2013-04-29 Alexander Ivchenko <alexander.ivchenko@intel.com>

gold/
	* output.cc (Output_section::add_merge_input_section): Allow
	to merge sections if the alignment is more than character size.
	* merge.h (Output_merge_string::Output_merge_string): Remove
	assert.
	* merge.cc (Output_merge_string<Char_type>::do_add_input_section): Count
	only not-null strings. Check the alignment of strings.
	* stringpool.h
	(Stringpool_template<Stringpool_char>::Stringpool_template): Add
	alignment as the argument.
	(Stringpool_template<Stringpool_char>::addralign_): New class member.
	* stringpool.cc (Stringpool_template<Stringpool_char>::new_key_offset):
	Align non-zero length strings according to the addralign_.
	(Stringpool_template<Stringpool_char>::set_string_offsets):
	Updating offsets according to the given alignment.
	* testsuite/Makefile.am (text_section_grouping): Test if string
	literals are getting merged.
	* testsuite/Makefile.in: Regenerate.
	* testsuite/merge_string_literals_1.c: New file.
	* testsuite/merge_string_literals_2.c: Ditto.
	* testsuite/merge_string_literals.sh: Ditto.

1 files changed, 30 insertions, 6 deletions

diff --git a/gold/merge.cc b/gold/merge.cc
index dde43e9..6480bd9 100644
--- a/gold/merge.cc
+++ b/gold/merge.cc
@@ -540,25 +540,43 @@ Output_merge_string<Char_type>::do_add_input_section(Relobj* object,
   this->merged_strings_lists_.push_back(merged_strings_list);
   Merged_strings& merged_strings = merged_strings_list->merged_strings;
 
-  // Count the number of strings in the section and size the list.
+  // Count the number of non-null strings in the section and size the list.
   size_t count = 0;
-  for (const Char_type* pt = p; pt < pend0; pt += string_length(pt) + 1)
-    ++count;
+  for (const Char_type* pt = p, len = string_length(pt);
+       pt < pend0;
+       pt += len + 1)
+    if (len != 0)
+      ++count;
   if (pend0 < pend)
     ++count;
   merged_strings.reserve(count + 1);
 
   // The index I is in bytes, not characters.
   section_size_type i = 0;
+
+  // We assume here that the beginning of the section is correctly
+  // aligned, so each string within the section must retain the same
+  // modulo.
+  uintptr_t init_align_modulo = (reinterpret_cast<uintptr_t>(pdata)
+				 & (this->addralign() - 1));
+  bool has_misaligned_strings = false;
+
   while (p < pend0)
     {
       size_t len = string_length(p);
 
-      Stringpool::Key key;
-      this->stringpool_.add_with_length(p, len, true, &key);
+      if (len != 0)
+	{
+	  // Within merge input section each string must be aligned.
+	  if ((reinterpret_cast<uintptr_t>(p) & (this->addralign() - 1))
+	      != init_align_modulo)
+	    has_misaligned_strings = true;
 
-      merged_strings.push_back(Merged_string(i, key));
+	  Stringpool::Key key;
+	  this->stringpool_.add_with_length(p, len, true, &key);
 
+	  merged_strings.push_back(Merged_string(i, key));
+	}
       p += len + 1;
       i += (len + 1) * sizeof(Char_type);
     }
@@ -581,6 +599,12 @@ Output_merge_string<Char_type>::do_add_input_section(Relobj* object,
   this->input_count_ += count;
   this->input_size_ += len;
 
+  if (has_misaligned_strings)
+    gold_warning(_("%s: section %s contains incorrectly aligned strings;"
+		   " the alignment of those strings won't be preserved"),
+		 object->name().c_str(),
+		 object->section_name(shndx).c_str());
+
   // For script processing, we keep the input sections.
   if (this->keeps_input_sections())
     record_input_section(object, shndx);