Denotational semantics for program analysis

4 1.INTRODUCTIO NThe denotational semantics approach to formal specification of programming languages contain s detailed information for the implementation of that language, unlike the axiomatic semantics approach .This feature makes the denotational semantics approach more flexible than the operational approach in it s not having any specific abstract machine .A compiler can be systematically constructed from the formal denotational semantics specification by applying the function of the specification to the source program .This is called a compile-evaluate approach for denotational semantics or compiler generation .Compile r generation addresses the issue of proving compiler correctness .This paper describes how to apply denotational semantics to program analysis, specifically cod e optimization, and to the parallel implementation of sequential imperative languages .In considering cod e optimization, the object code derived from the denotational semantics specification is a set of denotations which we claim can be further optimized by partial evaluation .Partial evaluation [5] of a subject progra m evaluates that program with respect to only a portion of its input parameters, resulting in a residua l program .By definition, running the residual program on any remaining input yields the same result a s running the original subject program on all of its input .>From this point of view then, partial evaluatio n is nothing but a special case of program transformation for the purpose of optimization .Partial evaluatio n performs those simplification steps which are not dependent on execution-time values .To determine whic h simplifications to perform, we make an expression unfrozen if it can be simplified before execution-time .A frozen expression may not be simplified .Declarations, environments, and store algebras are all mad e unfrozen resulting in more efficient code .Code optimization on declarations, type checking, constant folding , and inline function expansion will be carried out .