Generalize lsr code that optimize loop to count down towards zero.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@86715 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/test/Transforms/LoopStrengthReduce/count-to-zero.ll b/test/Transforms/LoopStrengthReduce/count-to-zero.ll
new file mode 100644
index 0000000..8cc3b5c
--- /dev/null
+++ b/test/Transforms/LoopStrengthReduce/count-to-zero.ll
@@ -0,0 +1,42 @@
+; RUN: opt < %s -loop-reduce -S | FileCheck %s
+; rdar://7382068
+
+define void @t(i32 %c) nounwind optsize {
+entry:
+ br label %bb6
+
+bb1: ; preds = %bb6
+ %tmp = icmp eq i32 %c_addr.1, 20 ; <i1> [#uses=1]
+ br i1 %tmp, label %bb2, label %bb3
+
+bb2: ; preds = %bb1
+ %tmp1 = tail call i32 @f20(i32 %c_addr.1) nounwind ; <i32> [#uses=1]
+ br label %bb7
+
+bb3: ; preds = %bb1
+ %tmp2 = icmp slt i32 %c_addr.1, 10 ; <i1> [#uses=1]
+ %tmp3 = add nsw i32 %c_addr.1, 1 ; <i32> [#uses=1]
+ %tmp4 = add i32 %c_addr.1, -1 ; <i32> [#uses=1]
+ %c_addr.1.be = select i1 %tmp2, i32 %tmp3, i32 %tmp4 ; <i32> [#uses=1]
+ %indvar.next = add i32 %indvar, 1 ; <i32> [#uses=1]
+; CHECK: sub i32 %lsr.iv, 1
+ br label %bb6
+
+bb6: ; preds = %bb3, %entry
+ %indvar = phi i32 [ %indvar.next, %bb3 ], [ 0, %entry ] ; <i32> [#uses=2]
+ %c_addr.1 = phi i32 [ %c_addr.1.be, %bb3 ], [ %c, %entry ] ; <i32> [#uses=7]
+ %tmp5 = icmp eq i32 %indvar, 9999 ; <i1> [#uses=1]
+; CHECK: icmp eq i32 %lsr.iv, 0
+ %tmp6 = icmp eq i32 %c_addr.1, 100 ; <i1> [#uses=1]
+ %or.cond = or i1 %tmp5, %tmp6 ; <i1> [#uses=1]
+ br i1 %or.cond, label %bb7, label %bb1
+
+bb7: ; preds = %bb6, %bb2
+ %c_addr.0 = phi i32 [ %tmp1, %bb2 ], [ %c_addr.1, %bb6 ] ; <i32> [#uses=1]
+ tail call void @bar(i32 %c_addr.0) nounwind
+ ret void
+}
+
+declare i32 @f20(i32)
+
+declare void @bar(i32)