Generalize lsr code that optimize loop to count down towards zero.

llvm-svn: 86715

1 files changed, 42 insertions, 0 deletions

diff --git a/llvm/test/Transforms/LoopStrengthReduce/count-to-zero.ll b/llvm/test/Transforms/LoopStrengthReduce/count-to-zero.ll
new file mode 100644
index 00000000000..8cc3b5c1034
--- /dev/null
+++ b/llvm/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)