// icf.cc -- Identical Code Folding.
//
-// Copyright 2009 Free Software Foundation, Inc.
+// Copyright (C) 2009-2020 Free Software Foundation, Inc.
// Written by Sriraman Tallam <tmsriram@google.com>.
// This file is part of gold.
// Identical Code Folding Algorithm
// ----------------------------------
// Detecting identical functions is done here and the basic algorithm
-// is as follows. A checksum is computed on each .text section using
+// is as follows. A checksum is computed on each foldable section using
// its contents and relocations. If the symbol name corresponding to
// a relocation is known it is used to compute the checksum. If the
// symbol name is not known the stringified name of the object and the
// checking the contents when two sections have the same checksum.
//
// However, two functions A and B with identical text but with
-// relocations pointing to different .text sections can be identical if
-// the corresponding .text sections to which their relocations point to
+// relocations pointing to different foldable sections can be identical if
+// the corresponding foldable sections to which their relocations point to
// turn out to be identical. Hence, this checksumming process must be
// done repeatedly until convergence is obtained. Here is an example for
// the following case :
// when folding takes place. This could lead to unexpected run-time
// behaviour.
//
+// Safe Folding :
+// ------------
+//
+// ICF in safe mode folds only ctors and dtors if their function pointers can
+// never be taken. Also, for X86-64, safe folding uses the relocation
+// type to determine if a function's pointer is taken or not and only folds
+// functions whose pointers are definitely not taken.
+//
+// Caveat with safe folding :
+// ------------------------
+//
+// This applies only to x86_64.
+//
+// Position independent executables are created from PIC objects (compiled
+// with -fPIC) and/or PIE objects (compiled with -fPIE). For PIE objects, the
+// relocation types for function pointer taken and a call are the same.
+// Now, it is not always possible to tell if an object used in the link of
+// a pie executable is a PIC object or a PIE object. Hence, for pie
+// executables, using relocation types to disambiguate function pointers is
+// currently disabled.
+//
+// Further, it is not correct to use safe folding to build non-pie
+// executables using PIC/PIE objects. PIC/PIE objects have different
+// relocation types for function pointers than non-PIC objects, and the
+// current implementation of safe folding does not handle those relocation
+// types. Hence, if used, functions whose pointers are taken could still be
+// folded causing unpredictable run-time behaviour if the pointers were used
+// in comparisons.
+//
+// Notes regarding C++ exception handling :
+// --------------------------------------
+//
+// It is possible for two sections to have identical text, identical
+// relocations, but different exception handling metadata (unwind
+// information in the .eh_frame section, and/or handler information in
+// a .gcc_except_table section). Thus, if a foldable section is
+// referenced from a .eh_frame FDE, we must include in its checksum
+// the contents of that FDE as well as of the CIE that the FDE refers
+// to. The CIE and FDE in turn probably contain relocations to the
+// personality routine and LSDA, which are handled like any other
+// relocation for ICF purposes. This logic is helped by the fact that
+// gcc with -ffunction-sections puts each function's LSDA in its own
+// .gcc_except_table.<functionname> section. Given sections for two
+// functions with nontrivial exception handling logic, we will
+// determine on the first iteration that their .gcc_except_table
+// sections are identical and can be folded, and on the second
+// iteration that their .text and .eh_frame contents (including the
+// now-merged .gcc_except_table relocations for the LSDA) are
+// identical and can be folded.
//
-// How to run : --icf
+//
+// How to run : --icf=[safe|all|none]
// Optional parameters : --icf-iterations <num> --print-icf-sections
//
// Performance : Less than 20 % link-time overhead on industry strength
#include "icf.h"
#include "symtab.h"
#include "libiberty.h"
+#include "demangle.h"
+#include "elfcpp.h"
+#include "int_encoding.h"
+
+#include <limits>
namespace gold
{
section_size_type plen;
if (section_contents == NULL)
{
+ // Lock the object so we can read from it. This is only called
+ // single-threaded from queue_middle_tasks, so it is OK to lock.
+ // Unfortunately we have no way to pass in a Task token.
