+
+namespace {
+ struct MSAH : public MachineFunctionPass {
+ static char ID;
+ MSAH() : MachineFunctionPass(&ID) {}
+
+ virtual bool runOnMachineFunction(MachineFunction &MF) {
+ const X86TargetMachine *TM =
+ static_cast<const X86TargetMachine *>(&MF.getTarget());
+ const X86RegisterInfo *X86RI = TM->getRegisterInfo();
+ MachineRegisterInfo &RI = MF.getRegInfo();
+ X86MachineFunctionInfo *FuncInfo = MF.getInfo<X86MachineFunctionInfo>();
+ unsigned StackAlignment = X86RI->getStackAlignment();
+
+ // Be over-conservative: scan over all vreg defs and find whether vector
+ // registers are used. If yes, there is a possibility that vector register
+ // will be spilled and thus require dynamic stack realignment.
+ for (unsigned RegNum = TargetRegisterInfo::FirstVirtualRegister;
+ RegNum < RI.getLastVirtReg(); ++RegNum)
+ if (RI.getRegClass(RegNum)->getAlignment() > StackAlignment) {
+ FuncInfo->setReserveFP(true);
+ return true;
+ }
+
+ // Nothing to do
+ return false;
+ }
+
+ virtual const char *getPassName() const {
+ return "X86 Maximal Stack Alignment Check";
+ }
+
+ virtual void getAnalysisUsage(AnalysisUsage &AU) const {
+ AU.setPreservesCFG();
+ MachineFunctionPass::getAnalysisUsage(AU);
+ }
+ };
+
+ char MSAH::ID = 0;
+}
+
+FunctionPass*
+llvm::createX86MaxStackAlignmentHeuristicPass() { return new MSAH(); }