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PowerPC64 --plt-align

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This changes the PowerPC64 --plt-align option to perform the usual
alignment of code as suggested by its name, as well as the previous
behaviour of padding so as to reduce boundary crossing.  The old
behaviour is had by using a negative parameter.

The default is also changed to align plt stub code by default to 32
byte boundaries, the point being to get better bctr branch prediction
on power8 and power9 hardware.

bfd/
	* elf64-ppp.c (plt_stub_pad): Handle positive and negative
	plt_stub_align.
ld/
	* ld.texinfo (--plt-align): Describe new behaviour of option.
	* emultempl/ppc64elf.em (params): Default plt_stub_align to 5.
	* testsuite/ld-powerpc/powerpc.exp: Pass --no-plt-align for
	selected tests.
	* testsuite/ld-powerpc/relbrlt.d: Pass --no-plt-align.
	* testsuite/ld-powerpc/elfv2so.d: Adjust expected output.
This commit is contained in:
Alan Modra 2017-09-09 21:55:22 +09:30
parent c5bce5c697
commit 2420fff633
8 changed files with 55 additions and 22 deletions
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5
bfd/ChangeLog
View File

@ -1,3 +1,8 @@
2017-09-09 Alan Modra <amodra@gmail.com>
* elf64-ppp.c (plt_stub_pad): Handle positive and negative
plt_stub_align.
2017-09-09 H.J. Lu <hongjiu.lu@intel.com>
* elf32-i386.c (elf_i386_relocate_section): Update usage of

19
bfd/elf64-ppc.c
View File

@ -10610,17 +10610,30 @@ plt_stub_size (struct ppc_link_hash_table *htab,
return size;
}
/* If this stub would cross fewer 2**plt_stub_align boundaries if we align,
then return the padding needed to do so. */
/* Depending on the sign of plt_stub_align:
If positive, return the padding to align to a 2**plt_stub_align
boundary.
If negative, if this stub would cross fewer 2**plt_stub_align
boundaries if we align, then return the padding needed to do so. */
static inline unsigned int
plt_stub_pad (struct ppc_link_hash_table *htab,
struct ppc_stub_hash_entry *stub_entry,
bfd_vma plt_off)
{
int stub_align = 1 << htab->params->plt_stub_align;
int stub_align;
unsigned stub_size = plt_stub_size (htab, stub_entry, plt_off);
bfd_vma stub_off = stub_entry->group->stub_sec->size;
if (htab->params->plt_stub_align >= 0)
{
stub_align = 1 << htab->params->plt_stub_align;
if ((stub_off & (stub_align - 1)) != 0)
return stub_align - (stub_off & (stub_align - 1));
return 0;
}
stub_align = 1 << -htab->params->plt_stub_align;
if (((stub_off + stub_size - 1) & -stub_align) - (stub_off & -stub_align)
> ((stub_size - 1) & -stub_align))
return stub_align - (stub_off & (stub_align - 1));

9
ld/ChangeLog
View File

@ -1,3 +1,12 @@
2017-09-09 Alan Modra <amodra@gmail.com>
* ld.texinfo (--plt-align): Describe new behaviour of option.
* emultempl/ppc64elf.em (params): Default plt_stub_align to 5.
* testsuite/ld-powerpc/powerpc.exp: Pass --no-plt-align for
selected tests.
* testsuite/ld-powerpc/relbrlt.d: Pass --no-plt-align.
* testsuite/ld-powerpc/elfv2so.d: Adjust expected output.
2017-09-09 H.J. Lu <hongjiu.lu@intel.com>
PR ld/22115

2
ld/emultempl/ppc64elf.em
View File

@ -37,7 +37,7 @@ static struct ppc64_elf_params params = { NULL,
&ppc_add_stub_section,
&ppc_layout_sections_again,
1, -1, 0,
${DEFAULT_PLT_STATIC_CHAIN-0}, -1, 0,
${DEFAULT_PLT_STATIC_CHAIN-0}, -1, 5,
-1, 0, -1, -1, 0};
/* Fake input file for stubs. */

10
ld/ld.texinfo
View File

@ -7603,10 +7603,12 @@ off this feature.
@item --plt-align
@itemx --no-plt-align
Use these options to control whether individual PLT call stubs are
padded so that they don't cross a 32-byte boundary, or to the
specified power of two boundary when using @code{--plt-align=}. Note
that this isn't alignment in the usual sense. By default PLT call
stubs are packed tightly.
aligned to a 32-byte boundary, or to the specified power of two
boundary when using @code{--plt-align=}. A negative value may be
specified to pad PLT call stubs so that they do not cross the
specified power of two boundary (or the minimum number of boundaries
if a PLT stub is so large that it must cross a boundary). By default
PLT call stubs are aligned to 32-byte boundaries.
@cindex PowerPC64 PLT call stub static chain
@kindex --plt-static-chain

