On Mon, May 03, 2021 at 10:04:20AM +0200, Eric Botcazou wrote:
> Hi,
>
> when a call to a function is inlined and takes a parameter whose type is not
> gimple_reg, a variable is created in the caller to hold a copy of the argument
> passed in the call with the following comment:
>
> /* We may produce non-gimple trees by adding NOPs or introduce
> invalid sharing when operand is not really constant.
> It is not big deal to prohibit constant propagation here as
> we will constant propagate in DOM1 pass anyway. *
>
> Of course the second sentence of the comment does not apply to non-gimple_reg
> values, unless they get SRAed later, because we do not do constant propagation
> for them. This for example prevents two identical calls to a pure function
> from being merged in the attached Ada testcase.
>
> Therefore the attached patch attempts to reuse a read-only or non-addressable
> local DECL of the caller, the hitch being that expand_call_inline needs to be
> prevented from creating a CLOBBER for the cases where it ends uo being reused.
I'm afraid the inliner would need to prove the to be inlined callee doesn't
modify its own copy of the variable too, because if it modifies it (at least
in C/C++ const can be cast away), then this introduces wrong-code, see
PR100994 for details.
> Tested on x86-64/Linux, OK for the mainline?
>
>
> 2021-05-03 Eric Botcazou <ebotca...@adacore.com>
>
> * tree-inline.c (setup_one_parameter): Do not create a variable if the
> value is either a read-only DECL or a non-addressable local variable.
> Register the variable thus reused instead of creating a new one.
> (expand_call_inline): Do not generate a CLOBBER for these variables.
>
>
> 2021-05-03 Eric Botcazou <ebotca...@adacore.com>
>
> * gnat.dg/opt94.adb: New test.
> * gnat.dg/opt94_pkg.ads, opt94.adb: New helper.
Jakub
