Not
exactly. But this also depends on the specific kind of liberalism you are speaking of.
From the Catholic Encyclopedia, which gives a good overview on the subject of Liberalism:
The most fundamental principle asserts an absolute and unrestrained freedom of thought, religion, conscience, creed, speech, press, and politics. The necessary consequences of this are, on the one hand, the abolition of the Divine right and of every kind of authority derived from God; the relegation of religion from the public life into the private domain of one's individual conscience; the absolute ignoring of Christianity and the Church as public, legal, and social institutions; on the other hand, the putting into practice of the absolute autonomy of every man and citizen, along all lines of human activity, and the concentration of all public authority in one "sovereignty of the people". This sovereignty of the people in all branches of public life as legislation, administration, and jurisdiction, is to be exercised in the name and by order of all the citizens, in such a way, that all should have share in and a control over it.
Early Catholic liberals, most prominently Lamennais, did not directly share the same theological and philosophical opinions as those of the modernists. Modernism as such is also much harder to define, since it embraces a wide field of modern errors in many different forms, the most noticeable could be the denial of dogma. A liberalist would not necessarily deny the existence of dogma or ecclesiastical authority, even though their system of thought would logically lead to this conclusion, as seen above.
Still, in the very beginnings of Liberalism connections with Jansenism can be found. And the synthesis of Jansenism and Liberalism could already be called the prototype of modernism.
Pius X. also condemned some liberalist proposition as modernist errors. As you can see, every modernist is a liberal, but not every liberal a modernist - but I think there is hardly a non-modernist liberal in these days, as this position would at some point be self-contradictory.