[DAG] Optimize Constant Xor And And Not Operation

llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp

@@ -1262,6 +1262,27 @@ SDValue DAGCombiner::reassociateOpsCommutative(unsigned Opc, const SDLoc &DL,
     if (N1 == N00 || N1 == N01)
       return N0;
   }
+
+  // Optimize X & b & ~c -> X & (b & ~c) when ANDN is available
+  // This allows the ANDN operation to be done in parallel with computing X
+  if (Opc == ISD::AND && (TLI.hasAndNot(N1) || TLI.hasAndNot(N0)) &&
+      sd_match(N1, m_Not(m_Value()))) {
+    // Look for pattern: AND(AND(X, b), NOT(c))
+    // Transform to: AND(X, AND(b, NOT(c)))
+
+    SDValue X, B;
+
+    // Match AND(X, b) - check that N0 is an AND with one use
+    if (N0.getOpcode() == ISD::AND && N0->hasOneUse()) {
+      X = N00;
+      B = N01;
+
+      // Transform: AND(AND(X, b), NOT(c))
+      // To: AND(X, AND(b, NOT(c)))
+      SDValue AndBC = DAG.getNode(ISD::AND, DL, VT, B, N1);
+      return DAG.getNode(ISD::AND, DL, VT, X, AndBC);
+    }
+  }
   if (Opc == ISD::XOR) {
     // (N00 ^ N01) ^ N00 --> N01
     if (N1 == N00)
@@ -7518,6 +7539,52 @@ SDValue DAGCombiner::visitAND(SDNode *N) {
   if (SDValue NewSel = foldBinOpIntoSelect(N))
     return NewSel;
 
+  // Optimize (Constant XOR a) & b & ~c -> (Constant XOR a) & (b & ~c)
+  // This allows the andn operation to be done in parallel with the xor
+  if (TLI.hasAndNot(N1) || TLI.hasAndNot(N0)) {
+    SDValue InnerAndOp0, InnerAndOp1, NotArg;
+
+    // Match: AND(AND(Op0, Op1), NOT(NotArg))
+    // where NOT is represented as XOR with all-ones
+    // m_And automatically handles commutativity
+    if (sd_match(N, m_And(m_OneUse(m_And(m_Value(InnerAndOp0),
+                                         m_Value(InnerAndOp1))),
+                          m_Xor(m_Value(NotArg), m_AllOnes())))) {
+
+      // Determine which operand is XOR(Constant, X) where Constant is not
+      // all-ones
+      SDValue XorOp, OtherOp;
+      APInt XorConst;
+
+      // Try first operand - m_Xor handles commutativity for XOR operands
+      if (sd_match(InnerAndOp0, m_Xor(m_ConstInt(XorConst), m_Value())) &&
+          !XorConst.isAllOnes()) {
+        XorOp = InnerAndOp0;
+        OtherOp = InnerAndOp1;
+      } else if (sd_match(InnerAndOp1,
+                          m_Xor(m_ConstInt(XorConst), m_Value())) &&
+                 !XorConst.isAllOnes()) {
+        XorOp = InnerAndOp1;
+        OtherOp = InnerAndOp0;
+      } else {
+        // Pattern doesn't match - no XOR(Constant, X) found
+        XorOp = SDValue();
+      }
+
+      // If we found the pattern, apply the transformation
+      // Prevent infinite loops by checking OtherOp is not also a NOT
+      if (XorOp && !sd_match(OtherOp, m_Xor(m_Value(), m_AllOnes()))) {
+        // Get the NOT node (either N0 or N1)
+        SDValue NotOp = sd_match(N0, m_Xor(m_Value(), m_AllOnes())) ? N0 : N1;
+
+        // Transform: AND(AND(XOR(Constant, a), b), NOT(c))
+        // To: AND(XOR(Constant, a), AND(b, NOT(c)))
+        SDValue NewAnd = DAG.getNode(ISD::AND, DL, VT, OtherOp, NotOp);
+        return DAG.getNode(ISD::AND, DL, VT, XorOp, NewAnd);
+      }
+    }
+  }
+
   // reassociate and
   if (SDValue RAND = reassociateOps(ISD::AND, DL, N0, N1, N->getFlags()))
     return RAND;

