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* gc.h (gc_process_relocs): Call is_section_foldable_candidate to

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check for .text or .gnu.linkonce.t sections.
	* icf.cc (Icf::find_identical_sections): Ditto.
	Change the detection for mangled function name within the section
	name.
	* icf.h (is_section_foldable_candidate): New function.
This commit is contained in:
Sriraman Tallam 2010-01-04 19:08:39 +00:00
parent b3f4152256
commit 55a2bb3546
4 changed files with 35 additions and 12 deletions
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9
gold/ChangeLog
View file

@ -1,3 +1,12 @@
2010-01-04 Sriraman Tallam <tmsriram@google.com>
* gc.h (gc_process_relocs): Call is_section_foldable_candidate to
check for .text or .gnu.linkonce.t sections.
* icf.cc (Icf::find_identical_sections): Ditto.
Change the detection for mangled function name within the section
name.
* icf.h (is_section_foldable_candidate): New function.
2009-12-30 Ian Lance Taylor <iant@google.com>
PR 10980

4
gold/gc.h
View file

@ -1,6 +1,6 @@
// gc.h -- garbage collection of unused sections
// Copyright 2009 Free Software Foundation, Inc.
// Copyright 2009, 2010 Free Software Foundation, Inc.
// Written by Sriraman Tallam <tmsriram@google.com>.
// This file is part of gold.
@ -163,7 +163,7 @@ gc_process_relocs(
bool is_icf_tracked = false;
if (parameters->options().icf_enabled()
&& is_prefix_of(".text.", (src_obj)->section_name(src_indx).c_str()))
&& is_section_foldable_candidate(src_obj->section_name(src_indx).c_str()))
{
is_icf_tracked = true;
Section_id src_id(src_obj, src_indx);

21
gold/icf.cc
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@ -1,6 +1,6 @@
// icf.cc -- Identical Code Folding.
//
// Copyright 2009 Free Software Foundation, Inc.
// Copyright 2009, 2010 Free Software Foundation, Inc.
// Written by Sriraman Tallam <tmsriram@google.com>.
// This file is part of gold.
@ -23,7 +23,7 @@
// 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
@ -34,8 +34,8 @@
// 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 :
@ -102,7 +102,7 @@
// behaviour.
//
//
// 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
@ -570,17 +570,20 @@ Icf::find_identical_sections(const Input_objects* input_objects,
for (unsigned int i = 0;i < (*p)->shnum(); ++i)
{
const char* section_name = (*p)->section_name(i).c_str();
// Only looking to fold functions, so just look at .text sections.
if (!is_prefix_of(".text.", section_name))
if (!is_section_foldable_candidate(section_name))
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 mangled name is a ctor or a dtor.
// 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.
const char* mangled_func_name = strrchr(section_name, '.');
gold_assert(mangled_func_name != NULL);
if (parameters->options().icf_safe_folding()
&& !is_function_ctor_or_dtor(section_name + 6))
&& !is_function_ctor_or_dtor(mangled_func_name + 1))
continue;
this->id_section_.push_back(Section_id(*p, i));
this->section_id_[Section_id(*p, i)] = section_num;

13
gold/icf.h
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@ -1,6 +1,6 @@
// icf.h -- Identical Code Folding
// Copyright 2009 Free Software Foundation, Inc.
// Copyright 2009, 2010 Free Software Foundation, Inc.
// Written by Sriraman Tallam <tmsriram@google.com>.
// This file is part of gold.
@ -139,6 +139,17 @@ class Icf
Addend_list addend_reloc_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.
inline bool
is_section_foldable_candidate(const char* section_name)
{
return (is_prefix_of(".text", section_name)
|| is_prefix_of(".gnu.linkonce.t", section_name));
}
} // End of namespace gold.
#endif