Check sign to detect overflow before changing compare stride.

llvm-svn: 54710

1 files changed, 31 insertions, 0 deletions

diff --git a/llvm/test/Transforms/LoopStrengthReduce/2008-08-13-CmpStride.ll b/llvm/test/Transforms/LoopStrengthReduce/2008-08-13-CmpStride.ll
new file mode 100644
index 00000000000..fbd3c1e8a61
--- /dev/null
+++ b/llvm/test/Transforms/LoopStrengthReduce/2008-08-13-CmpStride.ll
@@ -0,0 +1,31 @@
+; RUN: llvm-as < %s | opt -loop-reduce | llvm-dis | grep add | count 2
+; PR 2662
+@g_3 = common global i16 0		; <i16*> [#uses=2]
+@"\01LC" = internal constant [4 x i8] c"%d\0A\00"		; <[4 x i8]*> [#uses=1]
+
+define void @func_1() nounwind {
+entry:
+	br label %bb
+
+bb:		; preds = %bb, %entry
+	%l_2.0.reg2mem.0 = phi i16 [ 0, %entry ], [ %t1, %bb ]		; <i16> [#uses=2]
+	%t0 = shl i16 %l_2.0.reg2mem.0, 1		; <i16>:0 [#uses=1]
+	volatile store i16 %t0, i16* @g_3, align 2
+	%t1 = add i16 %l_2.0.reg2mem.0, -3		; <i16>:1 [#uses=2]
+	%t2 = icmp slt i16 %t1, 1		; <i1>:2 [#uses=1]
+	br i1 %t2, label %bb, label %return
+
+return:		; preds = %bb
+	ret void
+}
+
+define i32 @main() nounwind {
+entry:
+	tail call void @func_1( ) nounwind
+	volatile load i16* @g_3, align 2		; <i16>:0 [#uses=1]
+	zext i16 %0 to i32		; <i32>:1 [#uses=1]
+	tail call i32 (i8*, ...)* @printf( i8* getelementptr ([4 x i8]* @"\01LC", i32 0, i32 0), i32 %1 ) nounwind		; <i32>:2 [#uses=0]
+	ret i32 0
+}
+
+declare i32 @printf(i8*, ...) nounwind