12
ld/testsuite/ld-powerpc/elfv2so.d
View File

@ -12,24 +12,28 @@ Disassembly of section \.text:
.*: (e9 82 80 38|38 80 82 e9) ld r12,-32712\(r2\)
.*: (7d 89 03 a6|a6 03 89 7d) mtctr r12
.*: (4e 80 04 20|20 04 80 4e) bctr
\.\.\.
.* <.*\.plt_call\.f3>:
.*: (f8 41 00 18|18 00 41 f8) std r2,24\(r1\)
.*: (e9 82 80 28|28 80 82 e9) ld r12,-32728\(r2\)
.*: (7d 89 03 a6|a6 03 89 7d) mtctr r12
.*: (4e 80 04 20|20 04 80 4e) bctr
\.\.\.
.* <.*\.plt_call\.f2>:
.*: (f8 41 00 18|18 00 41 f8) std r2,24\(r1\)
.*: (e9 82 80 30|30 80 82 e9) ld r12,-32720\(r2\)
.*: (7d 89 03 a6|a6 03 89 7d) mtctr r12
.*: (4e 80 04 20|20 04 80 4e) bctr
\.\.\.
.* <.*\.plt_call\.f1>:
.*: (f8 41 00 18|18 00 41 f8) std r2,24\(r1\)
.*: (e9 82 80 40|40 80 82 e9) ld r12,-32704\(r2\)
.*: (7d 89 03 a6|a6 03 89 7d) mtctr r12
.*: (4e 80 04 20|20 04 80 4e) bctr
\.\.\.
.* <f1>:
.*: (3c 4c 00 02|02 00 4c 3c) addis r2,r12,2
@ -37,14 +41,14 @@ Disassembly of section \.text:
.*: (7c 08 02 a6|a6 02 08 7c) mflr r0
.*: (f8 21 ff e1|e1 ff 21 f8) stdu r1,-32\(r1\)
.*: (f8 01 00 30|30 00 01 f8) std r0,48\(r1\)
.*: (4b ff ff dd|dd ff ff 4b) bl .*\.plt_call\.f1>
.*: (4b ff ff cd|cd ff ff 4b) bl .*\.plt_call\.f1>
.*: (e8 62 80 08|08 80 62 e8) ld r3,-32760\(r2\)
.*: (4b ff ff c5|c5 ff ff 4b) bl .*\.plt_call\.f2>
.*: (4b ff ff a5|a5 ff ff 4b) bl .*\.plt_call\.f2>
.*: (e8 41 00 18|18 00 41 e8) ld r2,24\(r1\)
.*: (e8 62 80 10|10 80 62 e8) ld r3,-32752\(r2\)
.*: (4b ff ff a9|a9 ff ff 4b) bl .*\.plt_call\.f3>
.*: (4b ff ff 79|79 ff ff 4b) bl .*\.plt_call\.f3>
.*: (e8 41 00 18|18 00 41 e8) ld r2,24\(r1\)
.*: (4b ff ff 91|91 ff ff 4b) bl .*\.plt_call\.f4>
.*: (4b ff ff 51|51 ff ff 4b) bl .*\.plt_call\.f4>
.*: (e8 41 00 18|18 00 41 e8) ld r2,24\(r1\)
.*: (e8 01 00 30|30 00 01 e8) ld r0,48\(r1\)
.*: (38 21 00 20|20 00 21 38) addi r1,r1,32

