[X86] Remove mergeSPUpdatesUp()

[mkuper]

Summary

X86FrameLowering has both a mergeSPUpdates() that accepts a direction, and an mergeSPUpdatesUp(), which seem to do the same thing, except for a slightly different interface.
NFC.

Review is mostly for sanity - I don't understand why both functions existed in the first place.

[rnk]

lgtm

Wow, this code duplication dates back to r42870 / 2007. Originally it was split into merge*Up / merge*Down, and then Arnold made a combined version without deleting the specialized variants.

llvm/trunk/lib/Target/X86/X86FrameLowering.cpp

if (UseLEA) {
     MI = BuildMI(MBB, MBBI, DL, TII.get(Opc), StackPtr)
              .addReg(StackPtr)
              .addImm(AbsOffset);
     MI->getOperand(3).setIsDead(); // The EFLAGS implicit def is dead.
   }
   return MI;
 }
 
-/// mergeSPUpdatesUp - Merge two stack-manipulating instructions upper iterator.
-static
-void mergeSPUpdatesUp(MachineBasicBlock &MBB, MachineBasicBlock::iterator &MBBI,
-                      unsigned StackPtr, uint64_t *NumBytes = nullptr) {
-  if (MBBI == MBB.begin()) return;
-
-  MachineBasicBlock::iterator PI = std::prev(MBBI);
-  unsigned Opc = PI->getOpcode();
-  if ((Opc == X86::ADD64ri32 || Opc == X86::ADD64ri8 ||
-       Opc == X86::ADD32ri || Opc == X86::ADD32ri8 ||
-       Opc == X86::LEA32r || Opc == X86::LEA64_32r) &&
-      PI->getOperand(0).getReg() == StackPtr) {
-    if (NumBytes)
-      *NumBytes += PI->getOperand(2).getImm();
-    MBB.erase(PI);
-  } else if ((Opc == X86::SUB64ri32 || Opc == X86::SUB64ri8 ||
-              Opc == X86::SUB32ri || Opc == X86::SUB32ri8) &&
-             PI->getOperand(0).getReg() == StackPtr) {
-    if (NumBytes)
-      *NumBytes -= PI->getOperand(2).getImm();
-    MBB.erase(PI);
-  }
-}
-
 int X86FrameLowering::mergeSPUpdates(MachineBasicBlock &MBB,
                                      MachineBasicBlock::iterator &MBBI,
                                      bool doMergeWithPrevious) const {
   if ((doMergeWithPrevious && MBBI == MBB.begin()) ||
       (!doMergeWithPrevious && MBBI == MBB.end()))
     return 0;
 
   MachineBasicBlock::iterator PI = doMergeWithPrevious ? std::prev(MBBI) : MBBI;
void X86FrameLowering::emitEpilogue(MachineFunction &MF,
   MachineBasicBlock::iterator FirstCSPop = MBBI;
 
   if (MBBI != MBB.end())
     DL = MBBI->getDebugLoc();
 
   // If there is an ADD32ri or SUB32ri of ESP immediately before this
   // instruction, merge the two instructions.
   if (NumBytes || MFI->hasVarSizedObjects())
-    mergeSPUpdatesUp(MBB, MBBI, StackPtr, &NumBytes);
+    NumBytes += mergeSPUpdates(MBB, MBBI, true);
 
   // If dynamic alloca is used, then reset esp to point to the last callee-saved
   // slot before popping them off! Same applies for the case, when stack was
   // realigned.
   if (TRI->needsStackRealignment(MF) || MFI->hasVarSizedObjects()) {
     if (TRI->needsStackRealignment(MF))
       MBBI = FirstCSPop;
     unsigned SEHFrameOffset = calculateSetFPREG(SEHStackAllocAmt);