Add custom type for PseudoSourceValue

[kariddi]

Summary

PseudoSourceValue can be used to attach a target specific value for "well behaved" side-effects lowered from target specific intrinsics.
This is useful whenever there is not an LLVM IR Value around when representing such "well behaved" side-effected operations in backends by attaching a MachineMemOperand with a custom PseudoSourceValue as this makes the scheduler not treating them as "GlobalMemoryObjects" which triggers a logic that makes the operation act like a barrier in the Schedule DAG.

This patch adds another Kind to the PseudoSourceValue object which is "TargetCustom". It indicates a type of PseudoSourceValue that has a target specific meaning (aka. LLVM shouldn't assume any specific usage for such a PSV).

It supports the possibility of having many different kinds of "TargetCustom" PseudoSourceValues.

We had a discussion about if this was valuable or not (in particular because there was a believe that PSV were going away sooner or later) but seems like they are not going anywhere and I think they are useful backend side.

It is not clear the interaction of this with MIRParser (do we need a target hook to parse these?) and I would like a comment from Alex about that :)

[arsenm]

LGTM

[arsenm]

ping

[arsenm]

ping

[Eugene.Zelenko]

Looks like patch was not committed.

llvm/trunk/include/llvm/CodeGen/PseudoSourceValue.h

 public:
   enum PSVKind {
     Stack,
     GOT,
     JumpTable,
     ConstantPool,
     FixedStack,
     GlobalValueCallEntry,
-    ExternalSymbolCallEntry
+    ExternalSymbolCallEntry,
+    TargetCustom
   };
 
 private:
   PSVKind Kind;
   friend raw_ostream &llvm::operator<<(raw_ostream &OS,
                                        const PseudoSourceValue* PSV);
 
   friend class MachineMemOperand; // For printCustom().
 
   /// Implement printing for PseudoSourceValue. This is called from
   /// Value::print or Value's operator<<.
   virtual void printCustom(raw_ostream &O) const;
 
 public:
   explicit PseudoSourceValue(PSVKind Kind);
 
   virtual ~PseudoSourceValue();
 
   PSVKind kind() const { return Kind; }
 
   bool isStack() const { return Kind == Stack; }
   bool isGOT() const { return Kind == GOT; }
   bool isConstantPool() const { return Kind == ConstantPool; }
   bool isJumpTable() const { return Kind == JumpTable; }
+  unsigned getTargetCustom() const {
+    return (Kind >= TargetCustom) ? ((Kind+1) - TargetCustom) : 0;
+  }
 
   /// Test whether the memory pointed to by this PseudoSourceValue has a
   /// constant value.
   virtual bool isConstant(const MachineFrameInfo *) const;
 
   /// Test whether the memory pointed to by this PseudoSourceValue may also be
   /// pointed to by an LLVM IR Value.
   virtual bool isAliased(const MachineFrameInfo *) const;

llvm/trunk/lib/CodeGen/MIRPrinter.cpp

case PseudoSourceValue::GlobalValueCallEntry:
       cast<GlobalValuePseudoSourceValue>(PVal)->getValue()->printAsOperand(
           OS, /*PrintType=*/false, MST);
       break;
     case PseudoSourceValue::ExternalSymbolCallEntry:
       OS << "call-entry $";
       printLLVMNameWithoutPrefix(
           OS, cast<ExternalSymbolPseudoSourceValue>(PVal)->getSymbol());
       break;
+    case PseudoSourceValue::TargetCustom:
+      llvm_unreachable("TargetCustom pseudo source values are not supported");
+      break;
     }
   }
   printOffset(Op.getOffset());
   if (Op.getBaseAlignment() != Op.getSize())
     OS << ", align " << Op.getBaseAlignment();
   auto AAInfo = Op.getAAInfo();
   if (AAInfo.TBAA) {
     OS << ", !tbaa ";