18
ld/testsuite/ld-powerpc/powerpc.exp
View File

@ -163,26 +163,26 @@ set ppcelftests {
}
set ppc64elftests {
{"TLS static exec (markers)" "-melf64ppc" ""
{"TLS static exec (markers)" "-melf64ppc --no-plt-align" ""
"-a64 --defsym TLSMARK=1" {tls.s tlslib.s}
{{objdump -dr tls.d} {objdump -sj.got tls.g} {objdump -sj.tdata tls.t}}
"tlsm"}
{"TLS static exec" "-melf64ppc" "" "-a64" {tls.s tlslib.s}
{"TLS static exec" "-melf64ppc --no-plt-align" "" "-a64" {tls.s tlslib.s}
{{objdump -dr tls.d} {objdump -sj.got tls.g} {objdump -sj.tdata tls.t}}
"tls"}
{"TLS helper shared library" "-shared -melf64ppc tmpdir/tlslib.o" "" "" {}
{} "libtlslib.so"}
{"TLS helper old shared lib" "-shared -melf64ppc" "" "-a64" {oldtlslib.s}
{} "liboldlib.so"}
{"TLS dynamic exec" "-melf64ppc --no-ld-generated-unwind-info --hash-style=sysv tmpdir/tls.o tmpdir/libtlslib.so" "" "" {}
{"TLS dynamic exec" "-melf64ppc --no-plt-align --no-ld-generated-unwind-info --hash-style=sysv tmpdir/tls.o tmpdir/libtlslib.so" "" "" {}
{{readelf -WSsrl tlsexe.r} {objdump -dr tlsexe.d}
{objdump -sj.got tlsexe.g} {objdump -sj.tdata tlsexe.t}}
"tlsexe"}
{"TLS dynamic old" "-melf64ppc --no-ld-generated-unwind-info --hash-style=sysv tmpdir/tls.o tmpdir/liboldlib.so" "" "" {}
{"TLS dynamic old" "-melf64ppc --no-plt-align --no-ld-generated-unwind-info --hash-style=sysv tmpdir/tls.o tmpdir/liboldlib.so" "" "" {}
{{readelf -WSsrl tlsexe.r} {objdump -dr tlsexe.d}
{objdump -sj.got tlsexe.g} {objdump -sj.tdata tlsexe.t}}
"tlsexeold"}
{"TLS shared" "-shared -melf64ppc --no-ld-generated-unwind-info --hash-style=sysv tmpdir/tls.o" "" "" {}
{"TLS shared" "-shared -melf64ppc --no-plt-align --no-ld-generated-unwind-info --hash-style=sysv tmpdir/tls.o" "" "" {}
{{readelf -WSsrl tlsso.r} {objdump -dr tlsso.d}
{objdump -sj.got tlsso.g} {objdump -sj.tdata tlsso.t}}
"tls.so"}
@ -190,17 +190,17 @@ set ppc64elftests {
{{objdump -dr tlstoc.d} {objdump -sj.got tlstoc.g}
{objdump -sj.tdata tlstoc.t}}
"tlstoc"}
{"TLSTOC dynamic exec" "-melf64ppc --no-ld-generated-unwind-info --hash-style=sysv tmpdir/tlstoc.o tmpdir/libtlslib.so" ""
{"TLSTOC dynamic exec" "-melf64ppc --no-plt-align --no-ld-generated-unwind-info --hash-style=sysv tmpdir/tlstoc.o tmpdir/libtlslib.so" ""
"" {}
{{readelf -WSsrl tlsexetoc.r} {objdump -dr tlsexetoc.d}
{objdump -sj.got tlsexetoc.g} {objdump -sj.tdata tlsexetoc.t}}
"tlsexetoc"}
{"TLSTOC dynamic old" "-melf64ppc --no-ld-generated-unwind-info --hash-style=sysv tmpdir/tlstoc.o tmpdir/liboldlib.so" ""
{"TLSTOC dynamic old" "-melf64ppc --no-plt-align --no-ld-generated-unwind-info --hash-style=sysv tmpdir/tlstoc.o tmpdir/liboldlib.so" ""
"" {}
{{readelf -WSsrl tlsexetoc.r} {objdump -dr tlsexetoc.d}
{objdump -sj.got tlsexetoc.g} {objdump -sj.tdata tlsexetoc.t}}
"tlsexetocold"}
{"TLSTOC shared" "-shared -melf64ppc --no-ld-generated-unwind-info --hash-style=sysv tmpdir/tlstoc.o" "" "" {}
{"TLSTOC shared" "-shared -melf64ppc --no-plt-align --no-ld-generated-unwind-info --hash-style=sysv tmpdir/tlstoc.o" "" "" {}
{{readelf -WSsrl tlstocso.r} {objdump -dr tlstocso.d}
{objdump -sj.got tlstocso.g} {objdump -sj.tdata tlstocso.t}}
"tlstoc.so"}
@ -221,7 +221,7 @@ set ppc64elftests {
"tlsopt4"}
{"TLS DLL" "-shared -melf64ppc --version-script tlsdll.ver" "" "-a64" {tlsdll.s}
{} "tlsdll.so"}
{"TLS opt 5" "-melf64ppc -shared --gc-sections --no-plt-localentry tmpdir/tlsdll.so" "" "-a64" {tlsopt5.s}
{"TLS opt 5" "-melf64ppc --no-plt-align -shared --gc-sections --no-plt-localentry tmpdir/tlsdll.so" "" "-a64" {tlsopt5.s}
{{objdump -dr tlsopt5.d} {readelf -wf tlsopt5.wf}}
"tlsopt5"}
{"sym@tocbase" "-shared -melf64ppc" "" "-a64" {symtocbase-1.s symtocbase-2.s}

2
ld/testsuite/ld-powerpc/relbrlt.d
View File

@ -1,6 +1,6 @@
#source: relbrlt.s
#as: -a64
#ld: -melf64ppc --no-ld-generated-unwind-info --emit-relocs
#ld: -melf64ppc --no-plt-align --no-ld-generated-unwind-info --emit-relocs
#objdump: -Dr
.*