Add isRegSequence property.

This patch adds a new property: isRegSequence and the related target hooks: 
TargetIntrInfo::getRegSequenceInputs and 
TargetInstrInfo::getRegSequenceLikeInputs to specify that a target specific
instruction is a (kind of) REG_SEQUENCE.

<rdar://problem/12702965>


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@215394 91177308-0d34-0410-b5e6-96231b3b80d8

include/llvm/CodeGen/MachineInstr.h

@@ -510,6 +510,20 @@ public:
     return hasProperty(MCID::FoldableAsLoad, Type);
   }
 
+  /// \brief Return true if this instruction behaves
+  /// the same way as the generic REG_SEQUENCE instructions.
+  /// E.g., on ARM,
+  /// dX VMOVDRR rY, rZ
+  /// is equivalent to
+  /// dX = REG_SEQUENCE rY, ssub_0, rZ, ssub_1.
+  ///
+  /// Note that for the optimizers to be able to take advantage of
+  /// this property, TargetInstrInfo::getRegSequenceLikeInputs has to be
+  /// override accordingly.
+  bool isRegSequenceLike(QueryType Type = IgnoreBundle) const {
+    return hasProperty(MCID::RegSequence, Type);
+  }
+
   //===--------------------------------------------------------------------===//
   // Side Effect Analysis
   //===--------------------------------------------------------------------===//

include/llvm/MC/MCInstrDesc.h

@@ -125,7 +125,8 @@ namespace MCID {
     Rematerializable,
     CheapAsAMove,
     ExtraSrcRegAllocReq,
-    ExtraDefRegAllocReq
+    ExtraDefRegAllocReq,
+    RegSequence
   };
 }
 
@@ -357,6 +358,18 @@ public:
     return Flags & (1 << MCID::FoldableAsLoad);
   }
 
+  /// \brief Return true if this instruction behaves
+  /// the same way as the generic REG_SEQUENCE instructions.
+  /// E.g., on ARM,
+  /// dX VMOVDRR rY, rZ
+  /// is equivalent to
+  /// dX = REG_SEQUENCE rY, ssub_0, rZ, ssub_1.
+  ///
+  /// Note that for the optimizers to be able to take advantage of
+  /// this property, TargetInstrInfo::getRegSequenceLikeInputs has to be
+  /// override accordingly.
+  bool isRegSequenceLike() const { return Flags & (1 << MCID::RegSequence); }
+
   //===--------------------------------------------------------------------===//
   // Side Effect Analysis
   //===--------------------------------------------------------------------===//

include/llvm/Target/Target.td

@@ -378,6 +378,9 @@ class Instruction {
   bit isAsCheapAsAMove = 0; // As cheap (or cheaper) than a move instruction.
   bit hasExtraSrcRegAllocReq = 0; // Sources have special regalloc requirement?
   bit hasExtraDefRegAllocReq = 0; // Defs have special regalloc requirement?
+  bit isRegSequence = 0;    // Is this instruction a kind of reg sequence?
+                            // If so, make sure to override
+                            // TargetInstrInfo::getRegSequenceLikeInputs.
   bit isPseudo     = 0;     // Is this instruction a pseudo-instruction?
                             // If so, won't have encoding information for
                             // the [MC]CodeEmitter stuff.

include/llvm/Target/TargetInstrInfo.h

@@ -264,6 +264,45 @@ public:
   virtual bool findCommutedOpIndices(MachineInstr *MI, unsigned &SrcOpIdx1,
                                      unsigned &SrcOpIdx2) const;
 
+  /// A pair composed of a register and a sub-register index.
+  /// Used to give some type checking when modeling Reg:SubReg.
+  struct RegSubRegPair {
+    unsigned Reg;
+    unsigned SubReg;
+    RegSubRegPair(unsigned Reg = 0, unsigned SubReg = 0)
+        : Reg(Reg), SubReg(SubReg) {}
+  };
+  /// A pair composed of a pair of a register and a sub-register index,
+  /// and another sub-register index.
+  /// Used to give some type checking when modeling Reg:SubReg1, SubReg2.
+  struct RegSubRegPairAndIdx : RegSubRegPair {
+    unsigned SubIdx;
+    RegSubRegPairAndIdx(unsigned Reg = 0, unsigned SubReg = 0,
+                        unsigned SubIdx = 0)
+        : RegSubRegPair(Reg, SubReg), SubIdx(SubIdx) {}
+  };
+
+  /// Build the equivalent inputs of a REG_SEQUENCE for the given \p MI
+  /// and \p DefIdx.
+  /// \p [out] InputRegs of the equivalent REG_SEQUENCE. Each element of
+  /// the list is modeled as <Reg:SubReg, SubIdx>.
+  /// E.g., REG_SEQUENCE vreg1:sub1, sub0, vreg2, sub1 would produce
+  /// two elements:
+  /// - vreg1:sub1, sub0
+  /// - vreg2<:0>, sub1
+  ///
+  /// \returns true if it is possible to build such an input sequence
+  /// with the pair \p MI, \p DefIdx. False otherwise.
+  ///
+  /// \pre MI.isRegSequence() or MI.isRegSequenceLike().
+  ///
+  /// \note The generic implementation does not provide any support for
+  /// MI.isRegSequenceLike(). In other words, one has to override
+  /// getRegSequenceLikeInputs for target specific instructions.
+  bool
+  getRegSequenceInputs(const MachineInstr &MI, unsigned DefIdx,
+                       SmallVectorImpl<RegSubRegPairAndIdx> &InputRegs) const;
+
   /// produceSameValue - Return true if two machine instructions would produce
   /// identical values. By default, this is only true when the two instructions
   /// are deemed identical except for defs. If this function is called when the
@@ -632,6 +671,20 @@ protected:
     return nullptr;
   }
 
