GCC parameter optimisation help

GCC parameter optimisation help

[vikramsp]

I've observed that --param name=value type of options are
having default, min, max values but not all. eg. max-goto-duplication-insns
has default 8 but max-delay-slot-insn-search has none. My problem is:

1. Do all parameter have limits and defaults?
2. If yes why they are not documented?
3. If no how to find the best values?

Regard,
vikram

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Re: GCC parameter optimisation help

[Ian Lance Taylor]

vikramsp <vikram2rhyme@gmail.com> writes:

> I've observed that --param name=value type of options are
> having default, min, max values but not all. eg. max-goto-duplication-insns
> has default 8 but max-delay-slot-insn-search has none. My problem is:
>
> 1. Do all parameter have limits and defaults?

They all have defaults, of course.  They do not all have limits.

> 2. If yes why they are not documented?

Either because the of a documentation bug or because the default is
obvious.  I agree that the default for max-delay-slot-insn-search should
be documented.  It is 100.

> 3. If no how to find the best values?

Start by looking at gcc/params.def.

The --param options are generally intended for expert use by people
familiar with how the compiler works.  The -f options intended for use
by people not deeply familiar with the compiler.  This is not an excuse
for poor documentations, but some of the --param options are quite
difficult to document precisely.

Ian