1 files changed, 84 insertions, 0 deletions
diff --git a/llvm/lib/Target/X86/X86InstructionSelector.cpp b/llvm/lib/Target/X86/X86InstructionSelector.cpp
index 0750f272799..4996288a193 100644
--- a/llvm/lib/Target/X86/X86InstructionSelector.cpp
+++ b/llvm/lib/Target/X86/X86InstructionSelector.cpp
@@ -114,6 +114,8 @@ private:
   bool selectImplicitDefOrPHI(MachineInstr &I, MachineRegisterInfo &MRI) const;
   bool selectShift(MachineInstr &I, MachineRegisterInfo &MRI,
                    MachineFunction &MF) const;
+  bool selectSDiv(MachineInstr &I, MachineRegisterInfo &MRI,
+                   MachineFunction &MF) const;
 
   // emit insert subreg instruction and insert it before MachineInstr &I
   bool emitInsertSubreg(unsigned DstReg, unsigned SrcReg, MachineInstr &I,
@@ -379,6 +381,8 @@ bool X86InstructionSelector::select(MachineInstr &I,
   case TargetOpcode::G_ASHR:
   case TargetOpcode::G_LSHR:
     return selectShift(I, MRI, MF);
+  case TargetOpcode::G_SDIV:
+    return selectSDiv(I, MRI, MF);
   }
 
   return false;
@@ -1481,6 +1485,86 @@ bool X86InstructionSelector::selectShift(MachineInstr &I,
   return true;
 }
 
+bool X86InstructionSelector::selectSDiv(MachineInstr &I,
+                                        MachineRegisterInfo &MRI,
+                                        MachineFunction &MF) const {
+
+  assert(I.getOpcode() == TargetOpcode::G_SDIV && "unexpected instruction");
+
+  const unsigned DstReg = I.getOperand(0).getReg();
+  const unsigned DividentReg = I.getOperand(1).getReg();
+  const unsigned DiviserReg = I.getOperand(2).getReg();
+
+  const LLT RegTy = MRI.getType(DstReg);
+  assert(RegTy == MRI.getType(DividentReg) &&
+         RegTy == MRI.getType(DiviserReg) &&
+         "Arguments and return value types must match");
+
+  const RegisterBank &RegRB = *RBI.getRegBank(DstReg, MRI, TRI);
+
+  // For the X86 IDIV instruction, in most cases the dividend
+  // (numerator) must be in a specific register pair highreg:lowreg,
+  // producing the quotient in lowreg and the remainder in highreg.
+  // For most data types, to set up the instruction, the dividend is
+  // copied into lowreg, and lowreg is sign-extended into highreg.  The
+  // exception is i8, where the dividend is defined as a single register rather
+  // than a register pair, and we therefore directly sign-extend the dividend
+  // into lowreg, instead of copying, and ignore the highreg.
+  const static struct SDivEntry {
+    unsigned SizeInBits;
+    unsigned QuotientReg;
+    unsigned DividentRegUpper;
+    unsigned DividentRegLower;
+    unsigned OpSignExtend;
+    unsigned OpCopy;
+    unsigned OpDiv;
+  } OpTable[] = {
+      {8, X86::AL, X86::NoRegister, X86::AX, 0, X86::MOVSX16rr8,
+       X86::IDIV8r}, // i8
+      {16, X86::AX, X86::DX, X86::AX, X86::CWD, TargetOpcode::COPY,
+       X86::IDIV16r}, // i16
+      {32, X86::EAX, X86::EDX, X86::EAX, X86::CDQ, TargetOpcode::COPY,
+       X86::IDIV32r}, // i32
+      {64, X86::RAX, X86::RDX, X86::RAX, X86::CQO, TargetOpcode::COPY,
+       X86::IDIV64r} // i64
+  };
+
+  if (RegRB.getID() != X86::GPRRegBankID)
+    return false;
+
+  auto SDivEntryIt = std::find_if(
+      std::begin(OpTable), std::end(OpTable), [RegTy](const SDivEntry &El) {
+    return El.SizeInBits == RegTy.getSizeInBits();
+      });
+
+  if (SDivEntryIt == std::end(OpTable))
+    return false;
+
+  const TargetRegisterClass *RegRC = getRegClass(RegTy, RegRB);
+  if (!RBI.constrainGenericRegister(DividentReg, *RegRC, MRI) ||
+      !RBI.constrainGenericRegister(DiviserReg, *RegRC, MRI) ||
+      !RBI.constrainGenericRegister(DstReg, *RegRC, MRI)) {
+    DEBUG(dbgs() << "Failed to constrain " << TII.getName(I.getOpcode())
+                 << " operand\n");
+    return false;
+  }
+
+  BuildMI(*I.getParent(), I, I.getDebugLoc(), TII.get(SDivEntryIt->OpCopy),
+          SDivEntryIt->DividentRegLower)
+      .addReg(DividentReg);
+  if (SDivEntryIt->DividentRegUpper != X86::NoRegister)
+    BuildMI(*I.getParent(), I, I.getDebugLoc(),
+            TII.get(SDivEntryIt->OpSignExtend));
+  BuildMI(*I.getParent(), I, I.getDebugLoc(), TII.get(SDivEntryIt->OpDiv))
+      .addReg(DiviserReg);
+  BuildMI(*I.getParent(), I, I.getDebugLoc(), TII.get(TargetOpcode::COPY),
+          DstReg)
+      .addReg(SDivEntryIt->QuotientReg);
+
+  I.eraseFromParent();
+  return true;
+}
+
 InstructionSelector *
 llvm::createX86InstructionSelector(const X86TargetMachine &TM,
                                    X86Subtarget &Subtarget,