AArch64: fix LowerCONCAT_VECTORS for new CodeGen.

The function was making too many assumptions about its input:

1. The NEON_VDUP optimisation was far too aggressive, assuming (I
think) that the input would always be BUILD_VECTOR.

2. We were treating most unknown concats as legal (by returning Op
rather than SDValue()). I think only concats of pairs of vectors are
actually legal.

http://llvm.org/PR19094

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@203450 91177308-0d34-0410-b5e6-96231b3b80d8

1 files changed, 21 insertions, 0 deletions

diff --git a/test/CodeGen/AArch64/concatvector-v8i8-bug.ll b/test/CodeGen/AArch64/concatvector-bugs.ll
index f8854c3b66..5889e22656 100644
--- a/test/CodeGen/AArch64/concatvector-v8i8-bug.ll
+++ b/test/CodeGen/AArch64/concatvector-bugs.ll
@@ -45,3 +45,24 @@ for.body130.us.us:                                ; preds = %for.body130.us.us,
   br label %for.body130.us.us
 }
 
+declare <1 x i16> @llvm.aarch64.neon.vuqrshrn.v1i16(<1 x i32>, i32)
+
+define <8 x i16> @test_splat(i32 %l) nounwind {
+; CHECK-LABEL: test_splat:
+; CHECK: ret
+  %lhs = insertelement <1 x i32> undef, i32 %l, i32 0
+  %shift = tail call <1 x i16> @llvm.aarch64.neon.vuqrshrn.v1i16(<1 x i32> %lhs, i32 11)
+  %vec = shufflevector <1 x i16> %shift, <1 x i16> undef, <8 x i32> zeroinitializer
+  ret <8 x i16> %vec
+}
+
+
+define <8 x i16> @test_notsplat(<8 x i16> %a, <8 x i16> %b, i32 %l) nounwind {
+; CHECK-LABEL: test_notsplat:
+; CHECK: ret
+entry:
+  %lhs = insertelement <1 x i32> undef, i32 %l, i32 0
+  %shift = tail call <1 x i16> @llvm.aarch64.neon.vuqrshrn.v1i16(<1 x i32> %lhs, i32 11)
+  %vec = shufflevector <1 x i16> %shift, <1 x i16> undef, <8 x i32> <i32 undef, i32 undef, i32 undef, i32 undef, i32 0, i32 0, i32 0, i32 0>
+  ret <8 x i16> %vec
+}