Type-Directed Flow Analysis for Typed Intermediate Languages

Flow analysis is especially valuable for optimizing functional languages because control-ow information is not syntactically apparent in higher-order programs. Flow analyses typically operate on untyped languages. However, recent compilers for typed functional languages such as ML and Haskell use a typed intermediate language to expose data representations for optimization. This paper presents a polyvariant ow analysis framework for the predicative subset of system F , a common basis for typed intermediate languages. Analyses in this framework can take advantage of types to analyze programs more precisely. We study a speciic analysis called SRT that uses types to control polyvariance. We prove that SRT respects types: whenever it assigns abstract value ^ v to a variable and the type system assigns type to the same variable, then ^ v] ] ] ], where ] ] denotes a set of values. SRT does not terminate for some programs. We present several variants of SRT that are better suited to practical use.