[ARM] Do not use vtrn for vectorshuffle if the order is reversed

The tests in isVTRNMask and isVTRN_v_undef_Mask should also check that the elements of the upper and lower half of the vectorshuffle occur in the correct order when both halves are used. Without this test the code assumes that it is correct to use vector transpose (vtrn) for the masks <1, 1, 0, 0> and <1, 3, 0, 2>, among others, but the transpose actually incorrectly generates shuffles for <0, 0, 1, 1> and <0, 2, 1, 3> in this case.

Patch by Jeroen Ketema!

llvm-svn: 247254

1 files changed, 10 insertions, 0 deletions

diff --git a/llvm/test/CodeGen/ARM/vzip.ll b/llvm/test/CodeGen/ARM/vzip.ll
index e7b7da333f4..24386a236f4 100644
--- a/llvm/test/CodeGen/ARM/vzip.ll
+++ b/llvm/test/CodeGen/ARM/vzip.ll
@@ -295,3 +295,13 @@ entry:
   ret <4 x i32> %0
 }
 
+define void @vzip_undef_rev_shufflemask_vtrn(<2 x i32>* %A, <4 x i32>* %B) {
+entry:
+  ; CHECK-LABEL: vzip_undef_rev_shufflemask_vtrn
+  ; CHECK-NOT: vtrn
+  ; CHECK: vzip
+  %tmp1 = load <2 x i32>, <2 x i32>* %A
+  %0 = shufflevector <2 x i32> %tmp1, <2 x i32> undef, <4 x i32> <i32 1, i32 1, i32 0, i32 0>
+  store <4 x i32> %0, <4 x i32>* %B
+  ret void
+}