[DAG] add (~a | x) & (a | y) -> (a & (x ^ y)) ^y for foldMaskedMerge

Author: woruyu

llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp

@@ -7206,24 +7206,30 @@ static SDValue foldLogicTreeOfShifts(SDNode *N, SDValue LeftHand,
   return DAG.getNode(LogicOpcode, DL, VT, CombinedShifts, W);
 }
 
-/// Fold "masked merge" expressions like `(m & x) | (~m & y)` into the
-/// equivalent `((x ^ y) & m) ^ y)` pattern.
-/// This is typically a better representation for targets without a fused
-/// "and-not" operation.
+/// Fold "masked merge" expressions like `(m & x) | (~m & y)` and its DeMorgan
+/// variant `(~m | x) & (m | y)` into the equivalent `((x ^ y) & m) ^ y)`
+/// pattern. This is typically a better representation for targets without a
+/// fused "and-not" operation.
 static SDValue foldMaskedMerge(SDNode *Node, SelectionDAG &DAG,
                                const TargetLowering &TLI, const SDLoc &DL) {
   // Note that masked-merge variants using XOR or ADD expressions are
-  // normalized to OR by InstCombine so we only check for OR.
-  assert(Node->getOpcode() == ISD::OR && "Must be called with ISD::OR node");
+  // normalized to OR by InstCombine so we only check for OR or AND.
+  assert(Node->getOpcode() == ISD::OR ||
+         Node->getOpcode() == ISD::AND &&
+             "Must be called with ISD::OR or ISD::AND node");
 
   // If the target supports and-not, don't fold this.
   if (TLI.hasAndNot(SDValue(Node, 0)))
     return SDValue();
 
   SDValue M, X, Y;
+
   if (sd_match(Node,
                m_Or(m_OneUse(m_And(m_OneUse(m_Not(m_Value(M))), m_Value(Y))),
-                    m_OneUse(m_And(m_Deferred(M), m_Value(X)))))) {
+                    m_OneUse(m_And(m_Deferred(M), m_Value(X))))) ||
+      sd_match(Node,
+               m_And(m_OneUse(m_Or(m_OneUse(m_Not(m_Value(M))), m_Value(X))),
+                     m_OneUse(m_Or(m_Deferred(M), m_Value(Y)))))) {
     EVT VT = M.getValueType();
     SDValue Xor = DAG.getNode(ISD::XOR, DL, VT, X, Y);
     SDValue And = DAG.getNode(ISD::AND, DL, VT, Xor, M);
@@ -7678,6 +7684,10 @@ SDValue DAGCombiner::visitAND(SDNode *N) {
     if (SDValue R = foldLogicTreeOfShifts(N, N0, N1, DAG))
       return R;
 
+  if (VT.isScalarInteger() && VT != MVT::i1)
+    if (SDValue R = foldMaskedMerge(N, DAG, TLI, DL))
+      return R;
+
   return SDValue();
 }
 

llvm/test/CodeGen/X86/fold-masked-merge-demorgan.ll

@@ -8,11 +8,10 @@
 define i32 @masked_merge0_demorgan(i32 %a0, i32 %a1, i32 %a2) {
 ; NOBMI-LABEL: masked_merge0_demorgan:
 ; NOBMI:       # %bb.0:
-; NOBMI-NEXT:    orl %edi, %edx
-; NOBMI-NEXT:    movl %edi, %eax
-; NOBMI-NEXT:    notl %eax
-; NOBMI-NEXT:    orl %esi, %eax
-; NOBMI-NEXT:    andl %edx, %eax
+; NOBMI-NEXT:    movl %esi, %eax
+; NOBMI-NEXT:    xorl %edx, %eax
+; NOBMI-NEXT:    andl %edi, %eax
+; NOBMI-NEXT:    xorl %edx, %eax
 ; NOBMI-NEXT:    retq
 ;
 ; BMI-LABEL: masked_merge0_demorgan:
@@ -29,15 +28,22 @@ define i32 @masked_merge0_demorgan(i32 %a0, i32 %a1, i32 %a2) {
 }
 
 define i16 @masked_merge1_demorgan(i16 %a0, i16 %a1, i16 %a2) {
-; CHECK-LABEL: masked_merge1_demorgan:
-; CHECK:       # %bb.0:
-; CHECK-NEXT:    orl %edi, %edx
-; CHECK-NEXT:    movl %edi, %eax
-; CHECK-NEXT:    notl %eax
-; CHECK-NEXT:    orl %esi, %eax
-; CHECK-NEXT:    andl %edx, %eax
-; CHECK-NEXT:    # kill: def $ax killed $ax killed $eax
-; CHECK-NEXT:    retq
+; NOBMI-LABEL: masked_merge1_demorgan:
+; NOBMI:       # %bb.0:
+; NOBMI-NEXT:    movl %esi, %eax
+; NOBMI-NEXT:    xorl %edx, %eax
+; NOBMI-NEXT:    andl %edi, %eax
+; NOBMI-NEXT:    xorl %edx, %eax
+; NOBMI-NEXT:    # kill: def $ax killed $ax killed $eax
+; NOBMI-NEXT:    retq
+;
+; BMI-LABEL: masked_merge1_demorgan:
+; BMI:       # %bb.0:
+; BMI-NEXT:    andnl %edx, %edi, %eax
+; BMI-NEXT:    andl %edi, %esi
+; BMI-NEXT:    orl %esi, %eax
+; BMI-NEXT:    # kill: def $ax killed $ax killed $eax
+; BMI-NEXT:    retq
   %not = xor i16 %a0, -1
   %or0 = or i16 %not, %a1
   %or1 = or i16 %a0, %a2
@@ -48,11 +54,8 @@ define i16 @masked_merge1_demorgan(i16 %a0, i16 %a1, i16 %a2) {
 define i8 @masked_merge2_demorgan(i8 %a0, i8 %a1, i8 %a2) {
 ; CHECK-LABEL: masked_merge2_demorgan:
 ; CHECK:       # %bb.0:
-; CHECK-NEXT:    movl %edi, %eax
-; CHECK-NEXT:    notb %al
-; CHECK-NEXT:    orb %sil, %al
-; CHECK-NEXT:    orb %sil, %dil
-; CHECK-NEXT:    andb %dil, %al
+; CHECK-NEXT:    movl %esi, %eax
+; CHECK-NEXT:    # kill: def $al killed $al killed $eax
 ; CHECK-NEXT:    retq
   %not = xor i8 %a0, -1
   %or0 = or i8 %not, %a1
@@ -64,13 +67,12 @@ define i8 @masked_merge2_demorgan(i8 %a0, i8 %a1, i8 %a2) {
 define i64 @masked_merge3_demorgan(i64 %a0, i64 %a1, i64 %a2) {
 ; NOBMI-LABEL: masked_merge3_demorgan:
 ; NOBMI:       # %bb.0:
+; NOBMI-NEXT:    movq %rsi, %rax
 ; NOBMI-NEXT:    notq %rdx
-; NOBMI-NEXT:    orq %rdi, %rdx
-; NOBMI-NEXT:    movq %rdi, %rax
+; NOBMI-NEXT:    xorq %rdx, %rax
 ; NOBMI-NEXT:    notq %rax
-; NOBMI-NEXT:    notq %rsi
-; NOBMI-NEXT:    orq %rsi, %rax
-; NOBMI-NEXT:    andq %rdx, %rax
+; NOBMI-NEXT:    andq %rdi, %rax
+; NOBMI-NEXT:    xorq %rdx, %rax
 ; NOBMI-NEXT:    retq
 ;
 ; BMI-LABEL: masked_merge3_demorgan: