Plugins

Semantic constant folding

Overview

The Semantic constant folding plug-in produces an output program where C expressions which are established as constant by the Value analysis plug-in are replaced by their value. Because it relies on EVA, it is able to do more of these simplifications than a syntactic analysis would. The output program is guaranteed to be compilable C code, and to have the same semantics as the original program.

The plug-in performs propagation of constant integers and addresses, but at this time, it does not handle floating-point values.

Usage

The command-line options related to constant folding are:

  • -semantic-const-folding
    activate semantic constant folding and pretty print the new source code.
  • -semantic-const-fold f1,...,fn
    replace constant expressions in functions f1,...,fn.
  • -cast-from-constant
    allow introduction of new casts from a folded constant.
Example

Consider the code fragment:

	  p = &x;
	  x = 3;
	  send(*p+4);
	

The Semantic constant folding plug-in produces:

	  p = &x;
	  x = 3;
	  send(7);
	

If you need to remove the (now useless) first two statements, you may make use of the Spare Code analysis plug-in.