On Tue, 27 Oct 2020, Patrick Palka wrote:
> The adoption of P2104 means we can memoize the result of satisfaction
> indefinitely and no longer have to clear the satisfaction caches on
> various events that would affect satisfaction. To that end, this patch
> removes clear_satisfaction_cache and adjusts its callers appropriately.
>
> This provides a massive reduction in compile time and memory use in some
> cases. For example, on the libstdc++ test std/ranges/adaptor/join.cc,
> compile time and memory usage drops nearly 75%, from 7.5s/770MB to
> 2s/230MB, with a --enable-checking=release compiler.
>
> [ This patch depends on
>
> c++: Check constraints only for candidate conversion functions.
>
> Without it, many of the libstdc++ range adaptor tests fail due to
> us now indefinitely memoizing a bogus satisfaction result caused by
> checking the constraints of a conversion function when we weren't
> supposed to, which led to a "use of foo_view::end() before deduction
> of auto" SFINAE error. This went unnoticed without this patch because
> by the time we needed this satisfaction result again, we had cleared
> the satisfaction cache and finished deducing the return type of
> foo_view::end(), so on subsequent tries we computed the correct
> satisfaction result. ]
With the library-side workaround r11-4584 for the range adaptor test
failures now committed, the mentioned frontend patch about candidate
conversion functions is no longer a prerequisite (and was not we want
anyway).
>
> Bootstrapped and regtested on x86_64-pc-linux-gnu, does this look OK for
> trunk (pending approval of the prerequisite patch)? Also tested on
> cmcstl2 and range-v3.
Now successfully bootstrapped and regtested on top of r11-4584, and also
tested on cmcstl2 and range-v3. Does this look OK for trunk?
>
> gcc/cp/ChangeLog:
>
> * class.c (finish_struct_1): Don't call clear_satisfaction_cache.
> * constexpr.c (clear_cv_and_fold_caches): Likewise. Remove bool
> parameter.
> * constraint.cc (clear_satisfaction_cache): Remove definition.
> * cp-tree.h (clear_satisfaction_cache): Remove declaration.
> (clear_cv_and_fold_caches): Remove bool parameter.
> * typeck2.c (store_init_value): Remove argument to
> clear_cv_and_fold_caches.
>
> gcc/testsuite/ChangeLog:
>
> * g++.dg/cpp2a/concept-complete1.C: Delete ill-formed test.
> ---
> gcc/cp/class.c | 3 ---
> gcc/cp/constexpr.c | 6 ++----
> gcc/cp/constraint.cc | 9 ---------
> gcc/cp/cp-tree.h | 3 +--
> gcc/cp/typeck2.c | 2 +-
> gcc/testsuite/g++.dg/cpp2a/concepts-complete1.C | 11 -----------
> 6 files changed, 4 insertions(+), 30 deletions(-)
> delete mode 100644 gcc/testsuite/g++.dg/cpp2a/concepts-complete1.C
>
> diff --git a/gcc/cp/class.c b/gcc/cp/class.c
> index 26f996b7f4b..6c21682a3e5 100644
> --- a/gcc/cp/class.c
> +++ b/gcc/cp/class.c
> @@ -7472,9 +7472,6 @@ finish_struct_1 (tree t)
> /* Finish debugging output for this type. */
> rest_of_type_compilation (t, ! LOCAL_CLASS_P (t));
>
> - /* Recalculate satisfaction that might depend on completeness. */
> - clear_satisfaction_cache ();
> -
> if (TYPE_TRANSPARENT_AGGR (t))
> {
> tree field = first_field (t);
> diff --git a/gcc/cp/constexpr.c b/gcc/cp/constexpr.c
> index 7ebdd308dcd..ec60db4a44b 100644
> --- a/gcc/cp/constexpr.c
> +++ b/gcc/cp/constexpr.c
> @@ -7085,15 +7085,13 @@ clear_cv_cache (void)
> cv_cache->empty ();
> }
>
> -/* Dispose of the whole CV_CACHE, FOLD_CACHE, and satisfaction caches. */
> +/* Dispose of the whole CV_CACHE and FOLD_CACHE. */
>
> void
> -clear_cv_and_fold_caches (bool sat /*= true*/)
> +clear_cv_and_fold_caches ()
> {
> clear_cv_cache ();
> clear_fold_cache ();
> - if (sat)
> - clear_satisfaction_cache ();
> }
>
> /* Internal function handling expressions in templates for
> diff --git a/gcc/cp/constraint.cc b/gcc/cp/constraint.cc
> index 75457a2dd60..8c0111a6409 100644
> --- a/gcc/cp/constraint.cc
> +++ b/gcc/cp/constraint.cc
> @@ -2354,15 +2354,6 @@ save_satisfaction (tree constr, tree args, tree result)
> *slot = entry;
> }
>
> -void
> -clear_satisfaction_cache ()
> -{
> - if (sat_cache)
> - sat_cache->empty ();
> - if (decl_satisfied_cache)
> - decl_satisfied_cache->empty ();
> -}
> -
> /* A tool to help manage satisfaction caching in satisfy_constraint_r.
