MIR Statepoint refactoring: pass GC pointers in VRegs. Part 2/5.

[dantrushin]

Summary

Change MIR representation of STATEPOINT instruction from explicit
spill/reload of GC pointer arguments around statepoint to simply
assigning them to virtual registers. Then they can be spilled as
necessary. Relocated pointers are represented as STATEPOINT's Def
operands (tied to corresponding derived pointers from GC args list):

rel1,rel2,... = STATEPOINT ..., derived1<tied-def0>, derived2<tied-def1>, ...

This patch adds necessary modifications for utility classes -
StatepointOpers and MachineVerifier to correctly handle statepoints
with possible Def operands.

Depends On: D80191

[dantrushin]

Abandoned in favor of D81645

llvm/include/llvm/CodeGen/StackMaps.h

class StatepointOpers {
   // instruction.
   enum { IDPos, NBytesPos, NCallArgsPos, CallTargetPos, MetaEnd };
 
   // These values are relative offsets from the start of the statepoint meta
   // arguments (i.e. the end of the call arguments).
   enum { CCOffset = 1, FlagsOffset = 3, NumDeoptOperandsOffset = 5 };
 
 public:
-  explicit StatepointOpers(const MachineInstr *MI) : MI(MI) {}
+  explicit StatepointOpers(const MachineInstr *MI) : MI(MI) {
+    NumDefs = MI->getNumDefs();
+  }
 
   /// Get index of statepoint ID operand.
-  unsigned getIDPos() const { return IDPos; }
+  unsigned getIDPos() const { return NumDefs + IDPos; }
 
   /// Get index of Num Patch Bytes operand.
-  unsigned getNBytesPos() const { return NBytesPos; }
+  unsigned getNBytesPos() const { return NumDefs + NBytesPos; }
 
   /// Get index of Num Call Arguments operand.
-  unsigned getNCallArgsPos() const { return NCallArgsPos; }
+  unsigned getNCallArgsPos() const { return NumDefs + NCallArgsPos; }
 
   /// Get starting index of non call related arguments
   /// (calling convention, statepoint flags, vm state and gc state).
   unsigned getVarIdx() const {
-    return MI->getOperand(NCallArgsPos).getImm() + MetaEnd;
+    return MI->getOperand(NumDefs + NCallArgsPos).getImm() + MetaEnd + NumDefs;
   }
 
   /// Get index of Calling Convention operand.
   unsigned getCCIdx() const { return getVarIdx() + CCOffset; }
 
   /// Get index of Flags operand.
   unsigned getFlagsIdx() const { return getVarIdx() + FlagsOffset; }
 
   /// Get index of Number Deopt Arguments operand.
   unsigned getNumDeoptArgsIdx() const {
     return getVarIdx() + NumDeoptOperandsOffset;
   }
 
   /// Return the ID for the given statepoint.
-  uint64_t getID() const { return MI->getOperand(IDPos).getImm(); }
+  uint64_t getID() const { return MI->getOperand(NumDefs + IDPos).getImm(); }
 
   /// Return the number of patchable bytes the given statepoint should emit.
   uint32_t getNumPatchBytes() const {
-    return MI->getOperand(NBytesPos).getImm();
+    return MI->getOperand(NumDefs + NBytesPos).getImm();
   }
 
   /// Return the target of the underlying call.
   const MachineOperand &getCallTarget() const {
-    return MI->getOperand(CallTargetPos);
+    return MI->getOperand(NumDefs + CallTargetPos);
   }
 
   /// Return the calling convention.
   CallingConv::ID getCallingConv() const {
     return MI->getOperand(getCCIdx()).getImm();
   }
 
   /// Return the statepoint flags.
   uint64_t getFlags() const { return MI->getOperand(getFlagsIdx()).getImm(); }
 
 private:
   const MachineInstr *MI;
+  unsigned NumDefs;
 };
 
 class StackMaps {
 public:
   struct Location {
     enum LocationType {
       Unprocessed,
       Register,

llvm/lib/CodeGen/MachineVerifier.cpp

 void
 MachineVerifier::visitMachineOperand(const MachineOperand *MO, unsigned MONum) {
   const MachineInstr *MI = MO->getParent();
   const MCInstrDesc &MCID = MI->getDesc();
   unsigned NumDefs = MCID.getNumDefs();
   if (MCID.getOpcode() == TargetOpcode::PATCHPOINT)
     NumDefs = (MONum == 0 && MO->isReg()) ? NumDefs : 0;
 
+  if (MCID.getOpcode() == TargetOpcode::STATEPOINT)
+    NumDefs = MI->getNumDefs();
+
   // The first MCID.NumDefs operands must be explicit register defines
   if (MONum < NumDefs) {
     const MCOperandInfo &MCOI = MCID.OpInfo[MONum];
     if (!MO->isReg())
       report("Explicit definition must be a register", MO, MONum);
     else if (!MO->isDef() && !MCOI.isOptionalDef())
       report("Explicit definition marked as use", MO, MONum);
     else if (MO->isImplicit())