On Mon, 1 Nov 2021, Jan Hubicka wrote:
> Hi,
> this patch adds EAF_NOT_RETURNED_DIRECTLY which works similarly as
> EAF_NODIRECTESCAPE. Values pointed to by a given argument may be returned but
> not the argument itself. This helps PTA quite noticeably because we mostly
> care about tracking points to which given memory location can escape.
>
> I think this is about last reasonable improvement we can get to EAF
> flags.
>
> cc1plus disambiguation counts change from:
>
> Alias oracle query stats:
> refs_may_alias_p: 77976088 disambiguations, 98744590 queries
> ref_maybe_used_by_call_p: 572845 disambiguations, 79014622 queries
> call_may_clobber_ref_p: 340823 disambiguations, 344823 queries
> nonoverlapping_component_refs_p: 0 disambiguations, 26590 queries
> nonoverlapping_refs_since_match_p: 31626 disambiguations, 65379 must
> overlaps, 97963 queries
> aliasing_component_refs_p: 57414 disambiguations, 11434878 queries
> TBAA oracle: 27749649 disambiguations 91624184 queries
> 14733408 are in alias set 0
> 8847139 queries asked about the same object
> 139 queries asked about the same alias set
> 0 access volatile
> 38412201 are dependent in the DAG
> 1881648 are aritificially in conflict with void *
>
> Modref stats:
> modref use: 23785 disambiguations, 702425 queries
> modref clobber: 2296391 disambiguations, 22690531 queries
> 5260226 tbaa queries (0.231825 per modref query)
> 731741 base compares (0.032249 per modref query)
>
> PTA query stats:
> pt_solution_includes: 12580233 disambiguations, 35854408 queries
> pt_solutions_intersect: 1409041 disambiguations, 13496899 queries
>
> To:
>
> Alias oracle query stats:
> refs_may_alias_p: 78304485 disambiguations, 98830913 queries
> ref_maybe_used_by_call_p: 630360 disambiguations, 79308222 queries
> call_may_clobber_ref_p: 381549 disambiguations, 384627 queries
> nonoverlapping_component_refs_p: 0 disambiguations, 26299 queries
> nonoverlapping_refs_since_match_p: 29919 disambiguations, 64917 must
> overlaps, 95781 queries
> aliasing_component_refs_p: 57250 disambiguations, 11336880 queries
> TBAA oracle: 27835747 disambiguations 91534430 queries
> 14884868 are in alias set 0
> 8933627 queries asked about the same object
> 123 queries asked about the same alias set
> 0 access volatile
> 37974723 are dependent in the DAG
> 1905342 are aritificially in conflict with void *
>
> Modref stats:
> modref use: 24929 disambiguations, 756294 queries
> modref clobber: 2334910 disambiguations, 23414495 queries
> 5359212 tbaa queries (0.228884 per modref query)
> 754642 base compares (0.032230 per modref query)
>
> PTA query stats:
> pt_solution_includes: 13262256 disambiguations, 36306509 queries
> pt_solutions_intersect: 1574672 disambiguations, 13638933 queries
>
> So about 5% more pt_solution_includes and 11% more pt_solutions_intersect
> disambiguations.
>
> Bootstrapped/regtested x86_64-linux, OK?
OK.
Thanks,
Richard.
> Honza
>
> gcc/ChangeLog:
>
> * tree-core.h (EAF_NOT_RETURNED_DIRECTLY): New flag.
> (EAF_NOREAD): Renumber.
> * ipa-modref.c (dump_eaf_flags): Dump EAF_NOT_RETURNED_DIRECTLY.
> (remove_useless_eaf_flags): Handle EAF_NOT_RETURNED_DIRECTLY
> (deref_flags): Likewise.
> (modref_lattice::init): Likewise.
> (modref_lattice::merge): Likewise.
> (merge_call_lhs_flags): Likewise.
> (analyze_ssa_name_flags): Likewise.
> (modref_merge_call_site_flags): Likewise.
