[PATCH] pass filtering for -fopt-info

[Sharad Singhai <singhai at google dot com>]

As per discussion in http://gcc.gnu.org/ml/gcc/2012-10/msg00225.html,
I have added the -fopt-info pass filtering in the attached patch.

The basic idea is that there are optimization pass groups and a user
can selectively enable dumps for these group(s) via command-line
syntax. Currently, I define the following optimization groups: 'loop',
'lto', 'inline', 'vec', and 'omp'. A pass can be in multiple groups.

If a pass doesn't explicitly specify an optimization group, (denoted
by OPTGROUP_NONE) then a group is assigned based on the pass type.
These three are the obvious implicit groups: 'tree', 'ipa', and 'rtl'.

Also there is a catch-all group, called 'optall'.

The options for -fopt-info dumps verbosity remain 'optimized',
'missed', 'note', and 'all'. Since these two types of options,
verbosity and optimization groups are non-overlapping, I have decided
to freely mix them. Something like this works as expected, i.e., dump
missed vectorizer info into vec.missed.

gcc ... -fopt-info-vec-missed=vec.missed

which is equivalent to

gcc ... -fopt-info-missed-vec=vec.missed

However, the order still matters, and it can be somewhat confusing. For example,

gcc -fopt-info-vec-missed=vec.miss -fopt-info-vec-optimized=vec.opt

will dump missed and optimized vectorizer info into vec.opt, while no
vec.miss is produced. This is due to the fact that the latter group
specifier, 'vec' overrides the first one. However, the 'missed' and
'optimized' are both honored as there is no conflict there. This is
somewhat confusing. Hopefully, this type of usage would not be common.

I have updated the documentation to include -fopt-info examples, and
added some details about -fopt-info command line conflicts.

Thanks,
Sharad

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