+ const Task* dummy_task = reinterpret_cast<const Task*>(-1);
+ Task_lock_obj<Object> tl(dummy_task, secn.first);
const unsigned char* contents;
contents = secn.first->section_contents(secn.second,
&plen,
}
}
+// For SHF_MERGE sections that use REL relocations, the addend is stored in
+// the text section at the relocation offset. Read the addend value given
+// the pointer to the addend in the text section and the addend size.
+// Update the addend value if a valid addend is found.
+// Parameters:
+// RELOC_ADDEND_PTR : Pointer to the addend in the text section.
+// ADDEND_SIZE : The size of the addend.
+// RELOC_ADDEND_VALUE : Pointer to the addend that is updated.
+
+inline void
+get_rel_addend(const unsigned char* reloc_addend_ptr,
+ const unsigned int addend_size,
+ uint64_t* reloc_addend_value)
+{
+ switch (addend_size)
+ {
+ case 0:
+ break;
+ case 1:
+ *reloc_addend_value =
+ read_from_pointer<8>(reloc_addend_ptr);
+ break;
+ case 2:
+ *reloc_addend_value =
+ read_from_pointer<16>(reloc_addend_ptr);
+ break;
+ case 4:
+ *reloc_addend_value =
+ read_from_pointer<32>(reloc_addend_ptr);
+ break;
+ case 8:
+ *reloc_addend_value =
+ read_from_pointer<64>(reloc_addend_ptr);
+ break;
+ default:
+ gold_unreachable();
+ }
+}
+
// This returns the buffer containing the section's contents, both
// text and relocs. Relocs are differentiated as those pointing to
// sections that could be folded and those that cannot. Only relocs
// subsequent invocations of this function.
// Parameters :
// FIRST_ITERATION : true if it is the first invocation.
+// FIXED_CACHE : String that stores the portion of the result that
+// does not change from iteration to iteration;
+// written if first_iteration is true, read if it's false.
// SECN : Section for which contents are desired.
-// SECTION_NUM : Unique section number of this section.
+// SELF_SECN : Relocations that target this section will be
+// considered "relocations to self" so that recursive
+// functions can be folded. Should normally be the
+// same as `secn` except when processing extra identity
+// regions.
// NUM_TRACKED_RELOCS : Vector reference to store the number of relocs
// to ICF sections.
// KEPT_SECTION_ID : Vector which maps folded sections to kept sections.
-// SECTION_CONTENTS : Store the section's text and relocs to non-ICF
-// sections.
+// START_OFFSET : Only consider the part of the section at and after
+// this offset.
+// END_OFFSET : Only consider the part of the section before this
+// offset.
static std::string
get_section_contents(bool first_iteration,
+ std::string* fixed_cache,
const Section_id& secn,
- unsigned int section_num,
+ const Section_id& self_secn,
unsigned int* num_tracked_relocs,
Symbol_table* symtab,
const std::vector<unsigned int>& kept_section_id,
- std::vector<std::string>* section_contents)
+ section_offset_type start_offset = 0,
+ section_offset_type end_offset =
+ std::numeric_limits<section_offset_type>::max())
{
section_size_type plen;
const unsigned char* contents = NULL;
-
if (first_iteration)
- {
- contents = secn.first->section_contents(secn.second,
- &plen,
- false);
- }
+ contents = secn.first->section_contents(secn.second, &plen, false);
// The buffer to hold all the contents including relocs. A checksum
// is then computed on this buffer.
std::string buffer;
std::string icf_reloc_buffer;
- if (num_tracked_relocs)
- *num_tracked_relocs = 0;
+ Icf::Reloc_info_list& reloc_info_list =
+ symtab->icf()->reloc_info_list();
- Icf::Section_list& seclist = symtab->icf()->section_reloc_list();
- Icf::Symbol_list& symlist = symtab->icf()->symbol_reloc_list();
- Icf::Addend_list& addendlist = symtab->icf()->addend_reloc_list();
-
- Icf::Section_list::iterator it_seclist = seclist.find(secn);
- Icf::Symbol_list::iterator it_symlist = symlist.find(secn);
- Icf::Addend_list::iterator it_addendlist = addendlist.find(secn);
+ Icf::Reloc_info_list::iterator it_reloc_info_list =
+ reloc_info_list.find(secn);
buffer.clear();
icf_reloc_buffer.clear();
// Process relocs and put them into the buffer.
