[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

3 files changed, 50 insertions, 0 deletions

diff --git a/llvm/test/CodeGen/ARM/vtrn.ll b/llvm/test/CodeGen/ARM/vtrn.ll
index 5c22d1a44f6..89af2318bfb 100644
--- a/llvm/test/CodeGen/ARM/vtrn.ll
+++ b/llvm/test/CodeGen/ARM/vtrn.ll
@@ -371,3 +371,31 @@ define <8 x i8> @vtrn_mismatched_builvector1(<8 x i8> %tr0, <8 x i8> %tr1,
   %rv = select <8 x i1> %c, <8 x i8> %tr0, <8 x i8> %tr1
   ret <8 x i8> %rv
 }
+
+; Negative test that should not generate a vtrn
+define void @lower_twice_no_vtrn(<4 x i16>* %A, <4 x i16>* %B, <8 x i16>* %C) {
+entry:
+  ; CHECK-LABEL: lower_twice_no_vtrn
+  ; CHECK: @ BB#0:
+  ; CHECK-NOT: vtrn
+  ; CHECK: mov pc, lr
+  %tmp1 = load <4 x i16>, <4 x i16>* %A
+  %tmp2 = load <4 x i16>, <4 x i16>* %B
+  %0 = shufflevector <4 x i16> %tmp1, <4 x i16> %tmp2, <8 x i32> <i32 undef, i32 5, i32 3, i32 7, i32 1, i32 5, i32 3, i32 7>
+  store <8 x i16> %0, <8 x i16>* %C
+  ret void
+}
+
+; Negative test that should not generate a vtrn
+define void @upper_twice_no_vtrn(<4 x i16>* %A, <4 x i16>* %B, <8 x i16>* %C) {
+entry:
+  ; CHECK-LABEL: upper_twice_no_vtrn
+  ; CHECK: @ BB#0:
+  ; CHECK-NOT: vtrn
+  ; CHECK: mov pc, lr
+  %tmp1 = load <4 x i16>, <4 x i16>* %A
+  %tmp2 = load <4 x i16>, <4 x i16>* %B
+  %0 = shufflevector <4 x i16> %tmp1, <4 x i16> %tmp2, <8 x i32> <i32 0, i32 undef, i32 2, i32 6, i32 0, i32 4, i32 2, i32 6>
+  store <8 x i16> %0, <8 x i16>* %C
+  ret void
+}
diff --git a/llvm/test/CodeGen/ARM/vuzp.ll b/llvm/test/CodeGen/ARM/vuzp.ll
index 570623e4f64..6c24348b8cf 100644
--- a/llvm/test/CodeGen/ARM/vuzp.ll
+++ b/llvm/test/CodeGen/ARM/vuzp.ll
@@ -286,6 +286,18 @@ entry:
   ret <4 x i32> %0
 }
 
+define void @vuzp_rev_shufflemask_vtrn(<2 x i32>* %A, <2 x i32>* %B, <4 x i32>* %C) {
+entry:
+  ; CHECK-LABEL: vuzp_rev_shufflemask_vtrn
+  ; CHECK-NOT: vtrn
+  ; CHECK: vuzp
+  %tmp1 = load <2 x i32>, <2 x i32>* %A
+  %tmp2 = load <2 x i32>, <2 x i32>* %B
+  %0 = shufflevector <2 x i32> %tmp1, <2 x i32> %tmp2, <4 x i32> <i32 1, i32 3, i32 0, i32 2>
+  store <4 x i32> %0, <4 x i32>* %C
+  ret void
+}
+
 define <8 x i8> @vuzp_trunc(<8 x i8> %in0, <8 x i8> %in1, <8 x i32> %cmp0, <8 x i32> %cmp1) {
 ; In order to create the select we need to truncate the vcgt result from a vector of i32 to a vector of i8.
 ; This results in a build_vector with mismatched types. We will generate two vmovn.i32 instructions to
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
+}