[ARM] Mark VSETLNi32 with the InsertSubreg property and implement the related

target hook.

This patch teaches the compiler that:
dX = VSETLNi32 dY, rZ, imm
is the same as:
dX = INSERT_SUBREG dY, rZ, translateImmToSubIdx(imm)

<rdar://problem/12702965>


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@216143 91177308-0d34-0410-b5e6-96231b3b80d8

lib/Target/ARM/ARMInstrInfo.cpp

@@ -144,6 +144,29 @@ bool ARMInstrInfo::getExtractSubregLikeInputs(
   llvm_unreachable("Target dependent opcode missing");
 }
 
+bool ARMInstrInfo::getInsertSubregLikeInputs(
+    const MachineInstr &MI, unsigned DefIdx, RegSubRegPair &BaseReg,
+    RegSubRegPairAndIdx &InsertedReg) const {
+  assert(DefIdx < MI.getDesc().getNumDefs() && "Invalid definition index");
+  assert(MI.isInsertSubregLike() && "Invalid kind of instruction");
+
+  switch (MI.getOpcode()) {
+  case ARM::VSETLNi32:
+    // dX = VSETLNi32 dY, rZ, imm
+    const MachineOperand &MOBaseReg = MI.getOperand(1);
+    const MachineOperand &MOInsertedReg = MI.getOperand(2);
+    const MachineOperand &MOIndex = MI.getOperand(3);
+    BaseReg.Reg = MOBaseReg.getReg();
+    BaseReg.SubReg = MOBaseReg.getSubReg();
+
+    InsertedReg.Reg = MOInsertedReg.getReg();
+    InsertedReg.SubReg = MOInsertedReg.getSubReg();
+    InsertedReg.SubIdx = MOIndex.getImm() == 0 ? ARM::ssub_0 : ARM::ssub_1;
+    return true;
+  }
+  llvm_unreachable("Target dependent opcode missing");
+}
+
 namespace {
   /// ARMCGBR - Create Global Base Reg pass. This initializes the PIC
   /// global base register for ARM ELF.

lib/Target/ARM/ARMInstrInfo.h

@@ -68,6 +68,23 @@ public:
   bool getExtractSubregLikeInputs(const MachineInstr &MI, unsigned DefIdx,
                                   RegSubRegPairAndIdx &InputReg) const override;
 
+  /// Build the equivalent inputs of a INSERT_SUBREG for the given \p MI
+  /// and \p DefIdx.
+  /// \p [out] BaseReg and \p [out] InsertedReg contain
+  /// the equivalent inputs of INSERT_SUBREG.
+  /// E.g., INSERT_SUBREG vreg0:sub0, vreg1:sub1, sub3 would produce:
+  /// - BaseReg: vreg0:sub0
+  /// - InsertedReg: vreg1:sub1, sub3
+  ///
+  /// \returns true if it is possible to build such an input sequence
+  /// with the pair \p MI, \p DefIdx. False otherwise.
+  ///
+  /// \pre MI.isInsertSubregLike().
+  bool
+  getInsertSubregLikeInputs(const MachineInstr &MI, unsigned DefIdx,
+                            RegSubRegPair &BaseReg,
+                            RegSubRegPairAndIdx &InsertedReg) const override;
+
 private:
   void expandLoadStackGuard(MachineBasicBlock::iterator MI,
                             Reloc::Model RM) const override;

lib/Target/ARM/ARMInstrNEON.td

@@ -5499,6 +5499,9 @@ def VSETLNi32 : NVSetLane<{1,1,1,0,0,0,?,0}, 0b1011, 0b00, (outs DPR:$V),
                           [(set DPR:$V, (insertelt (v2i32 DPR:$src1),
                                            GPR:$R, imm:$lane))]> {
   let Inst{21} = lane{0};
+  // This instruction is equivalent as
+  // $V = INSERT_SUBREG $src1, $R, translateImmToSubIdx($imm)
+  let isInsertSubreg = 1;
 }
 }
 def : Pat<(vector_insert (v16i8 QPR:$src1), GPR:$src2, imm:$lane),