Add looping testcase that broke in r272987

llvm-svn: 273081

llvm/test/Transforms/InstCombine/trunc.ll

@@ -160,3 +160,24 @@ define i32 @trunc_bitcast3(<4 x i32> %v) {
 ; CHECK-NEXT:  ret i32 %ext
 }
 
+; CHECK-LABEL: @trunc_shl_infloop(
+; CHECK: %tmp = lshr i64 %arg, 1
+; CHECK: %tmp21 = shl i64 %tmp, 2
+; CHECK: %tmp2 = trunc i64 %tmp21 to i32
+; CHECK: icmp sgt i32 %tmp2, 0
+define void @trunc_shl_infloop(i64 %arg) {
+bb:
+  %tmp = lshr i64 %arg, 1
+  %tmp1 = trunc i64 %tmp to i32
+  %tmp2 = shl i32 %tmp1, 2
+  %tmp3 = icmp sgt i32 %tmp2, 0
+  br i1 %tmp3, label %bb2, label %bb1
+
+bb1:
+  %tmp5 = sub i32 0, %tmp1
+  %tmp6 = sub i32 %tmp5, 1
+  unreachable
+
+bb2:
+  unreachable
+}