Add new RegionInfo pass.

The RegionInfo pass detects single entry single exit regions in a function,
where a region is defined as any subgraph that is connected to the remaining
graph at only two spots.
Furthermore an hierarchical region tree is built.
Use it by calling "opt -regions analyze" or "opt -view-regions".

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@109089 91177308-0d34-0410-b5e6-96231b3b80d8

test/Analysis/RegionInfo/loop_with_condition.ll

@@ -0,0 +1,46 @@
+; RUN: opt -regions -analyze < %s | FileCheck %s
+; RUN: opt -regions -stats < %s |& FileCheck -check-prefix=STAT %s
+
+; RUN: opt -regions -print-region-style=bb  -analyze < %s |& FileCheck -check-prefix=BBIT %s
+; RUN: opt -regions -print-region-style=rn  -analyze < %s |& FileCheck -check-prefix=RNIT %s
+
+define void @normal_condition() nounwind {
+0:
+        br label %"1"
+1:
+	br i1 1, label %"6", label %"2"
+2:
+	br i1 1, label %"3", label %"4"
+3:
+	br label %"5"
+4:
+	br label %"5"
+5:
+        br label %"8"
+8:
+        br i1 1, label %"7", label %"9"
+9:
+        br label %"2"
+7:
+        br label %"6"
+6:
+	ret void
+}
+
+; CHECK-NOT: =>
+; CHECK: [0] 0 => <Function Return>
+; CHECK-NEXT: [1] 1 => 6
+; CHECK-NEXT:   [2] 2 => 7
+; CHECK-NEXT:     [3] 2 => 5
+; STAT: 4 region - The # of regions
+; STAT: 1 region - The # of simple regions
+
+; BBIT: 0, 1, 6, 2, 3, 5, 8, 7, 9, 4,
+; BBIT: 1, 2, 3, 5, 8, 7, 9, 4,
+; BBIT: 2, 3, 5, 8, 9, 4,
+; BBIT: 2, 3, 4,
+
+; RNIT: 0, 1 => 6, 6,
+; RNIT: 1, 2 => 7, 7,
+; RNIT: 2 => 5, 5, 8, 9,
+; RNIT: 2, 3, 4,