Outline pieces of a function into their own functions. This transformation is useful, for example, to break a large, virtualized, function into smaller, less conspicuous, pieces. Four different splitting methods are supported. The order in which they are tried can affect the naturalness of the resulting code.



--Transform Split Outline pieces of a function
--SplitKinds top, block, deep, recursive, level, inside Comma-separated list specifying the order in which different split methods are attempted. Default=top,block,deep,recursive.
  • top = split the top-level list of statements into two functions funcname_split_1 and funcname_split_2.
  • block = split a basic block (list of assignment and call statements) into two functions.
  • deep = split out a nested control structure of at least height>2 into its own function funcname_split_1.
  • recursive = same as block, but calls to split functions are also allowed to be split out.
  • level = split out a statement at a level specified by --SplitLevel.
  • inside = split out a statement at the innermost nesting level.
--SplitCount INTSPEC How many times to attempt the split. Default=1.
--SplitName string If set, the split out functions will be named prefix_name_number, otherwise they will be named prefix_originalName_split_number. Default=top,block,deep,recursive.
--SplitLevel INTSPEC Levels which could be split out when specifying --SplitKinds=level. Default=1.


This command first tries to split function foo at most 100 times, then applies the block split transformation to the resulting outlined function. Note the use of a regular expression to specify the names of the functions that were generated in the first transformation:

tigress  \
   --Transform=split --Seed=0 --SplitKinds=deep,block,top --SplitCount=100 --Functions=foo \
   --Transform=Split --Seed=0 --SplitKinds=block --SplitCount=100 --Functions=/.\*foo_split.\*/ \
   --out=foo prog.c
Split up fib in as many pieces as possible.
tigress --Verbosity=1  \
   --Transform=Split --Seed=0 --SplitKinds=deep,block,top --SplitCount=100 --Functions=fib \
   --Transform=CleanUp --CleanUpKinds=annotations \
   --out=gen/split1.c test1.c 
Split ⇒ Split
Split up fib in as many pieces as possible, and then split up the resulting functions as well.
tigress --Verbosity=1  \
   --Transform=Split --Seed=0 --SplitKinds=block,top,deep --SplitCount=10 --Functions=fib --SplitName=SPLIT \
   --Transform=Split --Seed=0 --SplitKinds=block --SplitCount=10 --Functions=/.\*SPLIT.\*/ \
   --Transform=CleanUp --CleanUpKinds=annotations \
   --out=gen/split2.c test1.c