+  /// \brief Target-dependent implementation of getRegSequenceInputs.
+  ///
+  /// \returns true if it is possible to build the equivalent
+  /// REG_SEQUENCE inputs with the pair \p MI, \p DefIdx. False otherwise.
+  ///
+  /// \pre MI.isRegSequenceLike().
+  ///
+  /// \see TargetInstrInfo::getRegSequenceInputs.
+  virtual bool getRegSequenceLikeInputs(
+      const MachineInstr &MI, unsigned DefIdx,
+      SmallVectorImpl<RegSubRegPairAndIdx> &InputRegs) const {
+    return false;
+  }
+
 public:
   /// canFoldMemoryOperand - Returns true for the specified load / store if
   /// folding is possible.

lib/CodeGen/TargetInstrInfo.cpp

@@ -852,3 +852,28 @@ computeOperandLatency(const InstrItineraryData *ItinData,
                           defaultDefLatency(ItinData->SchedModel, DefMI));
   return InstrLatency;
 }
+
+bool TargetInstrInfo::getRegSequenceInputs(
+    const MachineInstr &MI, unsigned DefIdx,
+    SmallVectorImpl<RegSubRegPairAndIdx> &InputRegs) const {
+  assert(MI.isRegSequence() ||
+         MI.isRegSequenceLike() && "Instruction do not have the proper type");
+
+  if (!MI.isRegSequence())
+    return getRegSequenceLikeInputs(MI, DefIdx, InputRegs);
+
+  // We are looking at:
+  // Def = REG_SEQUENCE v0, sub0, v1, sub1, ...
+  assert(DefIdx == 0 && "REG_SEQUENCE only has one def");
+  for (unsigned OpIdx = 1, EndOpIdx = MI.getNumOperands(); OpIdx != EndOpIdx;
+       OpIdx += 2) {
+    const MachineOperand &MOReg = MI.getOperand(OpIdx);
+    const MachineOperand &MOSubIdx = MI.getOperand(OpIdx + 1);
+    assert(MOSubIdx.isImm() &&
+           "One of the subindex of the reg_sequence is not an immediate");
+    // Record Reg:SubReg, SubIdx.
+    InputRegs.push_back(RegSubRegPairAndIdx(MOReg.getReg(), MOReg.getSubReg(),
+                                            (unsigned)MOSubIdx.getImm()));
+  }
+  return true;
+}

utils/TableGen/CodeGenInstruction.cpp

@@ -314,6 +314,7 @@ CodeGenInstruction::CodeGenInstruction(Record *R)
   hasPostISelHook = R->getValueAsBit("hasPostISelHook");
   hasCtrlDep   = R->getValueAsBit("hasCtrlDep");
   isNotDuplicable = R->getValueAsBit("isNotDuplicable");
+  isRegSequence = R->getValueAsBit("isRegSequence");
 
   bool Unset;
   mayLoad      = R->getValueAsBitOrUnset("mayLoad", Unset);

utils/TableGen/CodeGenInstruction.h

@@ -253,6 +253,7 @@ namespace llvm {
     bool hasExtraDefRegAllocReq : 1;
     bool isCodeGenOnly : 1;
     bool isPseudo : 1;
+    bool isRegSequence : 1;
 
     std::string DeprecatedReason;
     bool HasComplexDeprecationPredicate;

utils/TableGen/InstrInfoEmitter.cpp

@@ -505,6 +505,7 @@ void InstrInfoEmitter::emitRecord(const CodeGenInstruction &Inst, unsigned Num,
   if (Inst.isAsCheapAsAMove)   OS << "|(1<<MCID::CheapAsAMove)";
   if (Inst.hasExtraSrcRegAllocReq) OS << "|(1<<MCID::ExtraSrcRegAllocReq)";
   if (Inst.hasExtraDefRegAllocReq) OS << "|(1<<MCID::ExtraDefRegAllocReq)";
+  if (Inst.isRegSequence) OS << "|(1<<MCID::RegSequence)";
 
   // Emit all of the target-specific flags...
   BitsInit *TSF = Inst.TheDef->getValueAsBitsInit("TSFlags");