llvm/test/CodeGen/X86/andn-reassociate.ll

@@ -0,0 +1,124 @@
+; NOTE: Assertions have been autogenerated by utils/update_llc_test_checks.py
+; RUN: llc -mtriple=x86_64-unknown-unknown -mattr=-bmi < %s | FileCheck %s --check-prefixes=CHECK,NOBMI
+; RUN: llc -mtriple=x86_64-unknown-unknown -mattr=+bmi < %s | FileCheck %s --check-prefixes=CHECK,BMI
+
+; Test the optimization: X & b & ~c -> X & (b & ~c)
+; This reassociation allows ANDN to execute in parallel with computing X
+
+define i64 @test_constant_xor_and_andnot(i64 %a, i64 %b, i64 %c) {
+; NOBMI-LABEL: test_constant_xor_and_andnot:
+; NOBMI:       # %bb.0:
+; NOBMI-NEXT:    movq %rdx, %rax
+; NOBMI-NEXT:    xorq $1234, %rdi # imm = 0x4D2
+; NOBMI-NEXT:    andq %rsi, %rdi
+; NOBMI-NEXT:    notq %rax
+; NOBMI-NEXT:    andq %rdi, %rax
+; NOBMI-NEXT:    retq
+;
+; BMI-LABEL: test_constant_xor_and_andnot:
+; BMI:       # %bb.0:
+; BMI-NEXT:    xorq $1234, %rdi # imm = 0x4D2
+; BMI-NEXT:    andnq %rsi, %rdx, %rax
+; BMI-NEXT:    andq %rdi, %rax
+; BMI-NEXT:    retq
+  %xor = xor i64 %a, 1234
+  %and1 = and i64 %xor, %b
+  %not_c = xor i64 %c, -1
+  %result = and i64 %and1, %not_c
+  ret i64 %result
+}
+
+define i32 @test_constant_xor_and_andnot_32(i32 %a, i32 %b, i32 %c) {
+; NOBMI-LABEL: test_constant_xor_and_andnot_32:
+; NOBMI:       # %bb.0:
+; NOBMI-NEXT:    movl %edx, %eax
+; NOBMI-NEXT:    xorl $5678, %edi # imm = 0x162E
+; NOBMI-NEXT:    andl %esi, %edi
+; NOBMI-NEXT:    notl %eax
+; NOBMI-NEXT:    andl %edi, %eax
+; NOBMI-NEXT:    retq
+;
+; BMI-LABEL: test_constant_xor_and_andnot_32:
+; BMI:       # %bb.0:
+; BMI-NEXT:    xorl $5678, %edi # imm = 0x162E
+; BMI-NEXT:    andnl %esi, %edx, %eax
+; BMI-NEXT:    andl %edi, %eax
+; BMI-NEXT:    retq
+  %xor = xor i32 %a, 5678
+  %and1 = and i32 %xor, %b
+  %not_c = xor i32 %c, -1
+  %result = and i32 %and1, %not_c
+  ret i32 %result
+}
+
+; Test with different operand order
+define i64 @test_constant_xor_and_andnot_swapped(i64 %a, i64 %b, i64 %c) {
+; NOBMI-LABEL: test_constant_xor_and_andnot_swapped:
+; NOBMI:       # %bb.0:
+; NOBMI-NEXT:    movq %rdx, %rax
+; NOBMI-NEXT:    xorq $1234, %rdi # imm = 0x4D2
+; NOBMI-NEXT:    andq %rsi, %rdi
+; NOBMI-NEXT:    notq %rax
+; NOBMI-NEXT:    andq %rdi, %rax
+; NOBMI-NEXT:    retq
+;
+; BMI-LABEL: test_constant_xor_and_andnot_swapped:
+; BMI:       # %bb.0:
+; BMI-NEXT:    xorq $1234, %rdi # imm = 0x4D2
+; BMI-NEXT:    andnq %rsi, %rdx, %rax
+; BMI-NEXT:    andq %rdi, %rax
+; BMI-NEXT:    retq
+  %xor = xor i64 %a, 1234
+  %and1 = and i64 %b, %xor
+  %not_c = xor i64 %c, -1
+  %result = and i64 %and1, %not_c
+  ret i64 %result
+}
+
+; Test with different operand order for the final AND
+define i64 @test_constant_xor_and_andnot_final_swapped(i64 %a, i64 %b, i64 %c) {
+; NOBMI-LABEL: test_constant_xor_and_andnot_final_swapped:
+; NOBMI:       # %bb.0:
+; NOBMI-NEXT:    movq %rdx, %rax
+; NOBMI-NEXT:    xorq $1234, %rdi # imm = 0x4D2
+; NOBMI-NEXT:    andq %rsi, %rdi
+; NOBMI-NEXT:    notq %rax
+; NOBMI-NEXT:    andq %rdi, %rax
+; NOBMI-NEXT:    retq
+;
+; BMI-LABEL: test_constant_xor_and_andnot_final_swapped:
+; BMI:       # %bb.0:
+; BMI-NEXT:    xorq $1234, %rdi # imm = 0x4D2
+; BMI-NEXT:    andnq %rsi, %rdx, %rax
+; BMI-NEXT:    andq %rdi, %rax
+; BMI-NEXT:    retq
+  %xor = xor i64 %a, 1234
+  %and1 = and i64 %xor, %b
+  %not_c = xor i64 %c, -1
+  %result = and i64 %not_c, %and1
+  ret i64 %result
+}
+
+define i64 @test_add_and_andnot(i64 %a, i64 %b, i64 %c) {
+; NOBMI-LABEL: test_add_and_andnot:
+; NOBMI:       # %bb.0:
+; NOBMI-NEXT:    leaq 5678(%rdi), %rax
+; NOBMI-NEXT:    andq %rsi, %rax
+; NOBMI-NEXT:    notq %rdx
+; NOBMI-NEXT:    andq %rdx, %rax
+; NOBMI-NEXT:    retq
+;
+; BMI-LABEL: test_add_and_andnot:
+; BMI:       # %bb.0:
+; BMI-NEXT:    leaq 5678(%rdi), %rcx
+; BMI-NEXT:    andnq %rsi, %rdx, %rax
+; BMI-NEXT:    andq %rcx, %rax
+; BMI-NEXT:    retq
+  %add = add i64 %a, 5678
+  %and1 = and i64 %add, %b
+  %not_c = xor i64 %c, -1
+  %result = and i64 %and1, %not_c
+  ret i64 %result
+}
+;; NOTE: These prefixes are unused and the list is autogenerated. Do not add tests below this line:
+; CHECK: {{.*}}

