Fix problem with ICF where diffs in EH frame info is ignored.

	PR gold/21066
	* gc.h (gc_process_relocs): Track relocations in .eh_frame sections
	when ICF is enabled, even though the .eh_frame sections themselves
	are not foldable.
	* icf.cc (get_section_contents): Change arguments to permit operation
	on just part of a section. Include extra identity regions in the
	referring section's contents recursively.
	(match_sections): Lock object here instead of in get_section_contents
	so that get_section_contents can operate recursively.
	(Icf::add_ehframe_links): New method.
	(Icf::find_identical_sections): Pass .eh_frame sections to
	add_ehframe_links(). Increase default iteration count from 2 to 3
	because handling exception info typically requires one extra iteration.
	* icf.h (Icf::extra_identity_list_): New data member with accessor.
	(is_section_foldable_candidate): Include .gcc_except_table sections.
	* options.h: Update documentation for new default ICF iteration count.
	* testsuite/Makefile.am (icf_test_pr21066): New test case.
	* testsuite/Makefile.in: Regenerate.
	* testsuite/icf_test_pr21066.cc: New source file.
	* testsuite/icf_test_pr21066.sh: New test script.

1 files changed, 30 insertions, 0 deletions

diff --git a/gold/icf.h b/gold/icf.h
index e99ac06..7f8e841 100644
--- a/gold/icf.h
+++ b/gold/icf.h
@@ -64,6 +64,19 @@ class Icf
   typedef Unordered_map<Section_id, Reloc_info,
                         Section_id_hash> Reloc_info_list;
 
+  // A region of some other section that should be considered part of
+  // a section for ICF purposes. This is used to avoid folding sections
+  // that have identical text and relocations but different .eh_frame
+  // information.
+  typedef struct
+  {
+	Section_id section;
+	section_offset_type offset;
+	section_size_type length;
+  } Extra_identity_info;
+
+  typedef std::multimap<Section_id, Extra_identity_info> Extra_identity_list;
+
   Icf()
   : id_section_(), section_id_(), kept_section_id_(),
     fptr_section_id_(),
@@ -137,6 +150,12 @@ class Icf
   reloc_info_list()
   { return this->reloc_info_list_; }
 
+  // Returns a map from section to region of a different section that should
+  // be considered part of the key section for ICF purposes.
+  Extra_identity_list&
+  extra_identity_list()
+  { return this->extra_identity_list_; }
+
   // Returns a mapping of each section to a unique integer.
   Uniq_secn_id_map&
   section_to_int_map()
@@ -144,6 +163,10 @@ class Icf
 
  private:
 
+  bool
+  add_ehframe_links(Relobj* object, unsigned int ehframe_shndx,
+		    Reloc_info& ehframe_relocs);
+
   // Maps integers to sections.
   std::vector<Section_id> id_section_;
   // Does the reverse.
@@ -160,17 +183,24 @@ class Icf
   bool icf_ready_;
   // This list is populated by gc_process_relocs in gc.h.
   Reloc_info_list reloc_info_list_;
+  // Regions of other sections that should be considered part of
+  // each section for ICF purposes.
+  Extra_identity_list extra_identity_list_;
 };
 
 // This function returns true if this section corresponds to a function that
 // should be considered by icf as a possible candidate for folding.  Some
 // earlier gcc versions, like 4.0.3, put constructors and destructors in
 // .gnu.linkonce.t sections and hence should be included too.
+// The mechanism used to safely fold functions referenced by .eh_frame
+// requires folding .gcc_except_table sections as well; see "Notes regarding
+// C++ exception handling" at the top of icf.cc for an explanation why.
 inline bool
 is_section_foldable_candidate(const std::string& section_name)
 {
   const char* section_name_cstr = section_name.c_str();
   return (is_prefix_of(".text", section_name_cstr)
+          || is_prefix_of(".gcc_except_table", section_name_cstr)
           || is_prefix_of(".gnu.linkonce.t", section_name_cstr));
 }