Patch for ICF string inline bug for SHT_REL sections.

[Sriraman Tallam <tmsriram at google dot com>]

Hi,

    I found a bug in ICF where it incorrectly inlines strings pointed
to by SHT_REL relocation types. These relocation types encode the
addend info at the relocation offset in the text section and ICF
simply ignores them. Here is a simple example showing the bug.

test_1.cc
----------


#include <string>
std::string name1() { return "Name1"; }
std::string bar()
{
  return "AAAAAA";
}

int main()
{
  return 0;
}

test_2.cc
----------


#include <string>
std::string name2() { return "Name2"; }
std::string foo()
{
  return "AAAAAA";
}

$ gcc -ffunction-sections -fdata-sections -Wl,--print-icf-sections,--icf=all -O2
ld: ICF folding section '.text._Z5name2v' in file 'test_2.o'into
'.text._Z5name1v' in file 'test_1.o

Function name1() is folded into name2() which is wrong. This happens
because the addend is ignored and the wrong string "AAAAAA" is
inlined. The attached patch fixes it.

2010-07-18  Sriraman Tallam  <tmsriram@google.com>

	* gc.h (gc_process_relocs): Save the section header type for use by
	ICF.
	* icf.cc (get_section_contents): Get the addend from the text section
	for SHT_REL relocation sections.
	* icf.h (Icf::Sh_type_info): New typedef.
	(Icf::Reloc_info): Add new member sh_type_info.

Is this ok to submit ?

Thanks,
-Sri.

Attachment: icf_addend_sht_rel_bug.txt
Description: Text document