- if (it_seclist != seclist.end())
+ if (it_reloc_info_list != reloc_info_list.end())
{
- gold_assert(it_symlist != symlist.end());
- gold_assert(it_addendlist != addendlist.end());
- Icf::Sections_reachable_list v = it_seclist->second;
- Icf::Symbol_info s = it_symlist->second;
- Icf::Addend_info a = it_addendlist->second;
- Icf::Sections_reachable_list::iterator it_v = v.begin();
- Icf::Symbol_info::iterator it_s = s.begin();
+ Icf::Sections_reachable_info &v =
+ (it_reloc_info_list->second).section_info;
+ // Stores the information of the symbol pointed to by the reloc.
+ const Icf::Symbol_info &s = (it_reloc_info_list->second).symbol_info;
+ // Stores the addend and the symbol value.
+ Icf::Addend_info &a = (it_reloc_info_list->second).addend_info;
+ // Stores the offset of the reloc.
+ const Icf::Offset_info &o = (it_reloc_info_list->second).offset_info;
+ const Icf::Reloc_addend_size_info &reloc_addend_size_info =
+ (it_reloc_info_list->second).reloc_addend_size_info;
+ Icf::Sections_reachable_info::iterator it_v = v.begin();
+ Icf::Symbol_info::const_iterator it_s = s.begin();
Icf::Addend_info::iterator it_a = a.begin();
+ Icf::Offset_info::const_iterator it_o = o.begin();
+ Icf::Reloc_addend_size_info::const_iterator it_addend_size =
+ reloc_addend_size_info.begin();
- for (; it_v != v.end(); ++it_v, ++it_s, ++it_a)
+ for (; it_v != v.end(); ++it_v, ++it_s, ++it_a, ++it_o, ++it_addend_size)
{
- // ADDEND_STR stores the symbol value and addend, each
- // atmost 16 hex digits long. it_v points to a pair
+ Symbol* gsym = *it_s;
+ bool is_section_symbol = false;
+
+ // Ignore relocations outside the region we were told to look at
+ if (static_cast<section_offset_type>(*it_o) < start_offset
+ || static_cast<section_offset_type>(*it_o) >= end_offset)
+ continue;
+
+ // A -1 value in the symbol vector indicates a local section symbol.
+ if (gsym == reinterpret_cast<Symbol*>(-1))
+ {
+ is_section_symbol = true;
+ gsym = NULL;
+ }
+
+ if (first_iteration
+ && it_v->first != NULL)
+ {
+ Symbol_location loc;
+ loc.object = it_v->first;
+ loc.shndx = it_v->second;
+ loc.offset = convert_types<off_t, long long>(it_a->first
+ + it_a->second);
+ // Look through function descriptors
+ parameters->target().function_location(&loc);
+ if (loc.shndx != it_v->second)
+ {
+ it_v->second = loc.shndx;
+ // Modify symvalue/addend to the code entry.
+ it_a->first = loc.offset;
+ it_a->second = 0;
+ }
+ }
+
+ // ADDEND_STR stores the symbol value and addend and offset,
+ // each at most 16 hex digits long. it_a points to a pair
// where first is the symbol value and second is the
// addend.
- char addend_str[34];
- snprintf(addend_str, sizeof(addend_str), "%llx %llx",
- (*it_a).first, (*it_a).second);
+ char addend_str[50];
+
+ // It would be nice if we could use format macros in inttypes.h
+ // here but there are not in ISO/IEC C++ 1998.
+ snprintf(addend_str, sizeof(addend_str), "%llx %llx %llx",
+ static_cast<long long>((*it_a).first),
+ static_cast<long long>((*it_a).second),
+ static_cast<unsigned long long>(*it_o - start_offset));
+
+ // If the symbol pointed to by the reloc is not in an ordinary
+ // section or if the symbol type is not FROM_OBJECT, then the
+ // object is NULL.
+ if (it_v->first == NULL)
+ {
+ if (first_iteration)
+ {
+ // If the symbol name is available, use it.
