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authorSriraman Tallam <tmsriram@google.com>2014-05-13 10:51:48 -0700
committerSriraman Tallam <tmsriram@google.com>2014-05-13 10:55:11 -0700
commita82bef932ec11cc16f205427f8a056c3c0ea517d (patch)
tree352f54fa01c8dc420676ee779b863fb457ba929d /gold/i386.cc
parent033c337911594898b44678fa10b47ee19dd234b5 (diff)
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With -pie and x86, the linker complains if it sees a PC-relative relocation
to access a global as it expects a GOTPCREL relocation. This is really not necessary as the linker could use a copy relocation to get around it. This patch enables copy relocations with pie. Context: This is useful because currently the GCC compiler with option -fpie makes every extern global access go through the GOT. That is because the compiler cannot tell if a global will end up being defined in the executable or not and is conservative. This ends up hurting performance when the binary is linked as mostly static where most of the globals do end up being defined in the executable. By allowing copy relocs with fPIE, the compiler need not generate a GOTPCREL(GOT access) for any global access. It can safely assume that all globals will be defined in the executable and generate a PC-relative access instead. Gold can then create a copy reloc for only the undefined globals. gold/ * symtab.h (may_need_copy_reloc): Remove check for position independent code. * x86_64.cc (Target_x86_64<size>::Scan::global): Add check for no position independence before pc absolute may_need_copy_reloc call. Add check for executable output befor pc relative may_need_copy_reloc call. * i386.cc: Ditto. * arm.cc: Ditto. * sparc.cc: Ditto. * tilegx.cc: Ditto. * powerpc.cc: Add check for no position independence before may_need_copy_reloc calls. * testsuite/pie_copyrelocs_test.cc: New file. * testsuite/pie_copyrelocs_shared_test.cc: New file. * Makefile.am (pie_copyrelocs_test): New test. * Makefile.in: Regenerate.
Diffstat (limited to 'gold/i386.cc')
-rw-r--r--gold/i386.cc6
1 files changed, 4 insertions, 2 deletions
diff --git a/gold/i386.cc b/gold/i386.cc
index ed7f3f9..d28c444 100644
--- a/gold/i386.cc
+++ b/gold/i386.cc
@@ -2149,7 +2149,8 @@ Target_i386::Scan::global(Symbol_table* symtab,
// Make a dynamic relocation if necessary.
if (gsym->needs_dynamic_reloc(Scan::get_reference_flags(r_type)))
{
- if (gsym->may_need_copy_reloc())
+ if (!parameters->options().output_is_position_independent()
+ && gsym->may_need_copy_reloc())
{
target->copy_reloc(symtab, layout, object,
data_shndx, output_section, gsym, reloc);
@@ -2210,7 +2211,8 @@ Target_i386::Scan::global(Symbol_table* symtab,
// Make a dynamic relocation if necessary.
if (gsym->needs_dynamic_reloc(Scan::get_reference_flags(r_type)))
{
- if (gsym->may_need_copy_reloc())
+ if (parameters->options().output_is_executable()
+ && gsym->may_need_copy_reloc())
{
target->copy_reloc(symtab, layout, object,
data_shndx, output_section, gsym, reloc);