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Diffstat (limited to 'gcc/lto-wpa-fixup.c')
| -rw-r--r-- | gcc/lto-wpa-fixup.c | 281 |
1 files changed, 281 insertions, 0 deletions
diff --git a/gcc/lto-wpa-fixup.c b/gcc/lto-wpa-fixup.c new file mode 100644 index 00000000000..4411588f2f3 --- /dev/null +++ b/gcc/lto-wpa-fixup.c @@ -0,0 +1,281 @@ +/* Write and read any fix-up information generated by the WPA mode. + + Copyright 2009 Free Software Foundation, Inc. + Contributed by Doug Kwan <dougkwan@google.com> + +This file is part of GCC. + +GCC is free software; you can redistribute it and/or modify it under +the terms of the GNU General Public License as published by the Free +Software Foundation; either version 3, or (at your option) any later +version. + +GCC is distributed in the hope that it will be useful, but WITHOUT ANY +WARRANTY; without even the implied warranty of MERCHANTABILITY or +FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License +for more details. + +You should have received a copy of the GNU General Public License +along with GCC; see the file COPYING3. If not see +<http://www.gnu.org/licenses/>. */ + +#include "config.h" +#include "system.h" +#include "coretypes.h" +#include "tm.h" +#include "toplev.h" +#include "tree.h" +#include "expr.h" +#include "flags.h" +#include "cgraph.h" +#include "function.h" +#include "diagnostic.h" +#include "vec.h" +#include "bitmap.h" +#include "timevar.h" +#include "tree-flow.h" +#include "tree-pass.h" +#include "lto-streamer.h" + +/* LTO fix-up. + + In WPA mode, LTO cannot access function bodies. Some modifications in + IR require additional updates in function bodies, which are not possible + in WPA mode. So we write out information about these modifications for + LTRANS to fix up the function bodies accordingly. */ + +/* The vectors records function DECLs having multiple copies with different + exception throwing attributes. We do not mark a DECL if all copies of it + have the same exception throwing attribute. */ +static bitmap lto_nothrow_fndecls; + +/* We need to fix up GIMPLE bodies due to changes in exception setting. + Consider this example: + + a.h: + class a { + public: + a(); + ~a(); + }; + + main.cc: + #include "a.h" + + int + main (int argc, char **argv) + { + a x; + return 0; + } + + a.cc: + #include "a.h" + a::a() {} + a::~a() {} + + When main.cc is compiled, gcc only sees the constructor declaration, so + the constructor and hence the call to it are marked as exception throwing. + When a.cc is compiled, the body of the constructor is available and is + obviously not exception throwing. Thus DECL of a::a in a.o has the NOTHROW + attribute. When LTO runs, two DECLs of a::a with different exception + attributes are merged. We want the merged DECL to be not exception + throwing for better generated code. To do that, we need to fix up any + function calls that have been marked as exception throwing. */ + +/* Fix up all the call statements whose target fndecls might have changed + to NOTHROW. Note that this problem is not WPA specific. We can also + run into this problem in normal LTO with multiple input files. */ + +void +lto_fixup_nothrow_decls (void) +{ + struct cgraph_node *node; + struct cgraph_edge *edge; + struct function *caller_function; + gimple call_stmt; + + /* Quit if we are in WPA mode or have not marked any DECLs. */ + if (flag_wpa || !lto_nothrow_fndecls) + return; + + /* For each node that has been marked, go over all call edges to it. */ + for (node = cgraph_nodes; node; node = node->next) + if (bitmap_bit_p (lto_nothrow_fndecls, DECL_UID (node->decl))) + { + gcc_assert (TREE_NOTHROW (node->decl)); + for (edge = node->callers; edge; edge = edge->next_caller) + { + caller_function = DECL_STRUCT_FUNCTION (edge->caller->decl); + call_stmt = edge->call_stmt; + gcc_assert (call_stmt); + if (lookup_stmt_eh_lp_fn (caller_function, call_stmt) != 0) + remove_stmt_from_eh_lp_fn (caller_function, call_stmt); + } + } +} + +/* Mark FNDECL as becoming not exception throwing. */ + +void +lto_mark_nothrow_fndecl (tree fndecl) +{ + gcc_assert (TREE_CODE (fndecl) == FUNCTION_DECL); + if (!lto_nothrow_fndecls) + lto_nothrow_fndecls = lto_bitmap_alloc (); + + bitmap_set_bit (lto_nothrow_fndecls, DECL_UID (fndecl)); +} + +/* Write out fix-up