[flang] [llvm] [flang] Implement FSEEK and FTELL (PR #133003)

[Eugene Epshteyn via llvm-commits]

================
@@ -4117,6 +4128,69 @@ void IntrinsicLibrary::genFree(llvm::ArrayRef<fir::ExtendedValue> args) {
   fir::runtime::genFree(builder, loc, fir::getBase(args[0]));
 }
 
+// FSEEK
+fir::ExtendedValue
+IntrinsicLibrary::genFseek(std::optional<mlir::Type> resultType,
+                           llvm::ArrayRef<fir::ExtendedValue> args) {
+  assert((args.size() == 4 && !resultType.has_value()) ||
+         (args.size() == 3 && resultType.has_value()));
+  mlir::Value unit = fir::getBase(args[0]);
+  mlir::Value offset = fir::getBase(args[1]);
+  mlir::Value whence = fir::getBase(args[2]);
+  if (!unit)
+    fir::emitFatalError(loc, "expected UNIT argument");
+  if (!offset)
+    fir::emitFatalError(loc, "expected OFFSET argument");
+  if (!whence)
+    fir::emitFatalError(loc, "expected WHENCE argument");
+  mlir::Value statusValue =
+      fir::runtime::genFseek(builder, loc, unit, offset, whence);
+  if (resultType.has_value()) { // function
+    return statusValue;
----------------
eugeneepshteyn wrote:

FWIW, Jean had me change similar return to `return builder.createConvert(loc, *resultType, statusValue);`

https://github.com/llvm/llvm-project/pull/133003