This open-label, multicenter, Phase I, dose-escalation study will evaluate the safety, tolerability, and pharmacokinetics (PK) of GDC-0575 administered alone or in combination with gemcitabine in participants with refractory solid tumors or lymphoma. In Stage 1, cohorts of participants will receive multiple ascending oral doses of GDC-0575 alone or in combination with intravenous gemcitabine. In Stage 2, participants will receive GDC-0575 orally in combination with intravenous gemcitabine at or below the maximum tolerated dose determined in Stage 1. Anticipated time on study treatment is until disease progression or unacceptable toxicity occurs, up to approximately 5 years.