[NFC][IntrRefLDV] Improve the Value printing

[djtodoro]

Summary

Basically, this just improves the dump of the Value stored within a location.

If the defining instruction number is zero, it means it is "live-in".

Before the patch:

ESI --> bb 0 inst 0 loc ESI

After:

ESI --> Value{bb: 0, inst: live-in, loc: ESI}

This is an NFC.

[jmorse]

LGTM, anything and everything in this vein much appreciated.

[djtodoro]

@jmorse Thanks. :)

llvm/lib/CodeGen/LiveDebugValues/InstrRefBasedImpl.cpp

public:
   bool operator==(const ValueIDNum &Other) const {
     return std::tie(BlockNo, InstNo, LocNo) ==
            std::tie(Other.BlockNo, Other.InstNo, Other.LocNo);
   }
 
   bool operator!=(const ValueIDNum &Other) const { return !(*this == Other); }
 
   std::string asString(const std::string &mlocname) const {
-    return Twine("bb ")
-        .concat(Twine(BlockNo).concat(Twine(" inst ").concat(
-            Twine(InstNo).concat(Twine(" loc ").concat(Twine(mlocname))))))
+    return Twine("Value{bb: ")
+        .concat(Twine(BlockNo).concat(
+            Twine(", inst: ")
+                .concat((InstNo ? Twine(InstNo) : Twine("live-in"))
+                            .concat(Twine(", loc: ").concat(Twine(mlocname)))
+                            .concat(Twine("}")))))
         .str();
   }
 
   static ValueIDNum EmptyValue;
 };
 
 } // end anonymous namespace