Fix Value::stripPointerCasts and BasicAA to avoid trouble on

code in unreachable blocks, which have have use-def cycles.
This fixes PR7514.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@107071 91177308-0d34-0410-b5e6-96231b3b80d8

test/Analysis/BasicAA/unreachable-block.ll

@@ -0,0 +1,16 @@
+; RUN: opt -aa-eval -disable-output < %s >& /dev/null
+
+; BasicAA shouldn't infinitely recurse on the use-def cycles in
+; unreachable code.
+
+define void @func_2() nounwind {
+entry:
+  unreachable
+
+bb:
+  %t = select i1 undef, i32* %t, i32* undef
+  %p = select i1 undef, i32* %p, i32* %p
+  %q = select i1 undef, i32* undef, i32* %p
+  %a = getelementptr i8* %a, i32 0
+  unreachable
+}