> Note the cache is only used when not diagnosing errors. */
>
> diff --git a/gcc/cp/cp-tree.h b/gcc/cp/cp-tree.h
> index 1ce20989e13..7a6efca6121 100644
> --- a/gcc/cp/cp-tree.h
> +++ b/gcc/cp/cp-tree.h
> @@ -7834,7 +7834,6 @@ extern tree evaluate_concept_check (tree,
> tsubst_flags_t);
> extern tree satisfy_constraint_expression (tree);
> extern bool constraints_satisfied_p (tree);
> extern bool constraints_satisfied_p (tree, tree);
> -extern void clear_satisfaction_cache ();
> extern bool* lookup_subsumption_result (tree, tree);
> extern bool save_subsumption_result (tree, tree, bool);
> extern tree find_template_parameters (tree, tree);
> @@ -7904,7 +7903,7 @@ extern bool var_in_maybe_constexpr_fn (tree);
> extern void explain_invalid_constexpr_fn (tree);
> extern vec<tree> cx_error_context (void);
> extern tree fold_sizeof_expr (tree);
> -extern void clear_cv_and_fold_caches (bool = true);
> +extern void clear_cv_and_fold_caches (void);
> extern tree unshare_constructor (tree
> CXX_MEM_STAT_INFO);
>
> /* An RAII sentinel used to restrict constexpr evaluation so that it
> diff --git a/gcc/cp/typeck2.c b/gcc/cp/typeck2.c
> index e259a4201be..445e2a211c8 100644
> --- a/gcc/cp/typeck2.c
> +++ b/gcc/cp/typeck2.c
> @@ -954,7 +954,7 @@ store_init_value (tree decl, tree init, vec<tree,
> va_gc>** cleanups, int flags)
> return split_nonconstant_init (decl, value);
>
> /* DECL may change value; purge caches. */
> - clear_cv_and_fold_caches (TREE_STATIC (decl));
> + clear_cv_and_fold_caches ();
>
> /* If the value is a constant, just put it in DECL_INITIAL. If DECL
> is an automatic variable, the middle end will turn this into a
> diff --git a/gcc/testsuite/g++.dg/cpp2a/concepts-complete1.C
> b/gcc/testsuite/g++.dg/cpp2a/concepts-complete1.C
> deleted file mode 100644
> index 63f36965f00..00000000000
> --- a/gcc/testsuite/g++.dg/cpp2a/concepts-complete1.C
> +++ /dev/null
> @@ -1,11 +0,0 @@
> -// { dg-do compile { target c++20 } }
> -
> -template <class T> concept has_mem_type = requires { typename T::type; };
> -
> -template <has_mem_type T> int f () { return 0; }
> -template <class T> char f() { return 0; }
> -
> -struct A;
> -static_assert (sizeof (f<A>()) == 1);
> -struct A { typedef int type; };
> -static_assert (sizeof (f<A>()) > 1);
> --
> 2.29.0.rc0
>
>