+ if (gsym != NULL)
+ buffer.append(gsym->name());
+ // Append the addend.
+ buffer.append(addend_str);
+ buffer.append("@");
+ }
+ continue;
+ }
+
Section_id reloc_secn(it_v->first, it_v->second);
// If this reloc turns back and points to the same section,
// like a recursive call, use a special symbol to mark this.
- if (reloc_secn.first == secn.first
- && reloc_secn.second == secn.second)
+ if (reloc_secn.first == self_secn.first
+ && reloc_secn.second == self_secn.second)
{
if (first_iteration)
{
symtab->icf()->section_to_int_map();
Icf::Uniq_secn_id_map::iterator section_id_map_it =
section_id_map.find(reloc_secn);
- if (section_id_map_it != section_id_map.end())
+ bool is_sym_preemptible = (gsym != NULL
+ && !gsym->is_from_dynobj()
+ && !gsym->is_undefined()
+ && gsym->is_preemptible());
+ if (!is_sym_preemptible
+ && section_id_map_it != section_id_map.end())
{
// This is a reloc to a section that might be folded.
if (num_tracked_relocs)
uint64_t secn_flags = (it_v->first)->section_flags(it_v->second);
// This reloc points to a merge section. Hash the
// contents of this section.
- if ((secn_flags & elfcpp::SHF_MERGE) != 0)
+ if ((secn_flags & elfcpp::SHF_MERGE) != 0
+ && parameters->target().can_icf_inline_merge_sections())
{
uint64_t entsize =
(it_v->first)->section_entsize(it_v->second);
- long long offset = it_a->first + it_a->second;
+ long long offset = it_a->first;
+
+ // Handle SHT_RELA and SHT_REL addends. Only one of these
+ // addends exists. When pointing to a merge section, the
+ // addend only matters if it's relative to a section
+ // symbol. In order to unambiguously identify the target
+ // of the relocation, the compiler (and assembler) must use
+ // a local non-section symbol unless Symbol+Addend does in
+ // fact point directly to the target. (In other words,
+ // a bias for a pc-relative reference or a non-zero based
+ // access forces the use of a local symbol, and the addend
+ // is used only to provide that bias.)
+ uint64_t reloc_addend_value = 0;
+ if (is_section_symbol)
+ {
+ // Get the SHT_RELA addend. For RELA relocations,
+ // we have the addend from the relocation.
+ reloc_addend_value = it_a->second;
+
+ // Handle SHT_REL addends.
+ // For REL relocations, we need to fetch the addend
+ // from the section contents.
+ const unsigned char* reloc_addend_ptr =
+ contents + static_cast<unsigned long long>(*it_o);
+
+ // Update the addend value with the SHT_REL addend if
+ // available.
+ get_rel_addend(reloc_addend_ptr, *it_addend_size,
+ &reloc_addend_value);
+
+ // Ignore the addend when it is a negative value.
+ // See the comments in Merged_symbol_value::value
+ // in object.h.
+ if (reloc_addend_value < 0xffffff00)
+ offset = offset + reloc_addend_value;
+ }
+
section_size_type secn_len;
+
const unsigned char* str_contents =
(it_v->first)->section_contents(it_v->second,
&secn_len,
false) + offset;
+ gold_assert (offset < (long long) secn_len);
+
if ((secn_flags & elfcpp::SHF_STRINGS) != 0)
{
// String merge section.
}
else
{
- // Use the entsize to determine the length.
- buffer.append(reinterpret_cast<const
+ // Use the entsize to determine the length to copy.
+ uint64_t bufsize = entsize;
+ // If entsize is too big, copy all the remaining bytes.
+ if ((offset + entsize) > secn_len)
+ bufsize = secn_len - offset;
+ buffer.append(reinterpret_cast<const
char*>(str_contents),
- entsize);
+ bufsize);
}
+ buffer.append("@");
}
- else if ((*it_s) != NULL)
+ else if (gsym != NULL)
{
// If symbol name is available use that.