> * tree-ssa-structalias.c (handle_call_arg): Likewise.
>
> gcc/testsuite/ChangeLog:
>
> * gcc.dg/ipa/modref-3.c: New test.
> * gcc.dg/tree-ssa/modref-10.c: New test.
>
> diff --git a/gcc/ipa-modref.c b/gcc/ipa-modref.c
> index d866d9ed6b3..c0aae084dbd 100644
> --- a/gcc/ipa-modref.c
> +++ b/gcc/ipa-modref.c
> @@ -160,6 +160,8 @@ dump_eaf_flags (FILE *out, int flags, bool newline = true)
> fprintf (out, " unused");
> if (flags & EAF_NOT_RETURNED)
> fprintf (out, " not_returned");
> + if (flags & EAF_NOT_RETURNED_DIRECTLY)
> + fprintf (out, " not_returned_directly");
> if (flags & EAF_NOREAD)
> fprintf (out, " noread");
> if (newline)
> @@ -295,7 +297,7 @@ remove_useless_eaf_flags (int eaf_flags, int ecf_flags,
> bool returns_void)
> else if (ecf_flags & ECF_PURE)
> eaf_flags &= ~implicit_pure_eaf_flags;
> else if ((ecf_flags & ECF_NORETURN) || returns_void)
> - eaf_flags &= ~EAF_NOT_RETURNED;
> + eaf_flags &= ~(EAF_NOT_RETURNED | EAF_NOT_RETURNED_DIRECTLY);
> return eaf_flags;
> }
>
> @@ -1373,7 +1375,7 @@ memory_access_to (tree op, tree ssa_name)
> static int
> deref_flags (int flags, bool ignore_stores)
> {
> - int ret = EAF_NODIRECTESCAPE;
> + int ret = EAF_NODIRECTESCAPE | EAF_NOT_RETURNED_DIRECTLY;
> /* If argument is unused just account for
> the read involved in dereference. */
> if (flags & EAF_UNUSED)
> @@ -1458,7 +1460,8 @@ modref_lattice::init ()
> {
> /* All flags we track. */
> int f = EAF_DIRECT | EAF_NOCLOBBER | EAF_NOESCAPE | EAF_UNUSED
> - | EAF_NODIRECTESCAPE | EAF_NOT_RETURNED | EAF_NOREAD;
> + | EAF_NODIRECTESCAPE | EAF_NOT_RETURNED |
> + EAF_NOT_RETURNED_DIRECTLY | EAF_NOREAD;
> flags = f;
> /* Check that eaf_flags_t is wide enough to hold all flags. */
> gcc_checking_assert (f == flags);
> @@ -1540,6 +1543,8 @@ modref_lattice::merge (int f)
> Fnspec machinery does set both so compensate for this. */
> if (f & EAF_NOESCAPE)
> f |= EAF_NODIRECTESCAPE;
> + if (f & EAF_NOT_RETURNED)
> + f |= EAF_NOT_RETURNED_DIRECTLY;
> if ((flags & f) != flags)
> {
> flags &= f;
> @@ -1647,7 +1652,9 @@ merge_call_lhs_flags (gcall *call, int arg, int index,
> bool deref,
> && (flags & ERF_RETURN_ARG_MASK) != arg)
> return;
>
> - if (gimple_call_arg_flags (call, arg) & (EAF_NOT_RETURNED | EAF_UNUSED))
> + int eaf_flags = gimple_call_arg_flags (call, arg);
> +
> + if (eaf_flags & (EAF_NOT_RETURNED | EAF_UNUSED))
> return;
>
> /* If return value is SSA name determine its flags. */
> @@ -1655,12 +1662,14 @@ merge_call_lhs_flags (gcall *call, int arg, int
