On Fri, 8 Nov 2024, Richard Sandiford wrote:
> For the aarch64 simd clones patches, it would be useful to be able to
> push a function declaration onto the cfun stack, even though it has no
> function body associated with it. That is, we want cfun to be null,
> current_function_decl to be the decl itself, and the target and
> optimisation flags to reflect the declaration.
>
> This patch adds a push/pop_function_decl pair to do that.
>
> I think the more direct way of doing what I want to do under the
> existing interface would have been:
>
> push_cfun (nullptr);
> invoke_set_current_function_hook (fndecl);
> pop_cfun ();
>
> where invoke_set_current_function_hook would need to become public.
> But it seemed safer to use the higher-level routines, since it makes
> sure that the target/optimisation changes are synchronised with the
> function changes. In particular, if cfun was null before the
> sequence above, the pop_cfun would leave the flags unchanged,
> rather than restore them to the state before the push_cfun.
>
> I realise this might seem a bit clunky though, so please let me know
> if you think there's a cleaner way. I did briefly consider trying
> to clean up all the cfun/current_function_decl stuff, but I don't think
> I'll have time for that before stage 1.
>
> Bootstrapped & regression-tested on aarch64-linux-gnu. OK for trunk?
I think this is reasonable, thus OK unless you hear otherwise over
the weekend.
Richard.
> Thanks,
> Richard
>
>
> gcc/
> * function.h (push_function_decl, pop_function_decl): Declare.
> * function.cc (set_function_decl): New function, extracted from...
> (set_cfun): ...here.
> (push_function_decl): New function, extracted from...
> (push_cfun): ...here.
> (pop_cfun_1): New function, extracted from...
> (pop_cfun): ...here.
> (pop_function_decl): New function.
> ---
> gcc/function.cc | 80 +++++++++++++++++++++++++++++++++++++++++--------
> gcc/function.h | 2 ++
> 2 files changed, 69 insertions(+), 13 deletions(-)
>
> diff --git a/gcc/function.cc b/gcc/function.cc
> index 73490f0da10..bf74e1ea208 100644
> --- a/gcc/function.cc
> +++ b/gcc/function.cc
> @@ -4707,40 +4707,74 @@ invoke_set_current_function_hook (tree fndecl)
> }
> }
>
> -/* cfun should never be set directly; use this function. */
> +/* Set cfun to NEW_CFUN and switch to the optimization and target options
> + associated with NEW_FNDECL.
>
> -void
> -set_cfun (struct function *new_cfun, bool force)
> + FORCE says whether we should do the switch even if NEW_CFUN is the current
> + function, e.g. because there has been a change in optimization or target
> + options. */
> +
> +static void
> +set_function_decl (function *new_cfun, tree new_fndecl, bool force)
> {
> if (cfun != new_cfun || force)
> {
> cfun = new_cfun;
> - invoke_set_current_function_hook (new_cfun ? new_cfun->decl :
> NULL_TREE);
> + invoke_set_current_function_hook (new_fndecl);
> redirect_edge_var_map_empty ();
> }
> }
>
> +/* cfun should never be set directly; use this function. */
> +
> +void
> +set_cfun (struct function *new_cfun, bool force)
> +{
> + set_function_decl (new_cfun, new_cfun ? new_cfun->decl : NULL_TREE, force);
> +}
> +
> /* Initialized with NOGC, making this poisonous to the garbage collector. */
>
> static vec<function *> cfun_stack;
>
> -/* Push the current cfun onto the stack, and set cfun to new_cfun. Also set
> - current_function_decl accordingly. */
> +/* Push the current cfun onto the stack, then switch to function NEW_CFUN
> + and FUNCTION_DECL NEW_FNDECL. FORCE is as for set_function_decl. */
>
> -void
> -push_cfun (struct function *new_cfun)
> +static void
> +push_function_decl (function *new_cfun, tree new_fndecl, bool force)
> {
> gcc_assert ((!cfun && !current_function_decl)
> || (cfun && current_function_decl == cfun->decl));
> cfun_stack.safe_push (cfun);
> - current_function_decl = new_cfun ? new_cfun->decl : NULL_TREE;
> - set_cfun (new_cfun);
> + current_function_decl = new_fndecl;
> + set_function_decl (new_cfun, new_fndecl, force);
> }
>
> -/* Pop cfun from the stack. Also set current_function_decl accordingly. */
> +/* Push the current cfun onto the stack and switch to function declaration
> + NEW_FNDECL, which might or might not have a function body. FORCE is as
> for
> + set_function_decl. */
>
> void
> -pop_cfun (void)
> +push_function_decl (tree new_fndecl, bool force)
> +{
> + force |= current_function_decl != new_fndecl;
> + push_function_decl (DECL_STRUCT_FUNCTION (new_fndecl), new_fndecl, force);
> +}
> +
> +/* Push the current cfun onto the stack, and set cfun to new_cfun. Also set
> + current_function_decl accordingly. */
> +
> +void
> +push_cfun (struct function *new_cfun)
> +{
> + push_function_decl (new_cfun, new_cfun ? new_cfun->decl : NULL_TREE,
> false);
> +}
> +
> +/* A common subroutine for pop_cfun and pop_function_decl. FORCE is as
> + for set_function_decl. */
> +
> +static void
> +pop_cfun_1 (bool force)
> {
> struct function *new_cfun = cfun_stack.pop ();
> /* When in_dummy_function, we do have a cfun but current_function_decl is
> @@ -4750,10 +4784,30 @@ pop_cfun (void)
> gcc_checking_assert (in_dummy_function
> || !cfun
> || current_function_decl == cfun->decl);
> - set_cfun (new_cfun);
> + set_cfun (new_cfun, force);
> current_function_decl = new_cfun ? new_cfun->decl : NULL_TREE;
> }
>
> +/* Pop cfun from the stack. Also set current_function_decl accordingly. */
> +
> +void
> +pop_cfun (void)
> +{
> + pop_cfun_1 (false);
> +}
> +
> +/* Undo push_function_decl. */
> +
> +void
> +pop_function_decl (void)
> +{
> + /* If the previous cfun was null, the options should be reset to the
> + global set. Checking the current cfun against the new (popped) cfun
> + wouldn't catch this if the current function decl has no function
> + struct. */
> + pop_cfun_1 (!cfun_stack.last ());
> +}
> +
> /* Return value of funcdef and increase it. */
> int
> get_next_funcdef_no (void)
> diff --git a/gcc/function.h b/gcc/function.h
> index 243f5dd1b8c..92ba93c3f70 100644
> --- a/gcc/function.h
> +++ b/gcc/function.h
> @@ -701,6 +701,8 @@ extern void number_blocks (tree);
> extern void set_cfun (struct function *new_cfun, bool force = false);
> extern void push_cfun (struct function *new_cfun);
> extern void pop_cfun (void);
> +extern void push_function_decl (tree, bool = false);
> +extern void pop_function_decl (void);
>
> extern int get_next_funcdef_no (void);
> extern int get_last_funcdef_no (void);
>
--
Richard Biener <[email protected]>
SUSE Software Solutions Germany GmbH,
Frankenstrasse 146, 90461 Nuernberg, Germany;
GF: Ivo Totev, Andrew McDonald, Werner Knoblich; (HRB 36809, AG Nuernberg)
