* layout.cc (Layout::special_ordering_of_input_section): New
function. (Layout::layout): If input section requires special ordering, must sort input sections. (Layout::make_output_section): May sort .text input sections. (Layout::is_section_name_prefix_grouped): Remove. * layout.h (class Layout): Declare special_ordering_of_input_section. Don't declare is_section_name_prefix_grouped. * output.cc (Output_section::add_input_section): Revert last change. (Output_section::Input_section_sort::match_file_name): Don't crash if called on output section data. (Output_section::Input_section_sort_compare): Sort based on special ordering. (Output_section::Input_section_sort_section_order_index_compare): Revert last patch. (Output_section::sort_attached_input_sections): Likewise.
This commit is contained in:
Ian Lance Taylor
parent
600e715a7b
commit
edcac0c105
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@ -1,14 +1,35 @@
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2012-12-20 Ian Lance Taylor <iant@google.com>
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* layout.cc (Layout::special_ordering_of_input_section): New
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function.
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(Layout::layout): If input section requires special ordering, must
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sort input sections.
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(Layout::make_output_section): May sort .text input sections.
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(Layout::is_section_name_prefix_grouped): Remove.
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* layout.h (class Layout): Declare
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special_ordering_of_input_section. Don't declare
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is_section_name_prefix_grouped.
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* output.cc (Output_section::add_input_section): Revert last
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change.
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(Output_section::Input_section_sort::match_file_name): Don't crash
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if called on output section data.
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(Output_section::Input_section_sort_compare): Sort based on
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special ordering.
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(Output_section::Input_section_sort_section_order_index_compare):
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Revert last patch.
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(Output_section::sort_attached_input_sections): Likewise.
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2012-12-18 Sriraman Tallam <tmsriram@google.com>
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* layout.cc (Layout::is_section_name_prefix_grouped): New function.
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* layout.cc (Layout::is_section_name_prefix_grouped): New function.
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* layout.h (Layout::is_section_name_prefix_grouped): New function.
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* output.cc (Output_section::add_input_section): Check if section
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name contains special prefix. Keep input sections to sort such
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sections.
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(Output_section::Input_section_sort_section_order_index_compare
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::operator()): Group sections according to prefixes.
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* (Output_section::sort_attached_input_sections): Add condition
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to Input_section_entry constructor call.
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(Output_section::sort_attached_input_sections): Add condition to
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Input_section_entry constructor call.
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* testsuite/Makefile.am (text_section_grouping): New test.
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* testsuite/Makefile.in: Regenerate.
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* testsuite/text_section_grouping.cc: New file.
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@ -1033,6 +1033,33 @@ Layout::init_fixed_output_section(const char* name,
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return os;
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}
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// Return the index by which an input section should be ordered. This
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// is used to sort some .text sections, for compatibility with GNU ld.
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int
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Layout::special_ordering_of_input_section(const char* name)
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{
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// The GNU linker has some special handling for some sections that
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// wind up in the .text section. Sections that start with these
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// prefixes must appear first, and must appear in the order listed
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// here.
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static const char* const text_section_sort[] =
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{
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".text.unlikely",
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".text.exit",
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".text.startup",
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".text.hot"
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};
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for (size_t i = 0;
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i < sizeof(text_section_sort) / sizeof(text_section_sort[0]);
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i++)
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if (is_prefix_of(text_section_sort[i], name))
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return i;
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return -1;
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}
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// Return the output section to use for input section SHNDX, with name
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// NAME, with header HEADER, from object OBJECT. RELOC_SHNDX is the
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// index of a relocation section which applies to this section, or 0
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@ -1120,6 +1147,13 @@ Layout::layout(Sized_relobj_file<size, big_endian>* object, unsigned int shndx,
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|| strcmp(name, ".dtors") == 0))))
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os->set_must_sort_attached_input_sections();
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// By default the GNU linker sorts some special text sections ahead
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// of others. We are compatible.
