Revert 86b1b06 "MachineVerifier: Check stack protector is top-most in frame" (#122444)

Reverts #121481

This is causing build failures on EXPENSIVE_CHECKS builds:
https://lab.llvm.org/buildbot/#/builders/187/builds/3653
https://lab.llvm.org/buildbot/#/builders/16/builds/11758

Author: RKSimon

llvm/lib/CodeGen/MachineVerifier.cpp

@@ -353,8 +353,6 @@ struct MachineVerifier {
                        LaneBitmask LaneMask = LaneBitmask::getNone());
 
   void verifyStackFrame();
-  // Check that the stack protector is the top-most object in the stack.
-  void verifyStackProtector();
 
   void verifySlotIndexes() const;
   void verifyProperties(const MachineFunction &MF);
@@ -711,10 +709,8 @@ void MachineVerifier::visitMachineFunctionBefore() {
   // Check that the register use lists are sane.
   MRI->verifyUseLists();
 
-  if (!MF->empty()) {
+  if (!MF->empty())
     verifyStackFrame();
-    verifyStackProtector();
-  }
 }
 
 void
@@ -4042,49 +4038,3 @@ void MachineVerifier::verifyStackFrame() {
     }
   }
 }
-
-void MachineVerifier::verifyStackProtector() {
-  const MachineFrameInfo &MFI = MF->getFrameInfo();
-  if (!MFI.hasStackProtectorIndex())
-    return;
-  // Only applicable when the offsets of frame objects have been determined,
-  // which is indicated by a non-zero stack size.
-  if (!MFI.getStackSize())
-    return;
-  const TargetFrameLowering &TFI = *MF->getSubtarget().getFrameLowering();
-  bool StackGrowsDown =
-      TFI.getStackGrowthDirection() == TargetFrameLowering::StackGrowsDown;
-  // Collect the frame indices of the callee-saved registers which are spilled
-  // to the stack. These are the registers that are stored above the stack
-  // protector.
-  SmallSet<unsigned, 4> CalleeSavedFrameIndices;
-  if (MFI.isCalleeSavedInfoValid()) {
-    for (const CalleeSavedInfo &Info : MFI.getCalleeSavedInfo()) {
-      if (!Info.isSpilledToReg())
-        CalleeSavedFrameIndices.insert(Info.getFrameIdx());
-    }
-  }
-  unsigned FI = MFI.getStackProtectorIndex();
-  int64_t SPStart = MFI.getObjectOffset(FI);
-  int64_t SPEnd = SPStart + MFI.getObjectSize(FI);
-  for (unsigned I = 0, E = MFI.getObjectIndexEnd(); I != E; ++I) {
-    if (I == FI)
-      continue;
-    // Variable-sized objects do not have a fixed offset.
-    if (MFI.isVariableSizedObjectIndex(I))
-      continue;
-    if (CalleeSavedFrameIndices.contains(I))
-      continue;
-    int64_t ObjStart = MFI.getObjectOffset(I);
-    int64_t ObjEnd = ObjStart + MFI.getObjectSize(I);
-    if (SPStart < ObjEnd && ObjStart < SPEnd) {
-      report("Stack protector overlaps with another stack object", MF);
-      break;
-    }
-    if ((StackGrowsDown && SPStart <= ObjStart) ||
-        (!StackGrowsDown && SPStart >= ObjStart)) {
-      report("Stack protector is not the top-most object on the stack", MF);
-      break;
-    }
-  }
-}