From a41537373a34a765bff6d92ebfd21e088e9308d1 Mon Sep 17 00:00:00 2001
From: Sanjay Patel <spatel@rotateright.com>
Date: Sun, 6 Oct 2019 15:27:34 +0000
Subject: [PATCH] Revert [DAGCombine] Match more patterns for half word bswap

This reverts r373850 (git commit 25ba49824d2d4f2347b4a7cb1623600a76ce9433)

This patch appears to cause multiple codegen regression test failures - http://lab.llvm.org:8011/builders/clang-cmake-armv7-quick/builds/10680

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@373853 91177308-0d34-0410-b5e6-96231b3b80d8
---
 lib/CodeGen/SelectionDAG/DAGCombiner.cpp | 58 ++++++++++++------------
 test/CodeGen/X86/bswap_tree.ll           | 21 +++++++--
 2 files changed, 47 insertions(+), 32 deletions(-)

diff --git a/lib/CodeGen/SelectionDAG/DAGCombiner.cpp b/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
index ea73ff865bf..38fd9742d2d 100644
--- a/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
+++ b/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
@@ -5517,23 +5517,6 @@ static bool isBSwapHWordElement(SDValue N, MutableArrayRef<SDNode *> Parts) {
   return true;
 }
 
-// Match 2 elements of a packed halfword bswap.
-static bool isBSwapHWordPair(SDValue N, MutableArrayRef<SDNode *> Parts) {
-  if (N.getOpcode() == ISD::OR)
-    return isBSwapHWordElement(N.getOperand(0), Parts) &&
-           isBSwapHWordElement(N.getOperand(1), Parts);
-
-  if (N.getOpcode() == ISD::SRL && N.getOperand(0).getOpcode() == ISD::BSWAP) {
-    ConstantSDNode *C = isConstOrConstSplat(N.getOperand(1));
-    if (!C || C->getAPIntValue() != 16)
-      return false;
-    Parts[0] = Parts[1] = N.getOperand(0).getOperand(0).getNode();
-    return true;
-  }
-
-  return false;
-}
-
 /// Match a 32-bit packed halfword bswap. That is
 /// ((x & 0x000000ff) << 8) |
 /// ((x & 0x0000ff00) >> 8) |
@@ -5551,26 +5534,43 @@ SDValue DAGCombiner::MatchBSwapHWord(SDNode *N, SDValue N0, SDValue N1) {
     return SDValue();
 
   // Look for either
-  // (or (bswaphpair), (bswaphpair))
-  // (or (or (bswaphpair), (and)), (and))
-  // (or (or (and), (bswaphpair)), (and))
+  // (or (or (and), (and)), (or (and), (and)))
+  // (or (or (or (and), (and)), (and)), (and))
+  if (N0.getOpcode() != ISD::OR)
+    return SDValue();
+  SDValue N00 = N0.getOperand(0);
+  SDValue N01 = N0.getOperand(1);
   SDNode *Parts[4] = {};
 
-  if (isBSwapHWordPair(N0, Parts)) {
+  if (N1.getOpcode() == ISD::OR &&
+      N00.getNumOperands() == 2 && N01.getNumOperands() == 2) {
     // (or (or (and), (and)), (or (and), (and)))
-    if (!isBSwapHWordPair(N1, Parts))
+    if (!isBSwapHWordElement(N00, Parts))
+      return SDValue();
+
+    if (!isBSwapHWordElement(N01, Parts))
+      return SDValue();
+    SDValue N10 = N1.getOperand(0);
+    if (!isBSwapHWordElement(N10, Parts))
+      return SDValue();
+    SDValue N11 = N1.getOperand(1);
+    if (!isBSwapHWordElement(N11, Parts))
       return SDValue();
-  } else if (N0.getOpcode() != ISD::OR) {
+  } else {
     // (or (or (or (and), (and)), (and)), (and))
     if (!isBSwapHWordElement(N1, Parts))
       return SDValue();
-    SDValue N00 = N0.getOperand(0);
-    SDValue N01 = N0.getOperand(1);
-    if (!(isBSwapHWordElement(N01, Parts) && isBSwapHWordPair(N00, Parts)) &&
-        !(isBSwapHWordElement(N00, Parts) && isBSwapHWordPair(N01, Parts)))
+    if (!isBSwapHWordElement(N01, Parts))
       return SDValue();
-  } else
-    return SDValue();
+    if (N00.getOpcode() != ISD::OR)
+      return SDValue();
+    SDValue N000 = N00.getOperand(0);
+    if (!isBSwapHWordElement(N000, Parts))
+      return SDValue();
+    SDValue N001 = N00.getOperand(1);
+    if (!isBSwapHWordElement(N001, Parts))
+      return SDValue();
+  }
 
   // Make sure the parts are all coming from the same node.
   if (Parts[0] != Parts[1] || Parts[0] != Parts[2] || Parts[0] != Parts[3])
diff --git a/test/CodeGen/X86/bswap_tree.ll b/test/CodeGen/X86/bswap_tree.ll
index b136263b179..79a45050b98 100644
--- a/test/CodeGen/X86/bswap_tree.ll
+++ b/test/CodeGen/X86/bswap_tree.ll
@@ -79,15 +79,30 @@ define i32 @test3(i32 %x) nounwind {
 ; CHECK-LABEL: test3:
 ; CHECK:       # %bb.0:
 ; CHECK-NEXT:    movl {{[0-9]+}}(%esp), %eax
+; CHECK-NEXT:    movl %eax, %ecx
+; CHECK-NEXT:    andl $16711680, %ecx # imm = 0xFF0000
+; CHECK-NEXT:    movl %eax, %edx
+; CHECK-NEXT:    andl $-16777216, %edx # imm = 0xFF000000
+; CHECK-NEXT:    shll $8, %ecx
+; CHECK-NEXT:    shrl $8, %edx
+; CHECK-NEXT:    orl %ecx, %edx
 ; CHECK-NEXT:    bswapl %eax
-; CHECK-NEXT:    roll $16, %eax
+; CHECK-NEXT:    shrl $16, %eax
+; CHECK-NEXT:    orl %edx, %eax
 ; CHECK-NEXT:    retl
 ;
 ; CHECK64-LABEL: test3:
 ; CHECK64:       # %bb.0:
 ; CHECK64-NEXT:    movl %edi, %eax
-; CHECK64-NEXT:    bswapl %eax
-; CHECK64-NEXT:    roll $16, %eax
+; CHECK64-NEXT:    andl $16711680, %eax # imm = 0xFF0000
+; CHECK64-NEXT:    movl %edi, %ecx
+; CHECK64-NEXT:    andl $-16777216, %ecx # imm = 0xFF000000
+; CHECK64-NEXT:    shll $8, %eax
+; CHECK64-NEXT:    shrl $8, %ecx
+; CHECK64-NEXT:    addl %ecx, %eax
+; CHECK64-NEXT:    bswapl %edi
+; CHECK64-NEXT:    shrl $16, %edi
+; CHECK64-NEXT:    orl %edi, %eax
 ; CHECK64-NEXT:    retq
   %byte2 = and i32 %x, 16711680   ; 0x00ff0000
   %byte3 = and i32 %x, 4278190080 ; 0xff000000
-- 
2.40.0