+/// X86SelectRet - Select and emit code to implement ret instructions.
+bool X86FastISel::X86SelectRet(const Instruction *I) {
+ const ReturnInst *Ret = cast<ReturnInst>(I);
+ const Function &F = *I->getParent()->getParent();
+
+ if (!FuncInfo.CanLowerReturn)
+ return false;
+
+ CallingConv::ID CC = F.getCallingConv();
+ if (CC != CallingConv::C &&
+ CC != CallingConv::Fast &&
+ CC != CallingConv::X86_FastCall)
+ return false;
+
+ if (Subtarget->isTargetWin64())
+ return false;
+
+ // Don't handle popping bytes on return for now.
+ if (FuncInfo.MF->getInfo<X86MachineFunctionInfo>()
+ ->getBytesToPopOnReturn() != 0)
+ return 0;
+
+ // fastcc with -tailcallopt is intended to provide a guaranteed
+ // tail call optimization. Fastisel doesn't know how to do that.
+ if (CC == CallingConv::Fast && GuaranteedTailCallOpt)
+ return false;
+
+ // Let SDISel handle vararg functions.
+ if (F.isVarArg())
+ return false;
+
+ if (Ret->getNumOperands() > 0) {
+ SmallVector<ISD::OutputArg, 4> Outs;
+ GetReturnInfo(F.getReturnType(), F.getAttributes().getRetAttributes(),
+ Outs, TLI);
+
+ // Analyze operands of the call, assigning locations to each operand.
+ SmallVector<CCValAssign, 16> ValLocs;
+ CCState CCInfo(CC, F.isVarArg(), TM, ValLocs, I->getContext());
+ CCInfo.AnalyzeReturn(Outs, RetCC_X86);
+
+ const Value *RV = Ret->getOperand(0);
+ unsigned Reg = getRegForValue(RV);
+ if (Reg == 0)
+ return false;
+
+ // Only handle a single return value for now.
+ if (ValLocs.size() != 1)
+ return false;
+
+ CCValAssign &VA = ValLocs[0];
+
+ // Don't bother handling odd stuff for now.
+ if (VA.getLocInfo() != CCValAssign::Full)
+ return false;
+ // Only handle register returns for now.
+ if (!VA.isRegLoc())
+ return false;
+ // TODO: For now, don't try to handle cases where getLocInfo()
+ // says Full but the types don't match.
+ if (TLI.getValueType(RV->getType()) != VA.getValVT())
+ return false;
+
+ // The calling-convention tables for x87 returns don't tell
+ // the whole story.
+ if (VA.getLocReg() == X86::ST0 || VA.getLocReg() == X86::ST1)
+ return false;
+
+ // Make the copy.
+ unsigned SrcReg = Reg + VA.getValNo();
+ unsigned DstReg = VA.getLocReg();
+ const TargetRegisterClass* SrcRC = MRI.getRegClass(SrcReg);
+ // Avoid a cross-class copy. This is very unlikely.
+ if (!SrcRC->contains(DstReg))
+ return false;
+ BuildMI(*FuncInfo.MBB, FuncInfo.InsertPt, DL, TII.get(TargetOpcode::COPY),
+ DstReg).addReg(SrcReg);
+
+ // Mark the register as live out of the function.
+ MRI.addLiveOut(VA.getLocReg());
+ }
+
+ // Now emit the RET.
+ BuildMI(*FuncInfo.MBB, FuncInfo.InsertPt, DL, TII.get(X86::RET));
+ return true;
+}
+