An problematic interaction between a call created by gimple_build_call and inlining

[Gary Oblock]

Thank you Richard.

I feel a bit dumb because I'm well aware of the GCC philosophy to have
any new code produced update the state.  Of course I didn't know the
commands to do this for the call graph (which I really appreciate you giving.)

However, the real reason I'm sending a reply is this. Are there any surprising
cases in IPA where GCC violates its philosophy and actually regenerates the
information?

Thanks again,

Gary

________________________________
From: Richard Biener <richard.guenther@gmail.com>
Sent: Wednesday, July 1, 2020 12:27 AM
To: Gary Oblock <gary@amperecomputing.com>
Cc: gcc@gcc.gnu.org <gcc@gcc.gnu.org>
Subject: Re: An problematic interaction between a call created by gimple_build_call and inlining

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On Wed, Jul 1, 2020 at 7:49 AM Gary Oblock via Gcc <gcc@gcc.gnu.org> wrote:
>
> I'm trying to generate calls to "free" on the fly at ipa time.
>
> I've tried several things (given below) but they both fail
> in expand_call_inline in tree-inline.c on this gcc_checking_assert:
>
>   cg_edge = id->dst_node->get_edge (stmt);
>   gcc_checking_assert (cg_edge);

It simply means you are operating at a point where we expect
callgraph edges to be present but you fail to update the callgraph
for your added function call.  it might be as easy as calling

cgraph_node::get (cfun->decl)->create_edge (cgraph_node::get_create
(fndecl_free), free_call, gimple_bb (free_call)->count);

> Now, I've tried using the built in free via:
>
>   tree fndecl_free = builtin_decl_explicit( BUILT_IN_FREE);
>   // Note to_free is set between here and the call by an assign
>   tree to_free =
>     make_temp_ssa_name( reorg_pointer_type, NULL, "malloc_to_free");
>   .
>   .
>   gcall *free_call = gimple_build_call( fndecl_free, 1, to_free);
>
> or building the fndecl from scrath:
>
>   tree fntype = build_function_type ( free_return_type, param_type_list);
>   tree fnname = get_identifier ( "free");
>   tree fndecl_free =
>     build_decl ( input_location, FUNCTION_DECL, fnname, fntype);
>   gcall *free_call = gimple_build_call( fndecl_free, 1, to_free);
>
> Note, I was able to get something similar to work for "malloc" by
> using the fndecl I extracted from an existing malloc call.
>
> Your advice on how to build a fndecl that doesn't have this
> problem is appreciated.
>
> Thanks,
>
> Gary Oblock
>
>
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