Convert mov foo@GOT(%reg), %reg to lea foo@GOTOFF(%reg), %reg

2015-04-01  Ilya Tocar  <ilya.tocar@intel.com>

	PR gold/17640
	* i386.cc (Target_i386::can_convert_mov_to_lea): New.
	(Target_i386::Scan::local): Don't create GOT entry, when we
	can convert GOT to GOTOFF.
	(Target_i386::Scan::global): Ditto.
	(Target_i386::Relocate::relocate): Convert  mov foo@GOT(%reg), %reg to
	lea foo@GOTOFF(%reg), %reg if possible.
	* testsuite/Makefile.am (i386_mov_to_lea): New test.
	* testsuite/i386_mov_to_lea1.s: New.
	* testsuite/i386_mov_to_lea2.s: Ditto.
	* testsuite/i386_mov_to_lea3.s: Ditto.
	* testsuite/i386_mov_to_lea4.s: Ditto.
	* testsuite/i386_mov_to_lea5.s: Ditto.
	* testsuite/i386_mov_to_lea.sh: Ditto.

1 files changed, 94 insertions, 33 deletions

diff --git a/gold/i386.cc b/gold/i386.cc
index 3bc3d94..086314e 100644
--- a/gold/i386.cc
+++ b/gold/i386.cc
@@ -738,6 +738,26 @@ class Target_i386 : public Sized_target<32, false>
   static tls::Tls_optimization
   optimize_tls_reloc(bool is_final, int r_type);
 
+  // Check if relocation against this symbol is a candidate for
+  // conversion from
+  // mov foo@GOT(%reg), %reg
+  // to
+  // lea foo@GOTOFF(%reg), %reg.
+  static bool
+  can_convert_mov_to_lea(const Symbol* gsym)
+  {
+    gold_assert(gsym != NULL);
+    return (gsym->type() != elfcpp::STT_GNU_IFUNC
+	    && !gsym->is_undefined ()
+	    && !gsym->is_from_dynobj()
+	    && !gsym->is_preemptible()
+	    && (!parameters->options().shared()
+		|| (gsym->visibility() != elfcpp::STV_DEFAULT
+		    && gsym->visibility() != elfcpp::STV_PROTECTED)
+		|| parameters->options().Bsymbolic())
+	    && strcmp(gsym->name(), "_DYNAMIC") != 0);
+  }
+
   // Get the GOT section, creating it if necessary.
   Output_data_got<32, false>*
   got_section(Symbol_table*, Layout*);
@@ -1835,8 +1855,26 @@ Target_i386::Scan::local(Symbol_table* symtab,
 
     case elfcpp::R_386_GOT32:
       {
-	// The symbol requires a GOT entry.
+	// We need GOT section.
 	Output_data_got<32, false>* got = target->got_section(symtab, layout);
+
+	// If the relocation symbol isn't IFUNC,
+	// and is local, then we will convert
+	// mov foo@GOT(%reg), %reg
+	// to
+	// lea foo@GOTOFF(%reg), %reg
+	// in Relocate::relocate.
+	if (reloc.get_r_offset() >= 2
+	    && lsym.get_st_type() != elfcpp::STT_GNU_IFUNC)
+	  {
+	    section_size_type stype;
+	    const unsigned char* view = object->section_contents(data_shndx,
+								 &stype, true);
+	    if (view[reloc.get_r_offset() - 2] == 0x8b)
+	      break;
+	  }
+
+	// Otherwise, the symbol requires a GOT entry.
 	unsigned int r_sym = elfcpp::elf_r_sym<32>(reloc.get_r_info());
 
