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[GOLD] PowerPC got reloc optimisation 

Note that gold won't remove unused GOT entries, in contrast to ld.bfd
which will.

	* powerpc.cc (Powerpc_relobj::make_got_relative): New function.
	(relative_value_is_known): New functions.
	(Target_powerpc::Relocate::relocate): Edit code using
	GOT16_HA, GOT16_LO_DS, and GOT_PCREL34 relocs.
This commit is contained in:
Alan Modra 2019-06-26 22:08:54 +09:30
parent e4dff7651b
commit c9b8abb7af
2 changed files with 104 additions and 11 deletions
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7
gold/ChangeLog
View File

@ -1,3 +1,10 @@
2019-07-13 Alan Modra <amodra@gmail.com>
* powerpc.cc (Powerpc_relobj::make_got_relative): New function.
(relative_value_is_known): New functions.
(Target_powerpc::Relocate::relocate): Edit code using
GOT16_HA, GOT16_LO_DS, and GOT_PCREL34 relocs.
2019-07-13 Alan Modra <amodra@gmail.com>
* powerpc.cc (Target_powerpc): Add powerxx_stubs_ and accessor

108
gold/powerpc.cc
View File

@ -249,6 +249,12 @@ public:
make_toc_relative(Target_powerpc<size, big_endian>* target,
Address* value);
bool
make_got_relative(Target_powerpc<size, big_endian>* target,
const Symbol_value<size>* psymval,
Address addend,
Address* value);
// Perform the Sized_relobj_file method, then set up opd info from
// .opd relocs.
void
@ -2387,6 +2393,25 @@ Powerpc_relobj<size, big_endian>::make_toc_relative(
return true;
}
template<int size, bool big_endian>
bool
Powerpc_relobj<size, big_endian>::make_got_relative(
Target_powerpc<size, big_endian>* target,
const Symbol_value<size>* psymval,
Address addend,
Address* value)
{
Address addr = psymval->value(this, addend);
Address got_base = (target->got_section()->output_section()->address()
+ this->toc_base_offset());
addr -= got_base;
if (addr + 0x80008000 > 0xffffffff)
return false;
*value = addr;
return true;
}
// Perform the Sized_relobj_file method, then set up opd info from
// .opd relocs.
@ -9660,6 +9685,37 @@ Target_powerpc<size, big_endian>::symval_for_branch(
return true;
}
template<int size>
static bool
relative_value_is_known(const Sized_symbol<size>* gsym)
{
if (gsym->type() == elfcpp::STT_GNU_IFUNC)
return false;
if (gsym->is_from_dynobj()
|| gsym->is_undefined()
|| gsym->is_preemptible())
return false;
if (gsym->is_absolute())
return !parameters->options().output_is_position_independent();
return true;
}
template<int size>
static bool
relative_value_is_known(const Symbol_value<size>* psymval)
{
if (psymval->is_ifunc_symbol())
return false;
bool is_ordinary;
unsigned int shndx = psymval->input_shndx(&is_ordinary);
return is_ordinary && shndx != elfcpp::SHN_UNDEF;
}
// Perform a relocation.
template<int size, bool big_endian>
@ -10446,7 +10502,10 @@ Target_powerpc<size, big_endian>::Relocate::relocate(
break;
}
if (size == 64)
if (size == 64
&& (gsym
? relative_value_is_known(gsym)
: relative_value_is_known(psymval)))
{
switch (r_type)
{
@ -10460,12 +10519,6 @@ Target_powerpc<size, big_endian>::Relocate::relocate(
// and
// addis ra,r2,0; addi rb,ra,x@toc@l;
// to nop; addi rb,r2,x@toc;
// FIXME: the @got sequence shown above is not yet
// optimized. Note that gcc as of 2017-01-07 doesn't use
// the ELF @got relocs except for TLS, instead using the
// PowerOpen variant of a compiler managed GOT (called TOC).
// The PowerOpen TOC sequence equivalent to the first
// example is optimized.
case elfcpp::R_POWERPC_GOT_TLSLD16_HA:
case elfcpp::R_POWERPC_GOT_TLSGD16_HA:
case elfcpp::R_POWERPC_GOT_TPREL16_HA:
@ -10476,8 +10529,12 @@ Target_powerpc<size, big_endian>::Relocate::relocate(
{
Insn* iview = reinterpret_cast<Insn*>(view - d_offset);
Insn insn = elfcpp::Swap<32, big_endian>::readval(iview);
if (r_type == elfcpp::R_PPC64_TOC16_HA
&& object->make_toc_relative(target, &value))
if ((r_type == elfcpp::R_PPC64_TOC16_HA
&& object->make_toc_relative(target, &value))
|| (r_type == elfcpp::R_POWERPC_GOT16_HA
&& object->make_got_relative(target, psymval,
rela.get_r_addend(),
&value)))
{
gold_assert((insn & ((0x3f << 26) | 0x1f << 16))
== ((15u << 26) | (2 << 16)));
@ -10505,8 +10562,12 @@ Target_powerpc<size, big_endian>::Relocate::relocate(
Insn* iview = reinterpret_cast<Insn*>(view - d_offset);
Insn insn = elfcpp::Swap<32, big_endian>::readval(iview);
bool changed = false;
if (r_type == elfcpp::R_PPC64_TOC16_LO_DS
&& object->make_toc_relative(target, &value))
if ((r_type == elfcpp::R_PPC64_TOC16_LO_DS
&& object->make_toc_relative(target, &value))
|| (r_type == elfcpp::R_PPC64_GOT16_LO_DS
&& object->make_got_relative(target, psymval,
rela.get_r_addend(),
&value)))
{
gold_assert ((insn & (0x3f << 26)) == 58u << 26 /* ld */);
insn ^= (14u << 26) ^ (58u << 26);
@ -10534,6 +10595,31 @@ Target_powerpc<size, big_endian>::Relocate::relocate(
}
break;
case elfcpp::R_PPC64_GOT_PCREL34:
if (parameters->options().toc_optimize())
{
Insn* iview = reinterpret_cast<Insn*>(view);
uint64_t insn = elfcpp::Swap<32, big_endian>::readval(iview);
insn <<= 32;
insn |= elfcpp::Swap<32, big_endian>::readval(iview + 1);
if ((insn & ((-1ULL << 50) | (63ULL << 26)))
!= ((1ULL << 58) | (1ULL << 52) | (57ULL << 26) /* pld */))
break;
Address relval = psymval->value(object, rela.get_r_addend());
relval -= address;
if (relval + (1ULL << 33) < 1ULL << 34)
{
value = relval;
// Replace with paddi
insn += (2ULL << 56) + (14ULL << 26) - (57ULL << 26);
elfcpp::Swap<32, big_endian>::writeval(iview, insn >> 32);
elfcpp::Swap<32, big_endian>::writeval(iview + 1,
insn & 0xffffffff);
}
}
break;
case elfcpp::R_POWERPC_TPREL16_HA:
if (parameters->options().tls_optimize() && value + 0x8000 < 0x10000)
{