Just set to 0

Author: JonPsson1

llvm/lib/Target/SystemZ/SystemZFrameLowering.cpp

@@ -66,6 +66,22 @@ SystemZFrameLowering::create(const SystemZSubtarget &STI) {
   return std::make_unique<SystemZELFFrameLowering>();
 }
 
+MachineBasicBlock::iterator SystemZFrameLowering::eliminateCallFramePseudoInstr(
+    MachineFunction &MF, MachineBasicBlock &MBB,
+    MachineBasicBlock::iterator MI) const {
+  switch (MI->getOpcode()) {
+  case SystemZ::ADJCALLSTACKDOWN:
+  case SystemZ::ADJCALLSTACKUP:
+    assert(hasReservedCallFrame(MF) &&
+           "ADJSTACKDOWN and ADJSTACKUP should be no-ops");
+    return MBB.erase(MI);
+    break;
+
+  default:
+    llvm_unreachable("Unexpected call frame instruction");
+  }
+}
+
 namespace {
 struct SZFrameSortingObj {
   bool IsValid = false;     // True if we care about this Object.

llvm/lib/Target/SystemZ/SystemZFrameLowering.h

@@ -41,6 +41,9 @@ class SystemZFrameLowering : public TargetFrameLowering {
   }
 
   bool hasReservedCallFrame(const MachineFunction &MF) const override;
+  MachineBasicBlock::iterator
+  eliminateCallFramePseudoInstr(MachineFunction &MF, MachineBasicBlock &MBB,
+                                MachineBasicBlock::iterator MI) const override;
 };
 
 class SystemZELFFrameLowering : public SystemZFrameLowering {

llvm/lib/Target/SystemZ/SystemZISelLowering.cpp

@@ -8107,16 +8107,18 @@ SystemZTargetLowering::emitAdjCallStack(MachineInstr &MI,
                                         MachineBasicBlock *BB) const {
   // Do the work of MachineFrameInfo::computeMaxCallFrameSize() early and
   // remove these nodes. Given that these nodes start out as a glued sequence
-  // it seems best to remove them here after instruction selection and
+  // it seems best to handle them here after instruction selection and
   // scheduling.
   MachineFrameInfo &MFI = BB->getParent()->getFrameInfo();
   uint32_t NumBytes = MI.getOperand(0).getImm();
   if (NumBytes > MFI.getMaxCallFrameSize())
     MFI.setMaxCallFrameSize(NumBytes);
   MFI.setAdjustsStack(true);
 
-  // TODO: MI should be erased. For now, keep it around as it seems to help
-  // scheduling around calls slightly in general (fix MachineScheduler).
+  // Set the NumBytes value to 0 to avoid problems of maintaining the call
+  // frame size across CFG edges.  TODO: MI could be erased, but it seems to
+  // help scheduling around calls slightly (fix MachineScheduler + handle the
+  // adjustsStack implication).
   MI.getOperand(0).setImm(0);
 
   return BB;

llvm/lib/Target/SystemZ/SystemZInstrInfo.cpp

@@ -59,7 +59,7 @@ static uint64_t allOnes(unsigned int Count) {
 void SystemZInstrInfo::anchor() {}
 
 SystemZInstrInfo::SystemZInstrInfo(SystemZSubtarget &sti)
-    : SystemZGenInstrInfo(-1, -1),
+    : SystemZGenInstrInfo(SystemZ::ADJCALLSTACKDOWN, SystemZ::ADJCALLSTACKUP),
       RI(sti.getSpecialRegisters()->getReturnFunctionAddressRegister()),
       STI(sti) {}
 
@@ -1513,11 +1513,6 @@ bool SystemZInstrInfo::expandPostRAPseudo(MachineInstr &MI) const {
     expandLoadStackGuard(&MI);
     return true;
 
-  case SystemZ::ADJCALLSTACKDOWN:
-  case SystemZ::ADJCALLSTACKUP:
-    MI.eraseFromParent();
-    return true;
-
   default:
     return false;
   }