> index, bool deref,
> {
> tree lhs = gimple_call_lhs (call);
> analyze_ssa_name_flags (lhs, lattice, depth + 1, ipa);
> - if (deref)
> + if (deref || (eaf_flags & EAF_NOT_RETURNED_DIRECTLY))
> lattice[index].merge_deref (lattice[SSA_NAME_VERSION (lhs)], false);
> else
> lattice[index].merge (lattice[SSA_NAME_VERSION (lhs)]);
> }
> /* In the case of memory store we can do nothing. */
> + else if (eaf_flags & EAF_NOT_RETURNED_DIRECTLY)
> + lattice[index].merge (deref_flags (0, false));
> else
> lattice[index].merge (0);
> }
> @@ -1731,11 +1740,13 @@ analyze_ssa_name_flags (tree name,
> vec<modref_lattice> &lattice, int depth,
> && DECL_BY_REFERENCE (DECL_RESULT (current_function_decl)))
> ;
> else if (gimple_return_retval (ret) == name)
> - lattice[index].merge (~(EAF_UNUSED | EAF_NOT_RETURNED));
> + lattice[index].merge (~(EAF_UNUSED | EAF_NOT_RETURNED
> + | EAF_NOT_RETURNED_DIRECTLY));
> else if (memory_access_to (gimple_return_retval (ret), name))
> {
> lattice[index].merge_direct_load ();
> - lattice[index].merge (~(EAF_UNUSED | EAF_NOT_RETURNED));
> + lattice[index].merge (~(EAF_UNUSED | EAF_NOT_RETURNED
> + | EAF_NOT_RETURNED_DIRECTLY));
> }
> }
> /* Account for LHS store, arg loads and flags from callee function. */
> @@ -1794,7 +1805,8 @@ analyze_ssa_name_flags (tree name, vec<modref_lattice>
> &lattice, int depth,
> if (!(ecf_flags & (ECF_CONST | ECF_NOVOPS)))
> {
> int call_flags = gimple_call_arg_flags (call, i)
> - | EAF_NOT_RETURNED;
> + | EAF_NOT_RETURNED
> + | EAF_NOT_RETURNED_DIRECTLY;
> if (ignore_stores)
> call_flags |= ignore_stores_eaf_flags;
>
> @@ -1817,7 +1829,8 @@ analyze_ssa_name_flags (tree name, vec<modref_lattice>
> &lattice, int depth,
> {
> int call_flags = deref_flags
> (gimple_call_arg_flags (call, i)
> - | EAF_NOT_RETURNED, ignore_stores);
> + | EAF_NOT_RETURNED
> + | EAF_NOT_RETURNED_DIRECTLY, ignore_stores);
> if (!record_ipa)
> lattice[index].merge (call_flags);
> else
> @@ -3858,14 +3871,18 @@ modref_merge_call_site_flags (escape_summary *sum,
> flags_lto |= ignore_stores_eaf_flags;
> }
> /* Returning the value is already accounted to at local propagation.
> */
> - flags |= ee->min_flags | EAF_NOT_RETURNED;
> - flags_lto |= ee->min_flags | EAF_NOT_RETURNED;
> + flags |= ee->min_flags | EAF_NOT_RETURNED | EAF_NOT_RETURNED_DIRECTLY;
> + flags_lto |= ee->min_flags | EAF_NOT_RETURNED |
> EAF_NOT_RETURNED_DIRECTLY;
> /* Noescape implies that value also does not escape directly.