- const char *sym_name = (*it_s)->name();
- buffer.append(sym_name);
+ buffer.append(gsym->name());
// Append the addend.
buffer.append(addend_str);
buffer.append("@");
if (first_iteration)
{
buffer.append("Contents = ");
- buffer.append(reinterpret_cast<const char*>(contents), plen);
- // Store the section contents that dont change to avoid recomputing
+
+ const unsigned char* slice_end =
+ contents + std::min<section_offset_type>(plen, end_offset);
+
+ if (contents + start_offset < slice_end)
+ {
+ buffer.append(reinterpret_cast<const char*>(contents + start_offset),
+ slice_end - (contents + start_offset));
+ }
+ }
+
+ // Add any extra identity regions.
+ std::pair<Icf::Extra_identity_list::const_iterator,
+ Icf::Extra_identity_list::const_iterator>
+ extra_range = symtab->icf()->extra_identity_list().equal_range(secn);
+ for (Icf::Extra_identity_list::const_iterator it_ext = extra_range.first;
+ it_ext != extra_range.second; ++it_ext)
+ {
+ std::string external_fixed;
+ std::string external_all =
+ get_section_contents(first_iteration, &external_fixed,
+ it_ext->second.section, self_secn,
+ num_tracked_relocs, symtab,
+ kept_section_id, it_ext->second.offset,
+ it_ext->second.offset + it_ext->second.length);
+ buffer.append(external_fixed);
+ icf_reloc_buffer.append(external_all, external_fixed.length(),
+ std::string::npos);
+ }
+
+ if (first_iteration)
+ {
+ // Store the section contents that don't change to avoid recomputing
// during the next call to this function.
- (*section_contents)[section_num] = buffer;
+ *fixed_cache = buffer;
}
else
{
gold_assert(buffer.empty());
+
// Reuse the contents computed in the previous iteration.
- buffer.append((*section_contents)[section_num]);
+ buffer.append(*fixed_cache);
}
buffer.append(icf_reloc_buffer);
// KEPT_SECTION_ID : Vector which maps folded sections to kept sections.
// ID_SECTION : Vector mapping a section to an unique integer.
// IS_SECN_OR_GROUP_UNIQUE : To check if a section or a group of identical
-// sectionsis already known to be unique.
+// sections is already known to be unique.
// SECTION_CONTENTS : Store the section's text and relocs to non-ICF
// sections.
std::vector<unsigned int>* num_tracked_relocs,
std::vector<unsigned int>* kept_section_id,
const std::vector<Section_id>& id_section,
+ const std::vector<uint64_t>& section_addraligns,
std::vector<bool>* is_secn_or_group_unique,
std::vector<std::string>* section_contents)
{
continue;
Section_id secn = id_section[i];
+
+ // Lock the object so we can read from it. This is only called
+ // single-threaded from queue_middle_tasks, so it is OK to lock.
+ // Unfortunately we have no way to pass in a Task token.
+ const Task* dummy_task = reinterpret_cast<const Task*>(-1);
+ Task_lock_obj<Object> tl(dummy_task, secn.first);
+
std::string this_secn_contents;
uint32_t cksum;
+ std::string* this_secn_cache = &((*section_contents)[i]);
if (iteration_num == 1)
{
unsigned int num_relocs = 0;
- this_secn_contents = get_section_contents(true, secn, i, &num_relocs,
- symtab, (*kept_section_id),
- section_contents);
+ this_secn_contents = get_section_contents(true, this_secn_cache,
+ secn, secn, &num_relocs,
+ symtab, (*kept_section_id));
(*num_tracked_relocs)[i] = num_relocs;
}
else
{
if ((*kept_section_id)[i] != i)
{
- // This section is already folded into something. See
- // if it should point to a different kept section.
- unsigned int kept_section = (*kept_section_id)[i];
- if (kept_section != (*kept_section_id)[kept_section])
- {
- (*kept_section_id)[i] = (*kept_section_id)[kept_section];
- }
+ // This section is already folded into something.
continue;
}
- this_secn_contents = get_section_contents(false, secn, i, NULL,
- symtab, (*kept_section_id),
- section_contents);
+ this_secn_contents = get_section_contents(false, this_secn_cache,
+ secn, secn, NULL,
+ symtab, (*kept_section_id));
}
const unsigned char* this_secn_contents_array =
this_secn_contents.c_str(),
this_secn_contents.length()) != 0)
continue;
- (*kept_section_id)[i] = kept_section;
+
+ // Check section alignment here.