 	// For a STT_GNU_IFUNC symbol we want the PLT offset.  That
@@ -2229,8 +2267,24 @@ Target_i386::Scan::global(Symbol_table* symtab,
 
     case elfcpp::R_386_GOT32:
       {
-	// The symbol requires a GOT entry.
+	// The symbol requires a GOT section.
 	Output_data_got<32, false>* got = target->got_section(symtab, layout);
+
+	// If we convert this from
+	// mov foo@GOT(%reg), %reg
+	// to
+	// lea foo@GOTOFF(%reg), %reg
+	// in Relocate::relocate, then there is nothing to do here.
+	if (reloc.get_r_offset() >= 2
+	    && Target_i386::can_convert_mov_to_lea(gsym))
+	  {
+	    section_size_type stype;
+	    const unsigned char* view = object->section_contents(data_shndx,
+								 &stype, true);
+	    if (view[reloc.get_r_offset() - 2] == 0x8b)
+	      break;
+	  }
+
 	if (gsym->final_value_is_known())
 	  {
 	    // For a STT_GNU_IFUNC symbol we want the PLT address.
@@ -2732,35 +2786,6 @@ Target_i386::Relocate::relocate(const Relocate_info<32, false>* relinfo,
 	}
     }
 
-  // Get the GOT offset if needed.
-  // The GOT pointer points to the end of the GOT section.
-  // We need to subtract the size of the GOT section to get
-  // the actual offset to use in the relocation.
-  bool have_got_offset = false;
-  unsigned int got_offset = 0;
-  switch (r_type)
-    {
-    case elfcpp::R_386_GOT32:
-      if (gsym != NULL)
-	{
-	  gold_assert(gsym->has_got_offset(GOT_TYPE_STANDARD));
-	  got_offset = (gsym->got_offset(GOT_TYPE_STANDARD)
-			- target->got_size());
-	}
-      else
-	{
-	  unsigned int r_sym = elfcpp::elf_r_sym<32>(rel.get_r_info());
-	  gold_assert(object->local_has_got_offset(r_sym, GOT_TYPE_STANDARD));
-	  got_offset = (object->local_got_offset(r_sym, GOT_TYPE_STANDARD)
-			- target->got_size());
-	}
-      have_got_offset = true;
-      break;
-
-    default:
-      break;
-    }
-
   switch (r_type)
     {
     case elfcpp::R_386_NONE:
@@ -2809,8 +2834,44 @@ Target_i386::Relocate::relocate(const Relocate_info<32, false>* relinfo,
       break;
 
     case elfcpp::R_386_GOT32:
-      gold_assert(have_got_offset);
-      Relocate_functions<32, false>::rel32(view, got_offset);
+      // Convert
+      // mov foo@GOT(%reg), %reg
+      // to
+      // lea foo@GOTOFF(%reg), %reg
+      // if possible.
+      if (rel.get_r_offset() >= 2
+	  && view[-2] == 0x8b
+	  && ((gsym == NULL && !psymval->is_ifunc_symbol())
+	      || (gsym != NULL
+		  && Target_i386::can_convert_mov_to_lea(gsym))))
+	{
+	  view[-2] = 0x8d;
+	  elfcpp::Elf_types<32>::Elf_Addr value;
+	  value = (psymval->value(object, 0)
+	           - target->got_plt_section()->address());
+	  Relocate_functions<32, false>::rel32(view, value);
+	}
+      else
+	{
+	  // The GOT pointer points to the end of the GOT section.
+	  // We need to subtract the size of the GOT section to get
+	  // the actual offset to use in the relocation.
+	  unsigned int got_offset = 0;
+	  if (gsym != NULL)
+	    {
+	      gold_assert(gsym->has_got_offset(GOT_TYPE_STANDARD));
+	      got_offset = (gsym->got_offset(GOT_TYPE_STANDARD)
+			    - target->got_size());
+	    }
+	  else
+	    {
+	      unsigned int r_sym = elfcpp::elf_r_sym<32>(rel.get_r_info());
+	      gold_assert(object->local_has_got_offset(r_sym, GOT_TYPE_STANDARD));
+	      got_offset = (object->local_got_offset(r_sym, GOT_TYPE_STANDARD)
+			    - target->got_size());
+	    }
+	  Relocate_functions<32, false>::rel32(view, got_offset);
+	}
       break;
 
     case elfcpp::R_386_GOTOFF: