[GISel]: Fix one more CSE Non determinism

[aditya_nandakumar]

Summary

Sometimes we can have the following code

x:gpr(s32) = G_OP

Say we build G_OP2 to the same x and then delete the previous instruction. Using something like

Register X = ...;
auto NewMIB = CSEBuilder.buildOp2(X, ... args);

Currently there's a mismatch in how NewMIB is profiled and inserted into the CSEMap (ie it doesn't consider register bank/register class along with type).Unify the profiling by refactoring and calling the common method.

This was found by turning on the CSEInfo::verify in at the end of each of our GISel passes which turns inconsistent state/non determinism in CSEing into crashes which likely usually indicates missing calls to Observer on mutations (the most common case). Here non determinism usually means not cseing sometimes, but almost never about producing incorrect code.
Also this patch adds this verification at the end of the combiners as well.

[aditya_nandakumar]

rG5c2db1655

llvm/include/llvm/CodeGen/GlobalISel/CSEInfo.h

public:
   const GISelInstProfileBuilder &addNodeIDRegType(const Register) const;
 
   const GISelInstProfileBuilder &
   addNodeIDRegType(const TargetRegisterClass *RC) const;
   const GISelInstProfileBuilder &addNodeIDRegType(const RegisterBank *RB) const;
 
   const GISelInstProfileBuilder &addNodeIDRegNum(Register Reg) const;
 
+  const GISelInstProfileBuilder &addNodeIDReg(Register Reg) const;
+
   const GISelInstProfileBuilder &addNodeIDImmediate(int64_t Imm) const;
   const GISelInstProfileBuilder &
   addNodeIDMBB(const MachineBasicBlock *MBB) const;
 
   const GISelInstProfileBuilder &
   addNodeIDMachineOperand(const MachineOperand &MO) const;
 
   const GISelInstProfileBuilder &addNodeIDFlag(unsigned Flag) const;

llvm/lib/CodeGen/GlobalISel/CSEInfo.cpp

 
 const GISelInstProfileBuilder &
 GISelInstProfileBuilder::addNodeIDFlag(unsigned Flag) const {
   if (Flag)
     ID.AddInteger(Flag);
   return *this;
 }
 
-const GISelInstProfileBuilder &GISelInstProfileBuilder::addNodeIDMachineOperand(
-    const MachineOperand &MO) const {
-  if (MO.isReg()) {
-    Register Reg = MO.getReg();
-    if (!MO.isDef())
-      addNodeIDRegNum(Reg);
-    LLT Ty = MRI.getType(Reg);
-    if (Ty.isValid())
-      addNodeIDRegType(Ty);
+const GISelInstProfileBuilder &
+GISelInstProfileBuilder::addNodeIDReg(Register Reg) const {
 
-    if (const RegClassOrRegBank &RCOrRB = MRI.getRegClassOrRegBank(Reg)) {
-      if (const auto *RB = RCOrRB.dyn_cast<const RegisterBank *>())
-        addNodeIDRegType(RB);
-      else if (const auto *RC = RCOrRB.dyn_cast<const TargetRegisterClass *>())
-        addNodeIDRegType(RC);
-    }
+  return *this;
+}
+
+const GISelInstProfileBuilder &GISelInstProfileBuilder::addNodeIDMachineOperand(
+    const MachineOperand &MO) const {
+  if (MO.isReg()) {
+    Register Reg = MO.getReg();
+    if (!MO.isDef())
+      addNodeIDRegNum(Reg);
 
+    // Profile the register properties.
+    addNodeIDReg(Reg);
     assert(!MO.isImplicit() && "Unhandled case");
   } else if (MO.isImm())
     ID.AddInteger(MO.getImm());
   else if (MO.isCImm())
     ID.AddPointer(MO.getCImm());
   else if (MO.isFPImm())
     ID.AddPointer(MO.getFPImm());
   else if (MO.isPredicate())

llvm/lib/CodeGen/GlobalISel/CSEMIRBuilder.cpp

 }
 
 void CSEMIRBuilder::profileDstOp(const DstOp &Op,
                                  GISelInstProfileBuilder &B) const {
   switch (Op.getDstOpKind()) {
   case DstOp::DstType::Ty_RC:
     B.addNodeIDRegType(Op.getRegClass());
     break;
+  case DstOp::DstType::Ty_Reg: {
+    // Regs can have LLT&(RB|RC). If those exist, profile them as well.
+    B.addNodeIDReg(Op.getReg());
+    break;
+  }
   default:
     B.addNodeIDRegType(Op.getLLTTy(*getMRI()));
     break;
   }
 }
 
 void CSEMIRBuilder::profileSrcOp(const SrcOp &Op,
                                  GISelInstProfileBuilder &B) const {

llvm/lib/CodeGen/GlobalISel/Combiner.cpp

while (!WorkList.empty()) {
       MachineInstr *CurrInst = WorkList.pop_back_val();
       LLVM_DEBUG(dbgs() << "\nTry combining " << *CurrInst;);
       Changed |= CInfo.combine(WrapperObserver, *CurrInst, B);
       Observer.reportFullyCreatedInstrs();
     }
     MFChanged |= Changed;
   } while (Changed);
 
+  assert(!CSEInfo || !errorToBool(CSEInfo->verify()) &&
+                         "CSEInfo is not consistent. Likely missing calls to "
+                         "observer on mutations");
   return MFChanged;
 }