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if (!this->script_options_->saw_sections_clause()
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&& !parameters->options().relocatable()
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&& Layout::special_ordering_of_input_section(name) >= 0)
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os->set_must_sort_attached_input_sections();
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// If this is a .ctors or .ctors.* section being mapped to a
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// .init_array section, or a .dtors or .dtors.* section being mapped
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// to a .fini_array section, we will need to reverse the words if
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@ -1607,6 +1641,15 @@ Layout::make_output_section(const char* name, elfcpp::Elf_Word type,
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|| strcmp(name, ".dtors") == 0))))
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os->set_may_sort_attached_input_sections();
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// The GNU linker by default sorts .text.{unlikely,exit,startup,hot}
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// sections before other .text sections. We are compatible. We
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// need to know that this might happen before we attach any input
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// sections.
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if (!this->script_options_->saw_sections_clause()
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&& !parameters->options().relocatable()
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&& strcmp(name, ".text") == 0)
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os->set_may_sort_attached_input_sections();
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// Check for .stab*str sections, as .stab* sections need to link to
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// them.
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if (type == elfcpp::SHT_STRTAB
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@ -2409,20 +2452,6 @@ Layout::relaxation_loop_body(
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return off;
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}
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// By default, gold groups input sections with certain prefixes. This
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// function returns true if this section name NAME contains such a prefix.
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bool
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Layout::is_section_name_prefix_grouped(const char *name)
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{
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if (is_prefix_of(".text.unlikely", name)
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|| is_prefix_of(".text.startup", name)
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|| is_prefix_of(".text.hot", name))
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return true;
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return false;
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}
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// Search the list of patterns and find the postion of the given section
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// name in the output section. If the section name matches a glob
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// pattern and a non-glob name, then the non-glob position takes
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@ -553,11 +553,14 @@ class Layout
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void
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insert_section_segment_map(Const_section_id secn, Unique_segment_info *s);
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// By default, gold groups input sections with certain prefixes. This
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// function returns true if this section name NAME contains such a prefix.
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bool
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is_section_name_prefix_grouped(const char *name);
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// Some input sections require special ordering, for compatibility
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// with GNU ld. Given the name of an input section, return -1 if it
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// does not require special ordering. Otherwise, return the index
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// by which it should be ordered compared to other input sections
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// that require special ordering.
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static int
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special_ordering_of_input_section(const char* name);
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bool
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is_section_ordering_specified()
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{ return this->section_ordering_specified_; }
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@ -2478,19 +2478,6 @@ Output_section::add_input_section(Layout* layout,
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}
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}
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// The GNU linker groups input sections whose names match .text.unlikely.*.
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// This is used to get better code layout. We are compatible.
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// Additionally, it could also be beneficial to group .text.hot.*,
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// .text.startup.* prefixed input sections. Function
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// "is_section_name_prefix_grouped" in layout.cc determines the input
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// section prefixes that must be grouped.
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if (!have_sections_script
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&& !parameters->options().relocatable()
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&& !this->input_section_order_specified()
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&& !this->must_sort_attached_input_sections()
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&& layout->is_section_name_prefix_grouped(secname))
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this->set_input_section_order_specified();
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// We need to keep track of this section if we are already keeping
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// track of sections, or if we are relaxing. Also, if this is a
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// section which requires sorting, or which may require sorting in
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@ -2504,8 +2491,7 @@ Output_section::add_input_section(Layout* layout,
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|| this->must_sort_attached_input_sections()
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|| parameters->options().user_set_Map()
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|| parameters->target().may_relax()
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|| layout->is_section_ordering_specified()
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|| this->input_section_order_specified())
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|| layout->is_section_ordering_specified())
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{
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Input_section isecn(object, shndx, input_section_size, addralign);
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/* If section ordering is requested by specifying a ordering file,
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@ -3337,7 +3323,11 @@ class Output_section::Input_section_sort_entry
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// in order to better support gcc, and we need to be compatible.
