Catalysis of the reaction: 1-phosphatidyl-1D-myo-inositol = D-myo-inositol 1,2-cyclic phosphate + diacylglycerol.
1-phosphatidyl-1D-myo-inositol diacyl-sn-glycerol-lyase (1D-myo-inositol-1,2-cyclic-phosphate-forming)