introduce -fcallgraph-info option

[Richard Biener]

On Sun, 27 Oct 2019, Alexandre Oliva wrote:

> On Oct 26, 2019, Alexandre Oliva <oliva@adacore.com> wrote:
> 
> > E.g., the reason we gather expanded calls rather than just use
> > cgraph_edges is that the latter would dump several "calls" that are
> > builtins expanded internally by the compiler, and would NOT dump other
> > ops that are expanded as (lib)calls.
> 
> It occurred to me that we could reuse most cgraph edges and avoid
> duplicating them in the callees vec, namely those that aren't builtins
> or libcalls.  Those that are builtins might or might not become actual
> calls, so we disregard the cgraph_edges and record them in the vec
> instead.  Those that are libcalls (builtins in a different sense)
> introduced during expand are not even present in the cgraph edges, so we
> record them in the vec as well.  Here's the patch that implements this.
> 
> Regstrapped on x86_64-linux-gnu.  Ok to install?

<...>

> --- a/gcc/common.opt
> +++ b/gcc/common.opt
> @@ -1091,6 +1091,14 @@ fbtr-bb-exclusive
>  Common Ignore
>  Does nothing.  Preserved for backward compatibility.
>  
> +fcallgraph-info
> +Common Report RejectNegative Var(flag_callgraph_info) Init(NO_CALLGRAPH_INFO);
> +Output callgraph information on a per-file basis
> +
> +fcallgraph-info=
> +Common Report RejectNegative Joined
> +Output callgraph information on a per-file basis with decorations
> +
>  fcall-saved-
>  Common Joined RejectNegative Var(common_deferred_options) Defer
>  -fcall-saved-<register>	Mark <register> as being preserved across functions.
> diff --git a/gcc/doc/invoke.texi b/gcc/doc/invoke.texi
> index 1407d019d1404..545b842eade71 100644
> --- a/gcc/doc/invoke.texi
> +++ b/gcc/doc/invoke.texi
> @@ -583,8 +583,9 @@ Objective-C and Objective-C++ Dialects}.
>  @item Developer Options
>  @xref{Developer Options,,GCC Developer Options}.
>  @gccoptlist{-d@var{letters}  -dumpspecs  -dumpmachine  -dumpversion @gol
> --dumpfullversion  -fchecking  -fchecking=@var{n}  -fdbg-cnt-list @gol
> --fdbg-cnt=@var{counter-value-list} @gol
> +-dumpfullversion  -fcallgraph-info@r{[}=su,da@r{]}
> +-fchecking  -fchecking=@var{n}
> +-fdbg-cnt-list @gol  -fdbg-cnt=@var{counter-value-list} @gol
>  -fdisable-ipa-@var{pass_name} @gol
>  -fdisable-rtl-@var{pass_name} @gol
>  -fdisable-rtl-@var{pass-name}=@var{range-list} @gol
> @@ -14533,6 +14534,18 @@ The files are created in the directory of the output file.
>  
>  @table @gcctabopt
>  
> +@item -fcallgraph-info
> +@itemx -fcallgraph-info=@var{MARKERS}
> +@opindex fcallgraph-info
> +Makes the compiler output callgraph information for the program, on a
> +per-file basis.  The information is generated in the common VCG format.

I guess you need to elaborate on 'per-file'.  With LTO as far as I
understand you'll get the graph per LTRANS unit (did you check
where the output is generated?).

Is this mainly a debugging tool or does it serve a different purpose?

Otherwise OK.

Thanks,
Richard.

> +It can be decorated with additional, per-node and/or per-edge information,
> +if a list of comma-separated markers is additionally specified.  When the
> +@code{su} marker is specified, the callgraph is decorated with stack usage
> +information; it is equivalent to @option{-fstack-usage}.  When the @code{da}
> +marker is specified, the callgraph is decorated with information about
> +dynamically allocated objects.