llvm/test/CodeGen/X86/pr108731.ll

@@ -17,9 +17,9 @@ define i64 @test_i64(i64 %w, i64 %x, i64 %y, i64 %z) {
 ; BMI-LABEL: test_i64:
 ; BMI:       # %bb.0: # %Entry
 ; BMI-NEXT:    andq %rdx, %rsi
-; BMI-NEXT:    andnq %rdi, %rsi, %rax
-; BMI-NEXT:    andnq %rcx, %rdx, %rcx
-; BMI-NEXT:    andnq %rax, %rcx, %rax
+; BMI-NEXT:    andnq %rcx, %rdx, %rax
+; BMI-NEXT:    andnq %rdi, %rax, %rax
+; BMI-NEXT:    andnq %rax, %rsi, %rax
 ; BMI-NEXT:    retq
 Entry:
   %and1 = and i64 %y, %x
@@ -46,9 +46,9 @@ define i32 @test_i32(i32 %w, i32 %x, i32 %y, i32 %z) {
 ; BMI-LABEL: test_i32:
 ; BMI:       # %bb.0: # %Entry
 ; BMI-NEXT:    andl %edx, %esi
-; BMI-NEXT:    andnl %edi, %esi, %eax
-; BMI-NEXT:    andnl %ecx, %edx, %ecx
-; BMI-NEXT:    andnl %eax, %ecx, %eax
+; BMI-NEXT:    andnl %ecx, %edx, %eax
+; BMI-NEXT:    andnl %edi, %eax, %eax
+; BMI-NEXT:    andnl %eax, %esi, %eax
 ; BMI-NEXT:    retq
 Entry:
   %and1 = and i32 %y, %x