[mlir] Allow fallback from file line col range to loc (llvm#124321)

This was discussed during the original review but I made it stricter
than discussed. Making it a pure view but adding a helper for bytecode
serialization (I could avoid the helper, but it ends up with more logic
and stronger coupling).

Author: jpienaar

mlir/include/mlir/IR/BuiltinDialectBytecode.td

@@ -104,15 +104,15 @@ def FileLineColRange : DialectAttribute<(attr
     WithPrinter<"writeFileLineColRangeLocs($_writer, $_name)">>>>:$rawLocData
 )> {
   let cBuilder = "getFileLineColRange(context, filename, rawLocData)";
-  let printerPredicate = "!::llvm::isa<FileLineColLoc>($_val)";
+  let printerPredicate = "!isStrictFileLineColLoc($_val)";
 }
 
 def FileLineColLoc : DialectAttribute<(attr
   StringAttr:$filename,
   VarInt:$start_line,
   VarInt:$start_column
 )> {
-  let printerPredicate = "::llvm::isa<FileLineColLoc>($_val)";
+  let printerPredicate = "isStrictFileLineColLoc($_val)";
 }
 }
 

mlir/include/mlir/IR/Location.h

@@ -177,7 +177,7 @@ class FusedLocWith : public FusedLoc {
 /// column number. This is similar to the type of location that you get from
 /// most source languages.
 ///
-/// FileLineColLoc is a FileLineColRange with exactly one line and column.
+/// FileLineColLoc is a view to FileLineColRange with one line and column.
 class FileLineColLoc : public FileLineColRange {
 public:
   using FileLineColRange::FileLineColRange;
@@ -190,11 +190,12 @@ class FileLineColLoc : public FileLineColRange {
   StringAttr getFilename() const;
   unsigned getLine() const;
   unsigned getColumn() const;
-
-  /// Methods for support type inquiry through isa, cast, and dyn_cast.
-  static bool classof(Attribute attr);
 };
 
+/// Returns true iff the given location is a FileLineColRange with exactly one
+/// line and column.
+bool isStrictFileLineColLoc(Location loc);
+
 //===----------------------------------------------------------------------===//
 // OpaqueLoc
 //===----------------------------------------------------------------------===//

mlir/lib/IR/Location.cpp

@@ -177,10 +177,8 @@ unsigned FileLineColLoc::getLine() const { return getStartLine(); }
 
 unsigned FileLineColLoc::getColumn() const { return getStartColumn(); }
 
-bool FileLineColLoc::classof(Attribute attr) {
-  // This could also have been for <= 2. But given this is matching previous
-  // behavior, it is left as is.
-  if (auto range = mlir::dyn_cast<FileLineColRange>(attr))
+bool mlir::isStrictFileLineColLoc(Location loc) {
+  if (auto range = mlir::dyn_cast<FileLineColRange>(loc))
     return range.getImpl()->size() == 2;
   return false;
 }

mlir/test/Target/LLVMIR/llvmir-debug.mlir

@@ -115,6 +115,9 @@ llvm.func @func_with_debug(%arg: i64) {
   // CHECK: call void @func_no_debug(), !dbg ![[FILE_LOC:[0-9]+]]
   llvm.call @func_no_debug() : () -> () loc("foo.mlir":1:2)
 
+  // CHECK: call void @func_no_debug(), !dbg ![[FILE_LOC:[0-9]+]]
+  llvm.call @func_no_debug() : () -> () loc("foo.mlir":1:2 to 5:6)
+
   // CHECK: call void @func_no_debug(), !dbg ![[NAMED_LOC:[0-9]+]]
   llvm.call @func_no_debug() : () -> () loc("named"("foo.mlir":10:10))