtech01004@iith.ac.in>

Differential Revision: https://reviews.llvm.org/D30603

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@296988 91177308-0d34-0410-b5e6-96231b3b80d8

test/Analysis/RegionInfo/outgoing_edge.ll

@@ -0,0 +1,33 @@
+; REQUIRES: asserts
+; RUN: opt -regions -analyze < %s | FileCheck %s
+; RUN: opt < %s -passes='print<regions>' 2>&1 | FileCheck %s
+
+; While working on improvements to the region info analysis, this test
+; case caused an incorrect region bb2 => bb3 to be detected. It is incorrect
+; because bb2 has an outgoing edge to bb4. This is interesting because
+; bb2 dom bb3 and bb3 pdom bb2, which should have been enough to prevent incoming
+; forward edges into the region and outgoing forward edges from the region.
+
+define void @meread_() nounwind {
+bb:
+   br label %bb1
+
+bb1:                                              ; preds = %bb4, %bb
+   br label %bb2
+
+bb2:                                              ; preds = %bb1
+  br i1 true, label %bb3, label %bb4
+
+bb3:                                              ; preds = %bb2
+  br i1 true, label %bb4, label %bb5
+
+bb4:                                              ; preds = %bb3, %bb2
+   br label %bb1
+
+bb5:                                              ; preds = %bb3
+   ret void
+ }
+
+; CHECK:      [0] bb => <Function Return>
+; CHECK-NEXT:   [1] bb1 => bb5
+; CHECK-NEXT: End region tree