[TableGen] Add a backend to generate MacroFusion predicators

`FusionPredicate` is used to predicate if target instruction matches
the requirement. The targets can be firstMI, secondMI or both.

The `Fusion` contains a list of `FusionPredicate`. The generated code
will be like:
```
bool isNAME(const TargetInstrInfo &TII,
            const TargetSubtargetInfo &STI,
            const MachineInstr *FirstMI,
            const MachineInstr &SecondMI) {
  auto &MRI = SecondMI.getMF()->getRegInfo();
  /* Predicates */
  return true;
}
```

A boilerplate class called `SimpleFusion` is added. `SimpleFusion` has
a predefined structure of predicates and accepts predicate for
`firstMI`, predicate for `secondMI` and epilog/prolog as arguments.
The generated code for `SimpleFusion` will be like:
```
bool isNAME(const TargetInstrInfo &TII,
            const TargetSubtargetInfo &STI,
            const MachineInstr *FirstMI,
            const MachineInstr &SecondMI) {
  auto &MRI = SecondMI.getMF()->getRegInfo();
  /* Prolog */
  /* Predicate for `SecondMI` */
  /* Wildcard */
  /* Predicate for `FirstMI` */
  /* Check One Use */
  /* Tie registers */
  /* Epilog */
  return true;
}
```

llvm/include/llvm/Target/TargetInstrPredicate.td

@@ -95,6 +95,12 @@ class MCOperandPredicate<int Index> : MCInstPredicate {
 // Return true if machine operand at position `Index` is a register operand.
 class CheckIsRegOperand<int Index> : MCOperandPredicate<Index>;
 
+// Return true if machine operand at position `Index` is a virtual register operand.
+class CheckIsVRegOperand<int Index> : MCOperandPredicate<Index>;
+
+// Return true if machine operand at position `Index` is not a virtual register operand.
+class CheckIsNotVRegOperand<int Index> : CheckNot<CheckIsVRegOperand<Index>>;
+
 // Return true if machine operand at position `Index` is an immediate operand.
 class CheckIsImmOperand<int Index> : MCOperandPredicate<Index>;
 