+ // The section with the larger alignment requirement
+ // should be kept. We assume alignment can only be
+ // zero or positive integral powers of two.
+ uint64_t align_i = section_addraligns[i];
+ uint64_t align_kept = section_addraligns[kept_section];
+ if (align_i <= align_kept)
+ {
+ (*kept_section_id)[i] = kept_section;
+ }
+ else
+ {
+ (*kept_section_id)[kept_section] = i;
+ it->second = i;
+ full_section_contents[kept_section].swap(
+ full_section_contents[i]);
+ }
+
converged = false;
break;
}
(*is_secn_or_group_unique)[i] = true;
}
+ // If a section was folded into another section that was later folded
+ // again then the former has to be updated.
+ for (unsigned int i = 0; i < id_section.size(); i++)
+ {
+ // Find the end of the folding chain
+ unsigned int kept = i;
+ while ((*kept_section_id)[kept] != kept)
+ {
+ kept = (*kept_section_id)[kept];
+ }
+ // Update every element of the chain
+ unsigned int current = i;
+ while ((*kept_section_id)[current] != kept)
+ {
+ unsigned int next = (*kept_section_id)[current];
+ (*kept_section_id)[current] = kept;
+ current = next;
+ }
+ }
+
return converged;
}
+// During safe icf (--icf=safe), only fold functions that are ctors or dtors.
+// This function returns true if the section name is that of a ctor or a dtor.
+
+static bool
+is_function_ctor_or_dtor(const std::string& section_name)
+{
+ const char* mangled_func_name = strrchr(section_name.c_str(), '.');
+ gold_assert(mangled_func_name != NULL);
+ if ((is_prefix_of("._ZN", mangled_func_name)
+ || is_prefix_of("._ZZ", mangled_func_name))
+ && (is_gnu_v3_mangled_ctor(mangled_func_name + 1)
+ || is_gnu_v3_mangled_dtor(mangled_func_name + 1)))
+ {
+ return true;
+ }
+ return false;
+}
+
+// Iterate through the .eh_frame section that has index
+// `ehframe_shndx` in `object`, adding entries to extra_identity_list_
+// that will cause the contents of each FDE and its CIE to be included
+// in the logical ICF identity of the function that the FDE refers to.
+
+bool
+Icf::add_ehframe_links(Relobj* object, unsigned int ehframe_shndx,
+ Reloc_info& relocs)
+{
+ section_size_type contents_len;
+ const unsigned char* pcontents = object->section_contents(ehframe_shndx,
+ &contents_len,
+ false);
+ const unsigned char* p = pcontents;
+ const unsigned char* pend = pcontents + contents_len;
+
+ Sections_reachable_info::iterator it_target = relocs.section_info.begin();
+ Sections_reachable_info::iterator it_target_end = relocs.section_info.end();
+ Offset_info::iterator it_offset = relocs.offset_info.begin();
+ Offset_info::iterator it_offset_end = relocs.offset_info.end();
+
+ // Maps section offset to the length of the CIE defined at that offset.
+ typedef Unordered_map<section_offset_type, section_size_type> Cie_map;
+ Cie_map cies;
+
+ uint32_t (*read_swap_32)(const unsigned char*);
+ if (object->is_big_endian())
+ read_swap_32 = &elfcpp::Swap<32, true>::readval;
+ else
+ read_swap_32 = &elfcpp::Swap<32, false>::readval;
+
+ // TODO: The logic for parsing the CIE/FDE framing is copied from
+ // Eh_frame::do_add_ehframe_input_section() and might want to be
+ // factored into a shared helper function.
+ while (p < pend)
+ {
+ if (pend - p < 4)
+ return false;
+
+ unsigned int len = read_swap_32(p);
+ p += 4;
+ if (len == 0)
+ {
+ // We should only find a zero-length entry at the end of the
+ // section.
+ if (p < pend)
+ return false;
+ break;
+ }
+ // We don't support a 64-bit .eh_frame.
