gccint: Dump setup

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1 9.6.1 Dump setup
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1 A dump_manager class is defined in 'dumpfile.h'.  Various passes
1 register dumping pass-specific information via 'dump_register' in
1 'passes.c'.  During the registration, an optimization pass can select
1 its optimization group (⇒Optimization groups).  After that
1 optimization information corresponding to the entire group (presumably
1 from multiple passes) can be output via command-line switches.  Note
1 that if a pass does not fit into any of the pre-defined groups, it can
1 select 'OPTGROUP_NONE'.
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1  Note that in general, a pass need not know its dump output file name,
1 whether certain flags are enabled, etc.  However, for legacy reasons,
1 passes could also call 'dump_begin' which returns a stream in case the
1 particular pass has optimization dumps enabled.  A pass could call
1 'dump_end' when the dump has ended.  These methods should go away once
1 all the passes are converted to use the new dump infrastructure.
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1  The recommended way to setup the dump output is via 'dump_start' and
1 'dump_end'.
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