1 files changed, 49 insertions, 0 deletions
diff --git a/llvm/test/Transforms/LoopVectorize/store-shuffle-bug.ll b/llvm/test/Transforms/LoopVectorize/store-shuffle-bug.ll
new file mode 100644
index 00000000000..62b148e2c79
--- /dev/null
+++ b/llvm/test/Transforms/LoopVectorize/store-shuffle-bug.ll
@@ -0,0 +1,49 @@
+; RUN: opt -S -basicaa -loop-vectorize -force-vector-interleave=1 -force-vector-width=4 -dce -instcombine < %s | FileCheck %s
+
+target datalayout = "e-p:64:64:64-i1:8:8-i8:8:8-i16:16:16-i32:32:32-i64:64:64-f32:32:32-f64:64:64-v64:64:64-v128:128:128-a0:0:64-s0:64:64-f80:128:128-n8:16:32:64-S128"
+
+@uf = common global [100 x i32] zeroinitializer, align 16
+@xi = common global [100 x i32] zeroinitializer, align 16
+@q = common global [100 x i32] zeroinitializer, align 16
+
+; PR16455
+
+
+; Due to a bug in the way we handled reverse induction stores we would generate
+; a shuffle too many.
+
+define void @t()  {
+entry:
+  br label %for.body
+
+; CHECK-LABEL: @t(
+; CHECK: vector.body:
+; CHECK: [[VAR1:%[a-zA-Z0-9.]+]] = load <4 x i32>
+; CHECK: [[VAR2:%[a-zA-Z0-9.]+]] = load <4 x i32>
+; CHECK: [[VAR3:%[a-zA-Z0-9]+]] = add nsw <4 x i32> [[VAR2]], [[VAR1]]
+; CHECK: store <4 x i32> [[VAR3]]
+; CHECK: [[VAR4:%[a-zA-Z0-9.]+]] = load <4 x i32>
+; CHECK: add nsw <4 x i32> [[VAR3]], [[VAR4]]
+; CHECK-NOT: shufflevector
+
+for.body:
+  %indvars.iv = phi i64 [ 93, %entry ], [ %indvars.iv.next, %for.body ]
+  %0 = add i64 %indvars.iv, 1
+  %arrayidx = getelementptr inbounds [100 x i32], [100 x i32]* @uf, i64 0, i64 %0
+  %arrayidx3 = getelementptr inbounds [100 x i32], [100 x i32]* @xi, i64 0, i64 %0
+  %1 = load i32, i32* %arrayidx3, align 4
+  %2 = load i32, i32* %arrayidx, align 4
+  %add4 = add nsw i32 %2, %1
+  store i32 %add4, i32* %arrayidx, align 4
+  %arrayidx7 = getelementptr inbounds [100 x i32], [100 x i32]* @q, i64 0, i64 %0
+  %3 = load i32, i32* %arrayidx7, align 4
+  %add8 = add nsw i32 %add4, %3
+  store i32 %add8, i32* %arrayidx, align 4
+  %indvars.iv.next = add i64 %indvars.iv, -1
+  %4 = trunc i64 %indvars.iv.next to i32
+  %cmp = icmp ugt i32 %4, 2
+  br i1 %cmp, label %for.body, label %for.end
+
+for.end:
+  ret void
+}