From daff1869974b401901a63039e66e4f17b6ea35c1 Mon Sep 17 00:00:00 2001
From: Martin Storsjo <martin@martin.st>
Date: Sat, 19 Aug 2017 19:47:48 +0000
Subject: [PATCH] [ARM] Check the right order for halves of VZIP/VUZP if both
 parts are used

This is the exact same fix as in SVN r247254. In that commit, the fix was
applied only for isVTRNMask and isVTRN_v_undef_Mask, but the same issue
is present for VZIP/VUZP as well.

This fixes PR33921.

Differential Revision: https://reviews.llvm.org/D36899

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@311258 91177308-0d34-0410-b5e6-96231b3b80d8
---
 lib/Target/ARM/ARMISelLowering.cpp | 20 ++++++++++++++++----
 test/CodeGen/ARM/vzip.ll           | 19 +++++++++++++++++++
 2 files changed, 35 insertions(+), 4 deletions(-)

diff --git a/lib/Target/ARM/ARMISelLowering.cpp b/lib/Target/ARM/ARMISelLowering.cpp
index ff8491d2e62..320d7ccfbc2 100644
--- a/lib/Target/ARM/ARMISelLowering.cpp
+++ b/lib/Target/ARM/ARMISelLowering.cpp
@@ -5901,7 +5901,10 @@ static bool isVUZPMask(ArrayRef<int> M, EVT VT, unsigned &WhichResult) {
     return false;
 
   for (unsigned i = 0; i < M.size(); i += NumElts) {
-    WhichResult = M[i] == 0 ? 0 : 1;
+    if (M.size() == NumElts * 2)
+      WhichResult = i / NumElts;
+    else
+      WhichResult = M[i] == 0 ? 0 : 1;
     for (unsigned j = 0; j < NumElts; ++j) {
       if (M[i+j] >= 0 && (unsigned) M[i+j] != 2 * j + WhichResult)
         return false;
@@ -5932,7 +5935,10 @@ static bool isVUZP_v_undef_Mask(ArrayRef<int> M, EVT VT, unsigned &WhichResult){
 
   unsigned Half = NumElts / 2;
   for (unsigned i = 0; i < M.size(); i += NumElts) {
-    WhichResult = M[i] == 0 ? 0 : 1;
+    if (M.size() == NumElts * 2)
+      WhichResult = i / NumElts;
+    else
+      WhichResult = M[i] == 0 ? 0 : 1;
     for (unsigned j = 0; j < NumElts; j += Half) {
       unsigned Idx = WhichResult;
       for (unsigned k = 0; k < Half; ++k) {
@@ -5972,7 +5978,10 @@ static bool isVZIPMask(ArrayRef<int> M, EVT VT, unsigned &WhichResult) {
     return false;
 
   for (unsigned i = 0; i < M.size(); i += NumElts) {
-    WhichResult = M[i] == 0 ? 0 : 1;
+    if (M.size() == NumElts * 2)
+      WhichResult = i / NumElts;
+    else
+      WhichResult = M[i] == 0 ? 0 : 1;
     unsigned Idx = WhichResult * NumElts / 2;
     for (unsigned j = 0; j < NumElts; j += 2) {
       if ((M[i+j] >= 0 && (unsigned) M[i+j] != Idx) ||
@@ -6005,7 +6014,10 @@ static bool isVZIP_v_undef_Mask(ArrayRef<int> M, EVT VT, unsigned &WhichResult){
     return false;
 
   for (unsigned i = 0; i < M.size(); i += NumElts) {
-    WhichResult = M[i] == 0 ? 0 : 1;
+    if (M.size() == NumElts * 2)
+      WhichResult = i / NumElts;
+    else
+      WhichResult = M[i] == 0 ? 0 : 1;
     unsigned Idx = WhichResult * NumElts / 2;
     for (unsigned j = 0; j < NumElts; j += 2) {
       if ((M[i+j] >= 0 && (unsigned) M[i+j] != Idx) ||
diff --git a/test/CodeGen/ARM/vzip.ll b/test/CodeGen/ARM/vzip.ll
index 771bf5f0521..06b49ab9405 100644
--- a/test/CodeGen/ARM/vzip.ll
+++ b/test/CodeGen/ARM/vzip.ll
@@ -282,6 +282,25 @@ entry:
   ret <8 x i16> %0
 }
 
+; NOTE: The mask here looks like something that could be done with a vzip,
+; but which the current handling of two-result vzip can't do - thus ending up
+; as a vtrn.
+define <8 x i16> @vzip_lower_shufflemask_undef_rev(<4 x i16>* %A, <4 x i16>* %B) {
+; CHECK-LABEL: vzip_lower_shufflemask_undef_rev:
+; CHECK:       @ BB#0: @ %entry
+; CHECK-NEXT:    vldr d16, [r1]
+; CHECK-NEXT:    vldr d19, [r0]
+; CHECK-NEXT:    vtrn.16 d19, d16
+; CHECK-NEXT:    vmov r0, r1, d18
+; CHECK-NEXT:    vmov r2, r3, d19
+; CHECK-NEXT:    mov pc, lr
+entry:
+  %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 undef, i32 undef, i32 undef, i32 0, i32 4, i32 undef, i32 undef>
+  ret <8 x i16> %0
+}
+
 define <4 x i32> @vzip_lower_shufflemask_zeroed(<2 x i32>* %A) {
 ; CHECK-LABEL: vzip_lower_shufflemask_zeroed:
 ; CHECK:       @ BB#0: @ %entry