+ if (len == 0xffffffff)
+ return false;
+ if (static_cast<unsigned int>(pend - p) < len)
+ return false;
+
+ const unsigned char* const pentend = p + len;
+
+ if (pend - p < 4)
+ return false;
+
+ unsigned int id = read_swap_32(p);
+ p += 4;
+
+ if (id == 0)
+ {
+ // CIE.
+ cies.insert(std::make_pair(p - pcontents, len - 4));
+ }
+ else
+ {
+ // FDE.
+ Cie_map::const_iterator it;
+ it = cies.find((p - pcontents) - (id - 4));
+ if (it == cies.end())
+ return false;
+
+ // Figure out which section this FDE refers into. The word at `p`
+ // is an address, and we expect to see a relocation there. If not,
+ // this FDE isn't ICF-relevant.
+ while (it_offset != it_offset_end
+ && it_target != it_target_end
+ && static_cast<ptrdiff_t>(*it_offset) < (p - pcontents))
+ {
+ ++it_offset;
+ ++it_target;
+ }
+ if (it_offset != it_offset_end
+ && it_target != it_target_end
+ && static_cast<ptrdiff_t>(*it_offset) == (p - pcontents))
+ {
+ // Found a reloc. Add this FDE and its CIE as extra identity
+ // info for the section it refers to.
+ Extra_identity_info rec_fde = {Section_id(object, ehframe_shndx),
+ p - pcontents, len - 4};
+ Extra_identity_info rec_cie = {Section_id(object, ehframe_shndx),
+ it->first, it->second};
+ extra_identity_list_.insert(std::make_pair(*it_target, rec_fde));
+ extra_identity_list_.insert(std::make_pair(*it_target, rec_cie));
+ }
+ }
+
+ p = pentend;
+ }
+
+ return true;
+}
// This is the main ICF function called in gold.cc. This does the
-// initialization and calls match_sections repeatedly (twice by default)
+// initialization and calls match_sections repeatedly (thrice by default)
// which computes the crc checksums and detects identical functions.
void
{
unsigned int section_num = 0;
std::vector<unsigned int> num_tracked_relocs;
+ std::vector<uint64_t> section_addraligns;
std::vector<bool> is_secn_or_group_unique;
std::vector<std::string> section_contents;
+ const Target& target = parameters->target();
// Decide which sections are possible candidates first.
p != input_objects->relobj_end();
++p)
{
- for (unsigned int i = 0;i < (*p)->shnum(); ++i)
+ // Lock the object so we can read from it. This is only called
+ // single-threaded from queue_middle_tasks, so it is OK to lock.
+ // Unfortunately we have no way to pass in a Task token.
+ const Task* dummy_task = reinterpret_cast<const Task*>(-1);
+ Task_lock_obj<Object> tl(dummy_task, *p);
+ std::vector<unsigned int> eh_frame_ind;
+
+ for (unsigned int i = 0; i < (*p)->shnum(); ++i)
{
- // Only looking to fold functions, so just look at .text sections.
- if (!is_prefix_of(".text.", (*p)->section_name(i).c_str()))
- continue;
+ const std::string section_name = (*p)->section_name(i);
+ if (!is_section_foldable_candidate(section_name))
+ {
+ if (is_prefix_of(".eh_frame", section_name.c_str()))
+ eh_frame_ind.push_back(i);
+ continue;
+ }
+
if (!(*p)->is_section_included(i))
continue;
if (parameters->options().gc_sections()
&& symtab->gc()->is_section_garbage(*p, i))
continue;
+ // With --icf=safe, check if the mangled function name is a ctor
+ // or a dtor. The mangled function name can be obtained from the
+ // section name by stripping the section prefix.