> Fnspec machinery does set both so compensate for this. */
> if (flags & EAF_NOESCAPE)
> flags |= EAF_NODIRECTESCAPE;
> if (flags_lto & EAF_NOESCAPE)
> flags_lto |= EAF_NODIRECTESCAPE;
> + if (flags & EAF_NOT_RETURNED)
> + flags |= EAF_NOT_RETURNED_DIRECTLY;
> + if (flags_lto & EAF_NOT_RETURNED)
> + flags_lto |= EAF_NOT_RETURNED_DIRECTLY;
> if (!(flags & EAF_UNUSED)
> && cur_summary && ee->parm_index < (int)cur_summary->arg_flags.length
> ())
> {
> diff --git a/gcc/testsuite/gcc.dg/ipa/modref-3.c
> b/gcc/testsuite/gcc.dg/ipa/modref-3.c
> new file mode 100644
> index 00000000000..c90683bc962
> --- /dev/null
> +++ b/gcc/testsuite/gcc.dg/ipa/modref-3.c
> @@ -0,0 +1,20 @@
> +/* { dg-options "-O2 -fdump-ipa-modref" } */
> +/* { dg-do link } */
> +int *ptr;
> +void linker_error ();
> +int
> +main ()
> +{
> + int a;
> + __attribute__((noinline)) int test2 ()
> + {
> + ptr = 0;
> + return a;
> + }
> + a = 1;
> + test2 ();
> + if (a != 1)
> + linker_error ();
> + return 0;
> +}
> +/* { dg-final { scan-ipa-dump "Static chain flags: noclobber noescape
> nodirectescape" "modref" } */
> diff --git a/gcc/testsuite/gcc.dg/tree-ssa/modref-10.c
> b/gcc/testsuite/gcc.dg/tree-ssa/modref-10.c
> new file mode 100644
> index 00000000000..c608408809d
> --- /dev/null
> +++ b/gcc/testsuite/gcc.dg/tree-ssa/modref-10.c
> @@ -0,0 +1,20 @@
> +/* { dg-do link } */
> +/* { dg-options "-O2 -fdump-tree-modref1" } */
> +void linker_error ();
> +__attribute__((noinline))
> +int *
> +test (int **a)
> +{
> + return *a;
> +}
> +int
> +main()
> +{
> + int val;
> + int *a=&val;
> + int *b = test (&a);
> + if (b == (int *)&a)
> + linker_error ();
> + return 0;
> +}
> +/* { dg-final { scan-tree-dump "parm 0 flags: noclobber noescape
> nodirectescape not_returned_directly" "modref1"} } */
> diff --git a/gcc/tree-core.h b/gcc/tree-core.h
> index d3d2a8d812f..8a55db2b3f5 100644
> --- a/gcc/tree-core.h
> +++ b/gcc/tree-core.h
> @@ -117,8 +117,12 @@ struct die_struct;
> /* Nonzero if the argument does not escape to return value. */
> #define EAF_NOT_RETURNED (1 << 5)
>
> +/* Nonzero if the argument argument itself does not escape
> + to return value but memory referenced by it may escape. */
> +#define EAF_NOT_RETURNED_DIRECTLY (1 << 6)
> +
> /* Nonzero if the argument is not read. */
> -#define EAF_NOREAD (1 << 6)
> +#define EAF_NOREAD (1 << 7)
>
> /* Call return flags. */
> /* Mask for the argument number that is returned. Lower two bits of
> diff --git a/gcc/tree-ssa-structalias.c b/gcc/tree-ssa-structalias.c
> index 99072df0768..5f24c0171f0 100644
> --- a/gcc/tree-ssa-structalias.c
> +++ b/gcc/tree-ssa-structalias.c
> @@ -4082,8 +4082,16 @@ handle_call_arg (gcall *stmt, tree arg, vec<ce_s>
> *results, int flags,
> {
> struct constraint_expr cexpr;
> cexpr.var = tem->id;
> - cexpr.type = SCALAR;
> - cexpr.offset = 0;
> + if (flags & EAF_NOT_RETURNED_DIRECTLY)
> + {
> + cexpr.type = DEREF;
> + cexpr.offset = UNKNOWN_OFFSET;
> + }
> + else
> + {
> + cexpr.type = SCALAR;
> + cexpr.offset = 0;
> + }
> results->safe_push (cexpr);
> }
>
>
--
Richard Biener <rguent...@suse.de>
SUSE Software Solutions Germany GmbH, Maxfeldstrasse 5, 90409 Nuernberg,
Germany; GF: Ivo Totev; HRB 36809 (AG Nuernberg)