llvm/include/llvm/Target/TargetSchedule.td

@@ -584,3 +584,116 @@ class MemoryQueue<ProcResourceKind PR> {
 
 class LoadQueue<ProcResourceKind LDQueue> : MemoryQueue<LDQueue>;
 class StoreQueue<ProcResourceKind STQueue> : MemoryQueue<STQueue>;
+
+// The target instruction that FusionPredicate will be evaluated on.
+class FusionTarget;
+def first_fusion_target : FusionTarget;
+def second_fusion_target : FusionTarget;
+def both_fusion_target : FusionTarget;
+
+// Base class of FusionPredicate, etc. The avaliable variables are:
+// * const TargetInstrInfo &TII
+// * const TargetSubtargetInfo &STI
+// * const MachineRegisterInfo &MRI
+// * const MachineInstr *FirstMI
+// * const MachineInstr &SecondMI
+class FusionPredicate<FusionTarget target> {
+  FusionTarget Target = target;
+}
+class FirstFusionPredicate: FusionPredicate<first_fusion_target>;
+class SecondFusionPredicate: FusionPredicate<second_fusion_target>;
+class BothFusionPredicate: FusionPredicate<both_fusion_target>;
+
+// FusionPredicate with raw code predicate.
+class FusionPredicateWithCode<code pred> : FusionPredicate<both_fusion_target> {
+  code Predicate = pred;
+}
+
+// FusionPredicate with MCInstPredicate.
+class FusionPredicateWithMCInstPredicate<FusionTarget target, MCInstPredicate pred>
+  : FusionPredicate<target> {
+  MCInstPredicate Predicate = pred;
+}
+class FirstFusionPredicateWithMCInstPredicate<MCInstPredicate pred>
+  : FusionPredicateWithMCInstPredicate<first_fusion_target, pred>;
+class SecondFusionPredicateWithMCInstPredicate<MCInstPredicate pred>
+  : FusionPredicateWithMCInstPredicate<second_fusion_target, pred>;
+// The pred will be applied on both firstMI and secondMI.
+class BothFusionPredicateWithMCInstPredicate<MCInstPredicate pred>
+  : FusionPredicateWithMCInstPredicate<second_fusion_target, pred>;
+
+// Tie firstOpIdx and secondOpIdx. The operand of `FirstMI` at position
+// `firstOpIdx` should be the same as the operand of `SecondMI` at position
+// `secondOpIdx`.
+class TieReg<int firstOpIdx, int secondOpIdx> : BothFusionPredicate {
+  int FirstOpIdx = firstOpIdx;
+  int SecondOpIdx = secondOpIdx;
+}
+
+// A predicate for wildcard. The generated code will be like:
+// ```
+// if (!FirstMI)
+//   return ReturnValue;
+// ```
+class WildcardPred<bit ret> : FirstFusionPredicate {
+  bit ReturnValue = ret;
+}
+def WildcardFalse : WildcardPred<0>;
+def WildcardTrue : WildcardPred<1>;
+
+// Indicates that the destination register of `FirstMI` should have one use if
+// it is a virtual register.
+class OneUsePred : FirstFusionPredicate;
+def OneUse : OneUsePred;
+
+// Handled by MacroFusionPredicatorEmitter backend.
+// The generated predicator will be like:
+// ```
+// bool isNAME(const TargetInstrInfo &TII,
+//             const TargetSubtargetInfo &STI,
+//             const MachineInstr *FirstMI,
+//             const MachineInstr &SecondMI) {
+//   auto &MRI = SecondMI.getMF()->getRegInfo();
+//   /* Predicates */
+//   return true;
+// }
+// ```
+class Fusion<list<FusionPredicate> predicates> {
+  list<FusionPredicate> Predicates = predicates;
+}
+
+// The generated predicator will be like:
+// ```
+// bool isNAME(const TargetInstrInfo &TII,
+//             const TargetSubtargetInfo &STI,
+//             const MachineInstr *FirstMI,
+//             const MachineInstr &SecondMI) {
+//   auto &MRI = SecondMI.getMF()->getRegInfo();
+//   /* Prolog */
+//   /* Predicate for `SecondMI` */
+//   /* Wildcard */
+//   /* Predicate for `FirstMI` */
+//   /* Check One Use */
+//   /* Tie registers */
+//   /* Epilog */
+//   return true;
+// }
+// ```
+class SimpleFusion<MCInstPredicate firstPred, MCInstPredicate secondPred,
+                   list<FusionPredicate> prolog = [],
+                   list<FusionPredicate> epilog = []>
+  : Fusion<!listconcat(
+                  prolog,
+                  [
+                    SecondFusionPredicateWithMCInstPredicate<secondPred>,
+                    WildcardTrue,
+                    FirstFusionPredicateWithMCInstPredicate<firstPred>,
+                    SecondFusionPredicateWithMCInstPredicate<
+                      CheckAny<[
+                        CheckIsVRegOperand<0>,
+                        CheckSameRegOperand<0, 1>
+                      ]>>,
+                    OneUse,
+                    TieReg<0, 1>,
+                  ],
+                  epilog)>;

