allSGPRSpillsAreDead() should use actual FP/BP frame indices

The SGPR spills happen in SILowerSGPRSpills() and allSGPRSpillsAreDead()
make sure there are no SGPR spills pending during PEI. But the FP/BP
spills happen during PEI and are exceptions.

Use actual frame indices of FP/BP in allSGPRSpillsAreDead() to
accommodate the exceptions.

Differential Revision: https://reviews.llvm.org/D86291

Author: RamNalamothu

llvm/lib/Target/AMDGPU/SIFrameLowering.cpp

@@ -1076,15 +1076,15 @@ static bool allStackObjectsAreDead(const MachineFrameInfo &MFI) {
 }
 
 #ifndef NDEBUG
-static bool allSGPRSpillsAreDead(const MachineFrameInfo &MFI,
-                                 Optional<int> FramePointerSaveIndex,
-                                 Optional<int> BasePointerSaveIndex) {
+static bool allSGPRSpillsAreDead(const MachineFunction &MF) {
+  const MachineFrameInfo &MFI = MF.getFrameInfo();
+  const SIMachineFunctionInfo *FuncInfo = MF.getInfo<SIMachineFunctionInfo>();
   for (int I = MFI.getObjectIndexBegin(), E = MFI.getObjectIndexEnd();
        I != E; ++I) {
     if (!MFI.isDeadObjectIndex(I) &&
         MFI.getStackID(I) == TargetStackID::SGPRSpill &&
-        ((FramePointerSaveIndex && I != FramePointerSaveIndex) ||
-         (BasePointerSaveIndex && I != BasePointerSaveIndex))) {
+        (I != FuncInfo->FramePointerSaveIndex &&
+         I != FuncInfo->BasePointerSaveIndex)) {
       return false;
     }
   }
@@ -1111,7 +1111,7 @@ void SIFrameLowering::processFunctionBeforeFrameFinalized(
   SIMachineFunctionInfo *FuncInfo = MF.getInfo<SIMachineFunctionInfo>();
 
   FuncInfo->removeDeadFrameIndices(MFI);
-  assert(allSGPRSpillsAreDead(MFI, None, None) &&
+  assert(allSGPRSpillsAreDead(MF) &&
          "SGPR spill should have been removed in SILowerSGPRSpills");
 
   // FIXME: The other checks should be redundant with allStackObjectsAreDead,