information. Currently the only WPA fix-up + information is the list of DECLs marked as not exception throwing. SET + is a cgraph node set whose fix-up information is to be written. */ + +static void +lto_output_wpa_fixup (cgraph_node_set set) +{ + struct lto_simple_output_block *ob; + cgraph_node_set_iterator csi; + tree fndecl; + bitmap seen_decls; + VEC(tree, heap) *decls = NULL; + unsigned HOST_WIDE_INT i, count; + + ob = lto_create_simple_output_block (LTO_section_wpa_fixup); + + /* Accumulate the DECLs to be written out. Since we do not want + duplicates, we need to use a bitmap and a vector to save the + DECLs we want. Note that we need to check if lto_nothrow_fndecls + is NULL. This happens when no DECL has been marked. */ + seen_decls = lto_bitmap_alloc (); + if (lto_nothrow_fndecls) + for (csi = csi_start (set); !csi_end_p (csi); csi_next (&csi)) + { + struct cgraph_edge *e; + struct cgraph_node *n; + + n = csi_node (csi); + fndecl = n->decl; + + /* Check if the N's function is in the set of nothrow functions. */ + if (!bitmap_bit_p (seen_decls, DECL_UID (fndecl))) + { + bitmap_set_bit (seen_decls, (DECL_UID (fndecl))); + if (bitmap_bit_p (lto_nothrow_fndecls, DECL_UID (fndecl))) + VEC_safe_push (tree, heap, decls, fndecl); + } + + /* Now check the callees and also add them if they are nothrow. This + is needed because node N may end up in a different partition than + its callees. In which case, when the file holding N is compiled, + the calls it makes to nothrow functions will not be fixed up, + causing verification issues. */ + for (e = n->callees; e; e = e->next_callee) + { + fndecl = e->callee->decl; + if (!bitmap_bit_p (seen_decls, DECL_UID (fndecl))) + { + bitmap_set_bit (seen_decls, (DECL_UID (fndecl))); + if (bitmap_bit_p (lto_nothrow_fndecls, DECL_UID (fndecl))) + VEC_safe_push (tree, heap, decls, fndecl); + } + } + } + + /* Write out number of DECLs, followed by the DECLs. */ + count = VEC_length (tree, decls); + lto_output_uleb128_stream (ob->main_stream, count); + for (i = 0; i < count; i++) + { + fndecl = VEC_index (tree, decls, i); + lto_output_fn_decl_index (ob->decl_state, ob->main_stream, fndecl); + } + + /* Release resources. */ + lto_destroy_simple_output_block (ob); + VEC_free(tree, heap, decls); + lto_bitmap_free (seen_decls); +} + +/* Read in WPA fix-up information from one file. FILE_DATA points to + DECL information of the file where as IB is the input block for the + WPA fix-up section. */ + +static void +lto_input_wpa_fixup_1 (struct lto_file_decl_data *file_data, + struct lto_input_block *ib) +{ + unsigned HOST_WIDE_INT i, count, decl_index; + tree fndecl; + + count = lto_input_uleb128 (ib); + for (i = 0; i < count; i++) + { + decl_index = lto_input_uleb128 (ib); + fndecl = lto_file_decl_data_get_fn_decl (file_data, decl_index); + lto_mark_nothrow_fndecl (fndecl); + } +} + +/* Read in WPA fix-up information. */ + +static void +lto_input_wpa_fixup (void) +{ + struct lto_file_decl_data ** file_data_vec + = lto_get_file_decl_data (); + struct lto_file_decl_data * file_data; + int i = 0; + + /* Fix up information is only used in LTRANS mode. */ + if (!flag_ltrans) + return; + + while ((file_data = file_data_vec[i++])) + { + const char *data; + size_t len; + struct lto_input_block *ib + = lto_create_simple_input_block (file_data, LTO_section_wpa_fixup, + &data, &len); + + lto_input_wpa_fixup_1 (file_data, ib); + lto_destroy_simple_input_block (file_data, LTO_section_wpa_fixup, ib, + data, len); + } +} + +/* Gate function for all lto streaming passes. */ + +static bool +gate_wpa_fixup (void) +{ + return (flag_wpa || flag_ltrans) && gate_lto_out (); +} + +struct ipa_opt_pass_d pass_ipa_lto_wpa_fixup = +{ + { + IPA_PASS, + "lto_wpa_fixup", /* name */ + gate_wpa_fixup, /* gate */ + NULL, /* execute */ + NULL, /* sub */ + NULL, /* next */ + 0, /* static_pass_number */ + TV_WHOPR_WPA_FIXUP, /* tv_id */ + 0, /* properties_required */ + 0, /* properties_provided */ + 0, /* properties_destroyed */ + 0, /* todo_flags_start */ + TODO_dump_func /* todo_flags_finish */ + }, + NULL, /* generate_summary */ + lto_output_wpa_fixup, /* write_summary */ + lto_input_wpa_fixup, /* read_summary */ + NULL, /* function_read_summary */ + 0, /* TODOs */ + NULL, /* function_transform */ + NULL /* variable_transform */ +}; + |