From b360d4aafc1356386313c7392f7444b3fc356681 Mon Sep 17 00:00:00 2001 From: Jason Merrill Date: Thu, 6 Mar 2025 12:39:36 -0500 Subject: [PATCH] c++/modules: purview of explicit instantiations [PR114630] When calling instantiate_pending_templates at end of parsing, any new functions that are instantiated from this point have their module purview set based on the current value of module_kind. This is unideal, however, as the modules code will then treat these instantiations as reachable and cause large swathes of the GMF to be emitted into the module CMI, despite no code in the actual module purview referencing it. This patch fixes this by setting DECL_MODULE_PURVIEW_P as appropriate when we see an explicit instantiation, and adjusting module_kind accordingly during deferred instantiation, meaning that GMF entities won't be counted as reachable unless referenced by an actually reachable entity. Note that purviewness and attachment etc. is generally only determined by the base template: this is purely for determining whether an explicit instantiation is in the module purview and hence whether it should be streamed out. See the comment on 'set_instantiating_module'. Incidentally, since the "xtreme" testcases are deliberately large (and this commit adds another one), let's make sure we only run them once. PR c++/114630 PR c++/114795 gcc/cp/ChangeLog: * pt.cc (reopen_tinst_level): Set or clear MK_PURVIEW. (mark_decl_instantiated): Call set_instantiating_module. (instantiate_pending_templates): Save and restore module_kind so it isn't affected by reopen_tinst_level. gcc/testsuite/ChangeLog: * g++.dg/modules/modules.exp: Run xtreme tests once. * g++.dg/modules/gmf-3.C: New test. * g++.dg/modules/gmf-4.C: New test. * g++.dg/modules/gmf-xtreme.C: New test. Signed-off-by: Nathaniel Shead Co-authored-by: Nathaniel Shead --- gcc/cp/pt.cc | 17 ++++++++++++- gcc/testsuite/g++.dg/modules/gmf-3.C | 29 +++++++++++++++++++++++ gcc/testsuite/g++.dg/modules/gmf-4.C | 13 ++++++++++ gcc/testsuite/g++.dg/modules/gmf-xtreme.C | 10 ++++++++ gcc/testsuite/g++.dg/modules/modules.exp | 12 ++++++---- 5 files changed, 76 insertions(+), 5 deletions(-) create mode 100644 gcc/testsuite/g++.dg/modules/gmf-3.C create mode 100644 gcc/testsuite/g++.dg/modules/gmf-4.C create mode 100644 gcc/testsuite/g++.dg/modules/gmf-xtreme.C diff --git a/gcc/cp/pt.cc b/gcc/cp/pt.cc index 2378f892a53..6ac9e6f163e 100644 --- a/gcc/cp/pt.cc +++ b/gcc/cp/pt.cc @@ -11476,7 +11476,19 @@ reopen_tinst_level (struct tinst_level *level) pop_tinst_level (); if (current_tinst_level) current_tinst_level->errors = errorcount+sorrycount; - return level->maybe_get_node (); + + tree decl = level->maybe_get_node (); + if (decl && modules_p ()) + { + /* An instantiation is in module purview only if it had an explicit + instantiation definition in module purview; mark_decl_instantiated uses + set_instantiating_module to set the flag in that case. */ + if (DECL_MODULE_PURVIEW_P (decl)) + module_kind |= MK_PURVIEW; + else + module_kind &= ~MK_PURVIEW; + } + return decl; } /* Returns the TINST_LEVEL which gives the original instantiation @@ -25969,6 +25981,7 @@ mark_decl_instantiated (tree result, int extern_p) { mark_definable (result); mark_needed (result); + set_instantiating_module (result); /* Always make artificials weak. */ if (DECL_ARTIFICIAL (result) && flag_weak) comdat_linkage (result); @@ -27930,6 +27943,7 @@ instantiate_pending_templates (int retries) { int reconsider; location_t saved_loc = input_location; + unsigned saved_module_kind = module_kind; /* Instantiating templates may trigger vtable generation. This in turn may require further template instantiations. We place a limit here @@ -28020,6 +28034,7 @@ instantiate_pending_templates (int retries) while (reconsider); input_location = saved_loc; + module_kind = saved_module_kind; } /* Substitute ARGVEC into T, which is a list of initializers for diff --git a/gcc/testsuite/g++.dg/modules/gmf-3.C b/gcc/testsuite/g++.dg/modules/gmf-3.C new file mode 100644 index 00000000000..6b7ed503669 --- /dev/null +++ b/gcc/testsuite/g++.dg/modules/gmf-3.C @@ -0,0 +1,29 @@ +// PR c++/114630 +// { dg-additional-options "-fmodules-ts -Wno-global-module -fdump-lang-module" } +// { dg-module-cmi M } + +module; +template struct allocator { + allocator() {} +}; +template class allocator; + +// Deferred instantiation of GM virtual functions or friend functions +// should not place newly discovered declarations in the module purview. +template +void go() { + extern T fn_decl(); +} +template +struct S { + friend void x() {} + virtual void f() { + go(); + } +}; +inline S s; + +export module M; + +// The whole GMF should be discarded here +// { dg-final { scan-lang-dump "Wrote 0 clusters" module } } diff --git a/gcc/testsuite/g++.dg/modules/gmf-4.C b/gcc/testsuite/g++.dg/modules/gmf-4.C new file mode 100644 index 00000000000..91368f3cdcc --- /dev/null +++ b/gcc/testsuite/g++.dg/modules/gmf-4.C @@ -0,0 +1,13 @@ +// PR c++/114630 +// { dg-additional-options "-fmodules-ts -Wno-global-module -fdump-lang-module" } +// { dg-module-cmi M } + +module; +template struct allocator { + allocator() {} +}; +export module M; +template class allocator; + +// allocator is reachable because the explicit instantiation is in purview. +// { dg-final { scan-lang-dump {Wrote declaration[^\n]*allocator} module } } diff --git a/gcc/testsuite/g++.dg/modules/gmf-xtreme.C b/gcc/testsuite/g++.dg/modules/gmf-xtreme.C new file mode 100644 index 00000000000..0a01c405291 --- /dev/null +++ b/gcc/testsuite/g++.dg/modules/gmf-xtreme.C @@ -0,0 +1,10 @@ +// PR c++/114630 +// { dg-additional-options "-fmodules-ts -fdump-lang-module" } +// { dg-module-cmi empty } + +module; +#include "xtreme-header.h" +export module empty; + +// The whole GMF should be discarded here +// { dg-final { scan-lang-dump "Wrote 0 clusters" module } } diff --git a/gcc/testsuite/g++.dg/modules/modules.exp b/gcc/testsuite/g++.dg/modules/modules.exp index 335401b2166..81d0bebdfe5 100644 --- a/gcc/testsuite/g++.dg/modules/modules.exp +++ b/gcc/testsuite/g++.dg/modules/modules.exp @@ -269,6 +269,7 @@ proc module-init { src } { set std_prefix "-std=c++" global extra_tool_flags set extra_tool_flags {} + global MOD_STD_LIST foreach op $tmp { switch [lindex $op 0] { @@ -288,13 +289,16 @@ proc module-init { src } { } } - if { !$have_std } { - global MOD_STD_LIST + if { $have_std } { + lappend option_list "" + } elseif { [string match "*xtreme*" $src] } { + # Only run the xtreme tests once. + set x [lindex $MOD_STD_LIST end] + lappend option_list "${std_prefix}$x" + } else { foreach x $MOD_STD_LIST { lappend option_list "${std_prefix}$x" } - } else { - lappend option_list "" } return $option_list