> On Wed, Nov 12, 2014 at 02:49:30PM +0400, Maxim Ostapenko wrote:
> > We used this code for IPA propagation of nonfreeing_call_p. It implemented
> > with a separate pass, but it probably could be propagated in some existing
> > one. This analysis doesn't seem to be costly thought, we didn't see any
> > significant slowdown compiling big files.
>
> Here it is rewritten using ipa-pure-const which is where Richard/Honza
> suggested it should be done in.
>
> I wonder if the nonfreeing_call_p function shouldn't be moved elsewhere
> though (suggestion where), so that gimple.c doesn't need the cgraph
> includes.
>
> In any case, bootstrapped/regtested on x86_64-linux and i686-linux.
>
> 2014-11-12 Jakub Jelinek <[email protected]>
>
> * ipa-pure-const.c (struct funct_state_d): Add can_free field.
> (varying_state): Add true for can_free.
> (check_call): For builtin or internal !nonfreeing_call_p set
> local->can_free.
> (check_stmt): For asm volatile and asm with "memory" set
> local->can_free.
> (analyze_function): Clear local->can_free initially, continue
> calling check_stmt until all flags are computed, dump can_free
> flag.
> (pure_const_write_summary): Write can_free flag.
> (pure_const_read_summary): Read it back.
> (propagate_can_free): New function.
> (pass_ipa_pure_const::execute): Call it.
> * cgraph.h (cgraph_node): Add nonfreeing_fn member.
> * gimple.c: Include ipa-ref.h, lto-streamer.h and cgraph.h.
> (nonfreeing_call_p): Return cgraph nonfreeing_fn flag if set.
> * cgraph.c (cgraph_node::dump): Dump nonfreeing_fn flag.
> * lto-cgraph.c (lto_output_node): Write nonfreeing_fn flag.
> (input_overwrite_node): Read it back.
>
> --- gcc/ipa-pure-const.c.jj 2014-11-12 18:32:56.351139726 +0100
> +++ gcc/ipa-pure-const.c 2014-11-12 21:11:08.574354600 +0100
> @@ -112,11 +112,15 @@ struct funct_state_d
> bool looping;
>
> bool can_throw;
> +
> + /* If function can call free, munmap or otherwise make previously
> + non-trapping memory accesses trapping. */
> + bool can_free;
> };
>
> /* State used when we know nothing about function. */
> static struct funct_state_d varying_state
> - = { IPA_NEITHER, IPA_NEITHER, true, true, true };
> + = { IPA_NEITHER, IPA_NEITHER, true, true, true, true };
>
>
> typedef struct funct_state_d * funct_state;
> @@ -559,6 +563,10 @@ check_call (funct_state local, gimple ca
> enum pure_const_state_e call_state;
> bool call_looping;
>
> + if (gimple_call_builtin_p (call, BUILT_IN_NORMAL)
> + && !nonfreeing_call_p (call))
> + local->can_free = true;
> +
> if (special_builtin_state (&call_state, &call_looping, callee_t))
> {
> worse_state (&local->pure_const_state, &local->looping,
> @@ -589,6 +597,8 @@ check_call (funct_state local, gimple ca
> break;
> }
> }
> + else if (gimple_call_internal_p (call) && !nonfreeing_call_p (call))
> + local->can_free = true;
Actually I think you want to do this for can_throw, too.
We probably do not have throwing internal calls, but it is better to be safe.
> +/* Produce transitive closure over the callgraph and compute can_free
> + attributes. */
> +
> +static void
> +propagate_can_free (void)
> +{
> + struct cgraph_node *node;
> + struct cgraph_node *w;
> + struct cgraph_node **order
> + = XCNEWVEC (struct cgraph_node *, symtab->cgraph_count);
> + int order_pos;
> + int i;
> + struct ipa_dfs_info *w_info;
> +
> + order_pos = ipa_reduced_postorder (order, true, false, NULL);
> + if (dump_file)
> + {
> + cgraph_node::dump_cgraph (dump_file);
> + ipa_print_order (dump_file, "reduced", order, order_pos);
> + }
The propagation seems fine, but I wonder if we won't get better memory locality
doing this
during the propagation of pure/const?
nothrow flag goes in separate loop because knowledge of nothrow helps
pure/const to work better.
Also one can ignore call edges that are !can_thros_externally to get fewer
cycles, but apparently
this got never implemented.
> && gimple_call_flags (call) & ECF_LEAF)
> return true;
>
> - return false;
> + tree fndecl = gimple_call_fndecl (call);
> + if (!fndecl)
> + return false;
> + struct cgraph_node *n = cgraph_node::get (fndecl);
You want to walk aliases,
cgraph_node::get (fndecl)->function_symbol (&availability)
> + if (!n || n->get_availability () <= AVAIL_INTERPOSABLE)
and use availability here.
OK with this change.
Honza
