Named phi

[cdonovick]

Adds utility function gen_free_name

changes ssa:

• ssa now takes an optional argument phi which can be either a function or a string
  • default value "phi"
  • if phi is a string then ssa will assume that such a name exists in the environment of the decorated function
  • if phi is a function then ssa will generate a new name and associate phi with the name in the generated code
• moves the stripping of decorators from convert_tree_to_ssa to ssa

[coveralls]

Pull Request Test Coverage Report for Build 1895

• 39 of 47 (82.98%) changed or added relevant lines in 2 files are covered.
• No unchanged relevant lines lost coverage.
• Overall coverage increased (+0.03%) to 74.227%

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Changes Missing Coverage	Covered Lines	Changed/Added Lines	%
magma/ast_utils.py	22	30	73.33%

Totals
Change from base Build 1892:	0.03%
Covered Lines:	4271
Relevant Lines:	5754

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💛 - Coveralls

[leonardt]

Should we add a timeout (e.g. if c >= 1000: raise Exception). Unlikely to come up and would incur a performance cost, but you never know?

[cdonovick]

As python ints don't overflow don't see the need to give up.

[leonardt]

I just realized we can assume that the space of names is finite, so we will eventually find a name.

[leonardt]

(because the length of the program must be finite)

[leonardt]

LGTM