Handle ands with 0 and shifts by 0 correctly. These aren't

common, but indvars shouldn't crash on them. This fixes PR4054.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@70051 91177308-0d34-0410-b5e6-96231b3b80d8

test/Transforms/IndVarSimplify/avoid-i0.ll

@@ -0,0 +1,23 @@
+; RUN: llvm-as < %s | opt -indvars
+; PR4054
+
+; Don't treat an and with 0 as a mask (trunc+zext).
+
+define i32 @int80(i8 signext %p_71) nounwind {
+entry:
+	br label %bb
+
+bb:		; preds = %bb6, %entry
+	%p_71_addr.0 = phi i8 [ %p_71, %entry ], [ %0, %bb6 ]		; <i8> [#uses=0]
+	br i1 false, label %bb4, label %bb1
+
+bb1:		; preds = %bb
+	ret i32 0
+
+bb4:		; preds = %bb4, %bb
+	br i1 false, label %bb6, label %bb4
+
+bb6:		; preds = %bb4
+	%0 = and i8 0, 0		; <i8> [#uses=1]
+	br label %bb
+}