Freeze reserved registers before starting register allocation.

The register allocators don't currently support adding reserved
registers while they are running.  Extend the MRI API to keep track of
the set of reserved registers when register allocation started.

Target hooks like hasFP() and needsStackRealignment() can look at this
set to avoid reserving more registers during register allocation.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@147577 91177308-0d34-0410-b5e6-96231b3b80d8

lib/CodeGen/MachineRegisterInfo.cpp

@@ -259,3 +259,7 @@ void MachineRegisterInfo::dumpUses(unsigned Reg) const {
     I.getOperand().getParent()->dump();
 }
 #endif
+
+void MachineRegisterInfo::freezeReservedRegs(const MachineFunction &MF) {
+  ReservedRegs = TRI->getReservedRegs(MF);
+}

lib/CodeGen/RegAllocBasic.cpp

@@ -233,6 +233,7 @@ void RegAllocBase::init(VirtRegMap &vrm, LiveIntervals &lis) {
   MRI = &vrm.getRegInfo();
   VRM = &vrm;
   LIS = &lis;
+  MRI->freezeReservedRegs(vrm.getMachineFunction());
   RegClassInfo.runOnMachineFunction(vrm.getMachineFunction());
 
   const unsigned NumRegs = TRI->getNumRegs();

lib/CodeGen/RegAllocFast.cpp

@@ -1047,6 +1047,7 @@ bool RAFast::runOnMachineFunction(MachineFunction &Fn) {
   TM = &Fn.getTarget();
   TRI = TM->getRegisterInfo();
   TII = TM->getInstrInfo();
+  MRI->freezeReservedRegs(Fn);
   RegClassInfo.runOnMachineFunction(Fn);
   UsedInInstr.resize(TRI->getNumRegs());
 

lib/CodeGen/RegAllocPBQP.cpp

@@ -619,6 +619,7 @@ bool RegAllocPBQP::runOnMachineFunction(MachineFunction &MF) {
   vrm = &getAnalysis<VirtRegMap>();
   spiller.reset(createInlineSpiller(*this, MF, *vrm));
 
+  mri->freezeReservedRegs(MF);
 
   DEBUG(dbgs() << "PBQP Register Allocating for " << mf->getFunction()->getName() << "\n");