+ if (parameters->options().icf_safe_folding()
+ && !is_function_ctor_or_dtor(section_name)
+ && (!target.can_check_for_function_pointers()
+ || section_has_function_pointers(*p, i)))
+ {
+ continue;
+ }
this->id_section_.push_back(Section_id(*p, i));
this->section_id_[Section_id(*p, i)] = section_num;
this->kept_section_id_.push_back(section_num);
num_tracked_relocs.push_back(0);
+ section_addraligns.push_back((*p)->section_addralign(i));
is_secn_or_group_unique.push_back(false);
section_contents.push_back("");
section_num++;
}
+
+ for (std::vector<unsigned int>::iterator it_eh_ind = eh_frame_ind.begin();
+ it_eh_ind != eh_frame_ind.end(); ++it_eh_ind)
+ {
+ // gc_process_relocs() recorded relocations for this
+ // section even though we can't fold it. We need to
+ // use those relocations to associate other foldable
+ // sections with the FDEs and CIEs that are relevant
+ // to them, so we can avoid merging sections that
+ // don't have identical exception-handling behavior.
+
+ Section_id sect(*p, *it_eh_ind);
+ Reloc_info_list::iterator it_rel = this->reloc_info_list().find(sect);
+ if (it_rel != this->reloc_info_list().end())
+ {
+ if (!add_ehframe_links(*p, *it_eh_ind, it_rel->second))
+ {
+ gold_warning(_("could not parse eh_frame section %s(%s); ICF "
+ "might not preserve exception handling "
+ "behavior"),
+ (*p)->name().c_str(),
+ (*p)->section_name(*it_eh_ind).c_str());
+ }
+ }
+ }
}
unsigned int num_iterations = 0;
- // Default number of iterations to run ICF is 2.
+ // Default number of iterations to run ICF is 3.
unsigned int max_iterations = (parameters->options().icf_iterations() > 0)
? parameters->options().icf_iterations()
- : 2;
+ : 3;
bool converged = false;
num_iterations++;
converged = match_sections(num_iterations, symtab,
&num_tracked_relocs, &this->kept_section_id_,
- this->id_section_, &is_secn_or_group_unique,
- §ion_contents);
+ this->id_section_, section_addraligns,
+ &is_secn_or_group_unique, §ion_contents);
}
if (parameters->options().print_icf_sections())
program_name, num_iterations);
}
+ // Unfold --keep-unique symbols.
+ for (options::String_set::const_iterator p =
+ parameters->options().keep_unique_begin();
+ p != parameters->options().keep_unique_end();
+ ++p)
+ {
+ const char* name = p->c_str();
+ Symbol* sym = symtab->lookup(name);
+ if (sym == NULL)
+ {
+ gold_warning(_("Could not find symbol %s to unfold\n"), name);
+ }
+ else if (sym->source() == Symbol::FROM_OBJECT
+ && !sym->object()->is_dynamic())
+ {
+ Relobj* obj = static_cast<Relobj*>(sym->object());
+ bool is_ordinary;
+ unsigned int shndx = sym->shndx(&is_ordinary);
+ if (is_ordinary)
+ {
+ this->unfold_section(obj, shndx);
+ }
+ }
+
+ }
+
this->icf_ready();
}
+// Unfolds the section denoted by OBJ and SHNDX if folded.
+
+void
+Icf::unfold_section(Relobj* obj, unsigned int shndx)
+{
+ Section_id secn(obj, shndx);
+ Uniq_secn_id_map::iterator it = this->section_id_.find(secn);
+ if (it == this->section_id_.end())
+ return;
+ unsigned int section_num = it->second;
+ unsigned int kept_section_id = this->kept_section_id_[section_num];
+ if (kept_section_id != section_num)
+ this->kept_section_id_[section_num] = section_num;
+}
+
// This function determines if the section corresponding to the
// given object and index is folded based on if the kept section
// is different from this section.
bool
-Icf::is_section_folded(Object* obj, unsigned int shndx)
+Icf::is_section_folded(Relobj* obj, unsigned int shndx)
{
Section_id secn(obj, shndx);
Uniq_secn_id_map::iterator it = this->section_id_.find(secn);
// This function returns the folded section for the given section.
Section_id
-Icf::get_folded_section(Object* dup_obj, unsigned int dup_shndx)
+Icf::get_folded_section(Relobj* dup_obj, unsigned int dup_shndx)
{
Section_id dup_secn(dup_obj, dup_shndx);
Uniq_secn_id_map::iterator it = this->section_id_.find(dup_secn);
projects / deliverable / binutils-gdb.git / blobdiff