[MLIR] Enable conversion from llvm::SMLoc to mlir::Location with OpAsmParser.

[ulysseB]

Summary

DialectAsmParser already allows converting an llvm::SMLoc location to a
mlir::Location location. This commit adds the same functionality to OpAsmParser.
Implementation is copied from DialectAsmParser.

mlir/include/mlir/IR/OpImplementation.h

public:
 
   /// Return the number of declared SSA results.  This returns 4 for the foo.op
   /// example in the comment for `getResultName`.
   virtual size_t getNumResults() const = 0;
 
   /// Return the location of the original name token.
   virtual llvm::SMLoc getNameLoc() const = 0;
 
+  /// Re-encode the given source location as an MLIR location and return it.
+  /// Note: This method should only be used when a `Location` is necessary, as
+  /// the encoding process is not efficient.
+  virtual Location getEncodedSourceLoc(llvm::SMLoc loc) = 0;
+
   // These methods emit an error and return failure or success. This allows
   // these to be chained together into a linear sequence of || expressions in
   // many cases.
 
   /// Parse an operation in its generic form.
   /// The parsed operation is parsed in the current context and inserted in the
   /// provided block and insertion point. The results produced by this operation
   /// aren't mapped to any named value in the parser. Returns nullptr on

mlir/lib/Parser/Parser.cpp

size_t getNumResults() const override {
     size_t count = 0;
     for (auto &entry : resultIDs)
       count += std::get<1>(entry);
     return count;
   }
 
   llvm::SMLoc getNameLoc() const override { return nameLoc; }
 
+  /// Re-encode the given source location as an MLIR location and return it.
+  Location getEncodedSourceLoc(llvm::SMLoc loc) override {
+    return parser.getEncodedSourceLocation(loc);
+  }
+
   //===--------------------------------------------------------------------===//
   // Token Parsing
   //===--------------------------------------------------------------------===//
 
   /// Parse a `->` token.
   ParseResult parseArrow() override {
     return parser.parseToken(Token::arrow, "expected '->'");
   }