[llvm] [AMDGPU] Support block load/store for CSR (PR #130013)

[Matt Arsenault via llvm-commits]

================
@@ -1763,6 +1863,110 @@ bool SIFrameLowering::allocateScavengingFrameIndexesNearIncomingSP(
   return true;
 }
 
+bool SIFrameLowering::spillCalleeSavedRegisters(
+    MachineBasicBlock &MBB, MachineBasicBlock::iterator MI,
+    ArrayRef<CalleeSavedInfo> CSI, const TargetRegisterInfo *TRI) const {
+  MachineFunction *MF = MBB.getParent();
+  const GCNSubtarget &ST = MF->getSubtarget<GCNSubtarget>();
+  if (!ST.useVGPRBlockOpsForCSR())
+    return false;
+
+  MachineFrameInfo &FrameInfo = MF->getFrameInfo();
+  SIMachineFunctionInfo *MFI = MF->getInfo<SIMachineFunctionInfo>();
+  const SIInstrInfo *TII = ST.getInstrInfo();
+  SIMachineFunctionInfo *FuncInfo = MF->getInfo<SIMachineFunctionInfo>();
+
+  const TargetRegisterClass *BlockRegClass =
+      static_cast<const SIRegisterInfo *>(TRI)->getRegClassForBlockOp(*MF);
+  for (const CalleeSavedInfo &CS : CSI) {
+    Register Reg = CS.getReg();
+    if (!BlockRegClass->contains(Reg) ||
+        !FuncInfo->hasMaskForVGPRBlockOps(Reg)) {
+      spillCalleeSavedRegister(MBB, MI, CS, TII, TRI);
+      continue;
+    }
+
+    // Build a scratch block store.
+    uint32_t Mask = FuncInfo->getMaskForVGPRBlockOps(Reg);
+    int FrameIndex = CS.getFrameIdx();
+    MachinePointerInfo PtrInfo =
+        MachinePointerInfo::getFixedStack(*MF, FrameIndex);
+    MachineMemOperand *MMO =
+        MF->getMachineMemOperand(PtrInfo, MachineMemOperand::MOStore,
+                                 FrameInfo.getObjectSize(FrameIndex),
+                                 FrameInfo.getObjectAlign(FrameIndex));
+
+    BuildMI(MBB, MI, MI->getDebugLoc(),
+            TII->get(AMDGPU::SI_BLOCK_SPILL_V1024_SAVE))
+        .addReg(Reg, getKillRegState(false))
+        .addFrameIndex(FrameIndex)
+        .addReg(MFI->getStackPtrOffsetReg())
+        .addImm(0)
+        .addImm(Mask)
+        .addMemOperand(MMO);
+
+    FuncInfo->setHasSpilledVGPRs();
+
+    // Add the register to the liveins. This is necessary because if any of the
+    // VGPRs in the register block is reserved (e.g. if it's a WWM register),
+    // then the whole block will be marked as reserved and `updateLiveness` will
+    // skip it.
+    MBB.addLiveIn(Reg);
----------------
arsenm wrote:

does this need sortAndUniqueLiveIns somewhere, or does it happen to get caught by the restore case 

https://github.com/llvm/llvm-project/pull/130013