llvm/test/TableGen/MacroFusion.td

@@ -0,0 +1,97 @@
+// RUN: llvm-tblgen -gen-macro-fusion-pred -I %p/../../include %s | FileCheck %s --check-prefix=CHECK-PREDICATOR
+
+include "llvm/Target/Target.td"
+
+def TestInstrInfo : InstrInfo { }
+def TestAsmWriter : AsmWriter {
+  int PassSubtarget = 1;
+}
+
+def Test : Target {
+  let InstructionSet = TestInstrInfo;
+  let AssemblyWriters = [TestAsmWriter];
+}
+
+let Namespace = "Test" in {
+  foreach i = 0-32 in {
+    def X#i : Register<"x"#i>;
+  }
+
+  def GPR : RegisterClass<"GPR", [i32], 32, (sequence  "X%u", 0, 32)>;
+
+  class TestInst<int Opc> : Instruction {
+    field bits<32> Inst;
+    field bits<32> SoftFail = 0;
+    let Size = 4;
+    let Inst = Opc;
+    let OutOperandList = (outs);
+    let InOperandList = (ins);
+    let AsmString = NAME;
+  }
+}
+
+def Inst0 : TestInst<0>;
+def Inst1 : TestInst<1>;
+
+def TestFusion: SimpleFusion<CheckOpcode<[Inst0]>,
+                             CheckAll<[
+                              CheckOpcode<[Inst1]>,
+                              CheckRegOperand<0, X0>
+                             ]>>;
+
+// CHECK-PREDICATOR:       #ifdef GET_Test_MACRO_FUSION_PRED_DECL
+// CHECK-PREDICATOR-NEXT:  #undef GET_Test_MACRO_FUSION_PRED_DECL
+// CHECK-PREDICATOR-EMPTY:
+// CHECK-PREDICATOR-NEXT:  namespace llvm {
+// CHECK-PREDICATOR-NEXT:  bool isTestFusion(const TargetInstrInfo &, const TargetSubtargetInfo &, const MachineInstr *, const MachineInstr &);
+// CHECK-PREDICATOR-NEXT:  } // end namespace llvm
+// CHECK-PREDICATOR-EMPTY:
+// CHECK-PREDICATOR-NEXT:  #endif
+
+// CHECK-PREDICATOR:       #ifdef GET_Test_MACRO_FUSION_PRED_IMPL
+// CHECK-PREDICATOR-NEXT:  #undef GET_Test_MACRO_FUSION_PRED_IMPL
+// CHECK-PREDICATOR-EMPTY:
+// CHECK-PREDICATOR-NEXT:  namespace llvm {
+// CHECK-PREDICATOR-NEXT:  bool isTestFusion(
+// CHECK-PREDICATOR-NEXT:       const TargetInstrInfo &TII,
+// CHECK-PREDICATOR-NEXT:       const TargetSubtargetInfo &STI,
+// CHECK-PREDICATOR-NEXT:       const MachineInstr *FirstMI,
+// CHECK-PREDICATOR-NEXT:       const MachineInstr &SecondMI) {
+// CHECK-PREDICATOR-NEXT:    auto &MRI = SecondMI.getMF()->getRegInfo();
+// CHECK-PREDICATOR-NEXT:    {
+// CHECK-PREDICATOR-NEXT:      const MachineInstr *MI = &SecondMI;
+// CHECK-PREDICATOR-NEXT:      if (!(
+// CHECK-PREDICATOR-NEXT:          ( MI->getOpcode() == Test::Inst1 )
+// CHECK-PREDICATOR-NEXT:          && MI->getOperand(0).getReg() == Test::X0
+// CHECK-PREDICATOR-NEXT:        ))
+// CHECK-PREDICATOR-NEXT:        return false;
+// CHECK-PREDICATOR-NEXT:    }
+// CHECK-PREDICATOR-NEXT:    if (!FirstMI)
+// CHECK-PREDICATOR-NEXT:      return true;
+// CHECK-PREDICATOR-NEXT:    {
+// CHECK-PREDICATOR-NEXT:      const MachineInstr *MI = FirstMI;
+// CHECK-PREDICATOR-NEXT:      if (( MI->getOpcode() != Test::Inst0 ))
+// CHECK-PREDICATOR-NEXT:        return false;
+// CHECK-PREDICATOR-NEXT:    }
+// CHECK-PREDICATOR-NEXT:    {
+// CHECK-PREDICATOR-NEXT:      const MachineInstr *MI = &SecondMI;
+// CHECK-PREDICATOR-NEXT:      if (!(
+// CHECK-PREDICATOR-NEXT:          MI->getOperand(0).getReg().isVirtual()
+// CHECK-PREDICATOR-NEXT:          || MI->getOperand(0).getReg() == MI->getOperand(1).getReg()
+// CHECK-PREDICATOR-NEXT:        ))
+// CHECK-PREDICATOR-NEXT:        return false;
+// CHECK-PREDICATOR-NEXT:    }
+// CHECK-PREDICATOR-NEXT:    {
+// CHECK-PREDICATOR-NEXT:      Register FirstDest = FirstMI->getOperand(0).getReg();
+// CHECK-PREDICATOR-NEXT:      if (FirstDest.isVirtual() && !MRI.hasOneNonDBGUse(FirstDest))
+// CHECK-PREDICATOR-NEXT:        return false;
+// CHECK-PREDICATOR-NEXT:    }
+// CHECK-PREDICATOR-NEXT:    if (!(FirstMI->getOperand(0).isReg() &&
+// CHECK-PREDICATOR-NEXT:          SecondMI.getOperand(1).isReg() &&
+// CHECK-PREDICATOR-NEXT:          FirstMI->getOperand(0).getReg() == SecondMI.getOperand(1).getReg()))
+// CHECK-PREDICATOR-NEXT:      return false;
+// CHECK-PREDICATOR-NEXT:    return true;
+// CHECK-PREDICATOR-NEXT:  }
+// CHECK-PREDICATOR-NEXT:  } // end namespace llvm
+// CHECK-PREDICATOR-EMPTY:
+// CHECK-PREDICATOR-NEXT:  #endif

llvm/utils/TableGen/CMakeLists.txt

@@ -72,6 +72,7 @@ add_tablegen(llvm-tblgen LLVM
   PredicateExpander.cpp
   PseudoLoweringEmitter.cpp
   CompressInstEmitter.cpp
+  MacroFusionPredicatorEmitter.cpp
   RegisterBankEmitter.cpp
   RegisterInfoEmitter.cpp
   SearchableTableEmitter.cpp