[llvm] [ARM] Specifically delineate between different GPRCS2 positions (PR #116716)

[Benson Chu via llvm-commits]

================
@@ -1063,33 +1068,34 @@ void ARMFrameLowering::emitPrologue(MachineFunction &MF,
     }
   }
 
-  // Move past DPRCS1.
-  if (DPRCSSize > 0) {
+  // Move past DPRCS1Size.
+  if (DPRCS1Size > 0) {
     // Since vpush register list cannot have gaps, there may be multiple vpush
     // instructions in the prologue.
     while (MBBI != MBB.end() && MBBI->getOpcode() == ARM::VSTMDDB_UPD) {
       DefCFAOffsetCandidates.addInst(MBBI, sizeOfSPAdjustment(*MBBI),
                                      BeforeFPPush);
-      LastPush = MBBI++;
+      DPRCS1Push = LastPush = MBBI++;
     }
   }
 
   // Move past the aligned DPRCS2 area.
-  if (AFI->getNumAlignedDPRCS2Regs() > 0) {
+  if (DPRCS2Size > 0) {
     MBBI = skipAlignedDPRCS2Spills(MBBI, AFI->getNumAlignedDPRCS2Regs());
     // The code inserted by emitAlignedDPRCS2Spills realigns the stack, and
     // leaves the stack pointer pointing to the DPRCS2 area.
     //
     // Adjust NumBytes to represent the stack slots below the DPRCS2 area.
     NumBytes += MFI.getObjectOffset(D8SpillFI);
   } else
-    NumBytes = DPRCSOffset;
-
-  // Move GPRCS2, if using using SplitR11WindowsSEH.
-  if (GPRCS2Size > 0 && PushPopSplit == ARMSubtarget::SplitR11WindowsSEH) {
-    GPRCS2Push = LastPush = MBBI++;
-    DefCFAOffsetCandidates.addInst(LastPush, GPRCS2Size, BeforeFPPush);
-    if (FramePtrSpillArea == SpillArea::GPRCS2)
+    NumBytes = DPRCS1Offset;
+
+  // Move GPRCS3, if using using SplitR11WindowsSEH.
+  if (GPRCS3Size > 0) {
+    assert(PushPopSplit == ARMSubtarget::SplitR11WindowsSEH);
----------------
pestctrl wrote:

I left these asserts here to serve as reminders of what `GPRCS2Size > 0` and `GPRCS3Size > 0` likewise imply, but someone doesn't like them being here, I can remove them. Checking for GPRCS2Size/GPRCS3Size provides all the frame code needs to know. 

https://github.com/llvm/llvm-project/pull/116716