+; RUN: opt -jump-threading -S %s | FileCheck %s
+
+; Check that we thread arg2neg -> checkpos -> end.
+;
+; LazyValueInfo would previously fail to analyze the value of %arg in arg2neg
+; because its predecessing blocks (checkneg) hadn't been processed yet (PR21238)
+
+; CHECK-LABEL: @test_jump_threading
+; CHECK: arg2neg:
+; CHECK-NEXT: br i1 %arg1, label %end, label %checkpos.thread
+; CHECK: checkpos.thread:
+; CHECK-NEXT: br label %end
+
+define i32 @test_jump_threading(i1 %arg1, i32 %arg2) {
+checkneg:
+ %cmp = icmp slt i32 %arg2, 0
+ br i1 %cmp, label %arg2neg, label %checkpos
+
+arg2neg:
+ br i1 %arg1, label %end, label %checkpos
+
+checkpos:
+ %cmp2 = icmp sgt i32 %arg2, 0
+ br i1 %cmp2, label %arg2pos, label %end
+
+arg2pos:
+ br label %end
+
+end:
+ %0 = phi i32 [ 1, %arg2neg ], [ 2, %checkpos ], [ 3, %arg2pos ]
+ ret i32 %0
+}
+
+
+; arg2neg has an edge back to itself. If LazyValueInfo is not careful when
+; visiting predecessors, it could get into an infinite loop.
+
+; CHECK-LABEL: test_infinite_loop
+
+define i32 @test_infinite_loop(i1 %arg1, i32 %arg2) {
+checkneg:
+ %cmp = icmp slt i32 %arg2, 0
+ br i1 %cmp, label %arg2neg, label %checkpos
+
+arg2neg:
+ br i1 %arg1, label %arg2neg, label %checkpos
+
+checkpos:
+ %cmp2 = icmp sgt i32 %arg2, 0
+ br i1 %cmp2, label %arg2pos, label %end
+
+arg2pos:
+ br label %end
+
+end:
+ %0 = phi i32 [ 2, %checkpos ], [ 3, %arg2pos ]
+ ret i32 %0
+}