[X86] Remove side-effects from determineCalleeSaves

[thegameg]

Summary

It should be possible for one to call (Target)FrameLowering::determineCalleeSaves multiple times. I don't think it should have side-effects as creating stack objects and setting global MachineFunctionInfo state as it is doing today (in other back-ends as well).

This moves the creation of stack objects from determineCalleeSaves to assignCalleeSavedSpillSlots in the X86 back-end.

[rnk]

lgtm, thanks!

lib/Target/X86/X86FrameLowering.cpp

bool X86FrameLowering::assignCalleeSavedSpillSlots(
     MachineFunction &MF, const TargetRegisterInfo *TRI,
     std::vector<CalleeSavedInfo> &CSI) const {
   MachineFrameInfo &MFI = MF.getFrameInfo();
   X86MachineFunctionInfo *X86FI = MF.getInfo<X86MachineFunctionInfo>();
 
   unsigned CalleeSavedFrameSize = 0;
   int SpillSlotOffset = getOffsetOfLocalArea() + X86FI->getTCReturnAddrDelta();
 
+  int64_t TailCallReturnAddrDelta = X86FI->getTCReturnAddrDelta();
+
+  if (TailCallReturnAddrDelta < 0) {
+    // create RETURNADDR area
+    //   arg
+    //   arg
+    //   RETADDR
+    //   { ...
+    //     RETADDR area
+    //     ...
+    //   }
+    //   [EBP]
+    MFI.CreateFixedObject(-TailCallReturnAddrDelta,
+                           TailCallReturnAddrDelta - SlotSize, true);
+  }
+
+  // Spill the BasePtr if it's used.
+  if (this->TRI->hasBasePointer(MF)) {
+    // Allocate a spill slot for EBP if we have a base pointer and EH funclets.
+    if (MF.hasEHFunclets()) {
+      int FI = MFI.CreateSpillStackObject(SlotSize, SlotSize);
+      X86FI->setHasSEHFramePtrSave(true);
+      X86FI->setSEHFramePtrSaveIndex(FI);
+    }
+  }
+
   if (hasFP(MF)) {
     // emitPrologue always spills frame register the first thing.
     SpillSlotOffset -= SlotSize;
     MFI.CreateFixedSpillStackObject(SlotSize, SpillSlotOffset);
 
     // Since emitPrologue and emitEpilogue will handle spilling and restoring of
     // the frame register, we can delete it from CSI list and not have to worry
     // about avoiding it later.
bool X86FrameLowering::restoreCalleeSavedRegisters(MachineBasicBlock &MBB,
   return true;
 }
 
 void X86FrameLowering::determineCalleeSaves(MachineFunction &MF,
                                             BitVector &SavedRegs,
                                             RegScavenger *RS) const {
   TargetFrameLowering::determineCalleeSaves(MF, SavedRegs, RS);
 
-  MachineFrameInfo &MFI = MF.getFrameInfo();
-
-  X86MachineFunctionInfo *X86FI = MF.getInfo<X86MachineFunctionInfo>();
-  int64_t TailCallReturnAddrDelta = X86FI->getTCReturnAddrDelta();
-
-  if (TailCallReturnAddrDelta < 0) {
-    // create RETURNADDR area
-    //   arg
-    //   arg
-    //   RETADDR
-    //   { ...
-    //     RETADDR area
-    //     ...
-    //   }
-    //   [EBP]
-    MFI.CreateFixedObject(-TailCallReturnAddrDelta,
-                           TailCallReturnAddrDelta - SlotSize, true);
-  }
-
   // Spill the BasePtr if it's used.
-  if (TRI->hasBasePointer(MF)) {
+  if (TRI->hasBasePointer(MF))
     SavedRegs.set(TRI->getBaseRegister());
-
-    // Allocate a spill slot for EBP if we have a base pointer and EH funclets.
-    if (MF.hasEHFunclets()) {
-      int FI = MFI.CreateSpillStackObject(SlotSize, SlotSize);
-      X86FI->setHasSEHFramePtrSave(true);
-      X86FI->setSEHFramePtrSaveIndex(FI);
-    }
-  }
 }
 
 static bool
 HasNestArgument(const MachineFunction *MF) {
   const Function &F = MF->getFunction();
   for (Function::const_arg_iterator I = F.arg_begin(), E = F.arg_end();
        I != E; I++) {
     if (I->hasNestAttr())