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bool
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match_file_name(const char* file_name) const
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{ return Layout::match_file_name(this->input_section_.relobj(), file_name); }
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{
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if (this->input_section_.is_output_section_data())
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return false;
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return Layout::match_file_name(this->input_section_.relobj(), file_name);
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}
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// Returns 1 if THIS should appear before S in section order, -1 if S
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// appears before THIS and 0 if they are not comparable.
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@ -3409,6 +3399,19 @@ Output_section::Input_section_sort_compare::operator()(
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return s1.index() < s2.index();
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}
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// Some input section names have special ordering requirements.
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int o1 = Layout::special_ordering_of_input_section(s1.section_name().c_str());
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int o2 = Layout::special_ordering_of_input_section(s2.section_name().c_str());
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if (o1 != o2)
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{
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if (o1 < 0)
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return false;
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else if (o2 < 0)
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return true;
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else
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return o1 < o2;
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}
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// A section with a priority follows a section without a priority.
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bool s1_has_priority = s1.has_priority();
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bool s2_has_priority = s2.has_priority();
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@ -3498,9 +3501,7 @@ Output_section::Input_section_sort_init_fini_compare::operator()(
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// Return true if S1 should come before S2. Sections that do not match
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// any pattern in the section ordering file are placed ahead of the sections
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// that match some pattern. This function is also used to group text according
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// to their prefix. The following prefixes are recognized: ".text.startup",
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// ".text.hot", and ".text.unlikely".
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// that match some pattern.
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bool
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Output_section::Input_section_sort_section_order_index_compare::operator()(
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@ -3510,59 +3511,11 @@ Output_section::Input_section_sort_section_order_index_compare::operator()(
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unsigned int s1_secn_index = s1.input_section().section_order_index();
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unsigned int s2_secn_index = s2.input_section().section_order_index();
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// If section ordering is specified, it takes precedence.
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if (s1_secn_index != s2_secn_index)
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return s1_secn_index < s2_secn_index;
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// Sort all the sections with no names to the end.
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if (!s1.section_has_name() || !s2.section_has_name())
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{
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if (s1.section_has_name())
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return true;
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if (s2.section_has_name())
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return false;
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return s1.index() < s2.index();
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}
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// If it is a text section use the following order:
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// .text.unlikely, .text.startup, .text.hot. The prefixes
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// must match those in function is_section_name_prefix_grouped
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// in layout.cc
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const char* section_prefix [] =
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{
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".text.unlikely",
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".text.startup",
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".text.hot"
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};
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const unsigned int num_prefixes
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= sizeof(section_prefix) / sizeof(const char*);
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unsigned int s1_group_index = num_prefixes;
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unsigned int s2_group_index = num_prefixes;
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unsigned int flag_done = 0;
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for (unsigned int i = 0; i < num_prefixes && flag_done < 2; i++)
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{
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if (s1_group_index == num_prefixes
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&& is_prefix_of(section_prefix[i], s1.section_name().c_str()))
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{
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s1_group_index = i;
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flag_done++;
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}
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if (s2_group_index == num_prefixes
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&& is_prefix_of(section_prefix[i], s2.section_name().c_str()))
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{
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s2_group_index = i;
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flag_done++;
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}
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}
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if (s1_group_index == s2_group_index)
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// Keep input order if section ordering cannot determine order.
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if (s1_secn_index == s2_secn_index)
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return s1.index() < s2.index();
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else
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return s1_group_index < s2_group_index;
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return s1_secn_index < s2_secn_index;
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}
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// This updates the section order index of input sections according to the
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@ -3623,8 +3576,7 @@ Output_section::sort_attached_input_sections()
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p != this->input_sections_.end();
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++p, ++i)
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sort_list.push_back(Input_section_sort_entry(*p, i,
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(this->must_sort_attached_input_sections()
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|| this->input_section_order_specified())));
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this->must_sort_attached_input_sections()));
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// Sort the input sections.
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if (this->must_sort_attached_input_sections())
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