[AArch64] Lower disjoint_or+not to eon. (#147279)

A disjoint OR can be transformed to an EOR.

We already lower EOR+NOT to EON, but not DisjointOR+NOT.

llvm/include/llvm/Target/TargetSelectionDAG.td

@@ -1140,6 +1140,19 @@ def not  : PatFrag<(ops node:$in), (xor node:$in, -1)>;
 def vnot : PatFrag<(ops node:$in), (xor node:$in, immAllOnesV)>;
 def ineg : PatFrag<(ops node:$in), (sub 0, node:$in)>;
 
+def or_disjoint : PatFrag<(ops node:$lhs, node:$rhs),
+                          (or node:$lhs, node:$rhs), [{
+  return N->getFlags().hasDisjoint();
+}]> {
+  let GISelPredicateCode = [{
+    return MI.getFlag(MachineInstr::Disjoint);
+  }];
+}
+
+def xor_like : PatFrags<(ops node:$lhs, node:$rhs),
+                        [(xor node:$lhs, node:$rhs),
+                         (or_disjoint node:$lhs, node:$rhs)]>;
+
 def zanyext : PatFrags<(ops node:$op),
                        [(zext node:$op),
                         (anyext node:$op)]>;

llvm/lib/Target/AArch64/AArch64InstrInfo.td

@@ -3118,7 +3118,7 @@ defm AND  : LogicalReg<0b00, 0, "and", and>;
 defm BIC  : LogicalReg<0b00, 1, "bic",
                        BinOpFrag<(and node:$LHS, (not node:$RHS))>, 3>;
 defm EON  : LogicalReg<0b10, 1, "eon",
-                       BinOpFrag<(not (xor node:$LHS, node:$RHS))>>;
+                       BinOpFrag<(not (xor_like node:$LHS, node:$RHS))>>;
 defm EOR  : LogicalReg<0b10, 0, "eor", xor>;
 defm ORN  : LogicalReg<0b01, 1, "orn",
                        BinOpFrag<(or node:$LHS, (not node:$RHS))>>;

llvm/test/CodeGen/AArch64/eon.ll

@@ -30,3 +30,24 @@ entry:
   %shl2 = shl i64 %xor, %xor1
   ret i64 %shl2
 }
+
+; Check that eon is generated if the xor is a disjoint or.
+define i64 @disjoint_or(i64 %a, i64 %b) {
+; CHECK-LABEL: disjoint_or:
+; CHECK: eon
+; CHECK: ret
+  %or = or disjoint i64 %a, %b
+  %eon = xor i64 %or, -1
+  ret i64 %eon
+}
+
+; Check that eon is *not* generated if the or is not disjoint.
+define i64 @normal_or(i64 %a, i64 %b) {
+; CHECK-LABEL: normal_or:
+; CHECK: orr
+; CHECK: mvn
+; CHECK: ret
+  %or = or i64 %a, %b
+  %not = xor i64 %or, -1
+  ret i64 %not
+}

llvm/test/TableGen/GlobalISelEmitter/CustomPredicate.td

@@ -6,6 +6,7 @@
 // CHECK-NEXT: enum {
 // CHECK-NEXT:   GICXXPred_MI_Predicate_and_or_pat = GICXXPred_Invalid + 1,
 // CHECK-NEXT:   GICXXPred_MI_Predicate_mul_pat,
+// CHECK-NEXT:   GICXXPred_MI_Predicate_or_disjoint,
 // CHECK-NEXT:   GICXXPred_MI_Predicate_or_oneuse,
 // CHECK-NEXT:   GICXXPred_MI_Predicate_patfrags_test_pat,
 // CHECK-NEXT:   GICXXPred_MI_Predicate_sub3_pat,

llvm/test/TableGen/GlobalISelEmitter/GlobalISelEmitter.td

@@ -156,6 +156,7 @@ def HasC : Predicate<"Subtarget->hasC()"> { let RecomputePerFunction = 1; }
 // CHECK-LABEL: // PatFrag predicates.
 // CHECK-NEXT:  enum {
 // CHECK-NEXT:   GICXXPred_MI_Predicate_frag = GICXXPred_Invalid + 1,
+// CHECK-NEXT:   GICXXPred_MI_Predicate_or_disjoint,
 // CHECK-NEXT:  };
 
 // CHECK-LABEL: // PatFrag predicates.