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authorAlan Modra <amodra@gmail.com>2015-03-25 15:53:47 +1030
committerAlan Modra <amodra@gmail.com>2015-03-25 15:53:47 +1030
commitafcd9480feca651eef436d8438b783dde5c3bbb2 (patch)
tree97bd1be08268c51e674154d3bf98af3a2256c6f8 /sysdeps/powerpc/Makefile
parentda9f3334106ee0f98c499c54bdfe3c4fcbb348f4 (diff)
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powerpc __tls_get_addr call optimization
This patch is glibc support for a PowerPC TLS optimization, inspired
by Alexandre Oliva's TLS optimization for other processors,
http://www.lsd.ic.unicamp.br/~oliva/writeups/TLS/RFC-TLSDESC-x86.txt

In essence, this optimization uses a zero module id in the tls_index
GOT entry to indicate that a TLS variable is allocated space in the
static TLS area.  A special plt call linker stub for __tls_get_addr
checks for such a tls_index and if found, returns the offset
immediately.  The linker communicates the fact that the special
__tls_get_addr stub is used by setting a bit in the dynamic tag
DT_PPC64_OPT/DT_PPC_OPT.  glibc communicates to the linker that this
optimization is available by the presence of __tls_get_addr_opt.

tst-tlsmod2.so is built with -Wl,--no-tls-get-addr-optimize for
tst-tls-dlinfo, which otherwise would fail since it tests that no
static tls is allocated.  The ld option --no-tls-get-addr-optimize has
been available since binutils-2.20 so doesn't need a configure test.

	* NEWS: Advertise TLS optimization.
	* elf/elf.h (R_PPC_TLSGD, R_PPC_TLSLD, DT_PPC_OPT, PPC_OPT_TLS): Define.
	(DT_PPC_NUM): Increment.
	* elf/dynamic-link.h (HAVE_STATIC_TLS): Define.
	(CHECK_STATIC_TLS): Use here.
	* sysdeps/powerpc/powerpc32/dl-machine.h (elf_machine_rela): Optimize
	TLS descriptors.
	* sysdeps/powerpc/powerpc64/dl-machine.h (elf_machine_rela): Likewise.
	* sysdeps/powerpc/dl-tls.c: New file.
	* sysdeps/powerpc/Versions: Add __tls_get_addr_opt.
	* sysdeps/powerpc/tst-tlsopt-powerpc.c: New tls test.
	* sysdeps/unix/sysv/linux/powerpc/Makefile: Add new test.
	Build tst-tlsmod2.so with --no-tls-get-addr-optimize.
	* sysdeps/unix/sysv/linux/powerpc/powerpc32/ld.abilist: Update.
	* sysdeps/unix/sysv/linux/powerpc/powerpc64/ld.abilist: Likewise.
	* sysdeps/unix/sysv/linux/powerpc/powerpc64/ld-le.abilist: Likewise.
Diffstat (limited to 'sysdeps/powerpc/Makefile')
-rw-r--r--sysdeps/powerpc/Makefile3
1 files changed, 3 insertions, 0 deletions
diff --git a/sysdeps/powerpc/Makefile b/sysdeps/powerpc/Makefile
index b11edd77bd..533d763915 100644
--- a/sysdeps/powerpc/Makefile
+++ b/sysdeps/powerpc/Makefile
@@ -8,6 +8,9 @@ sysdep-dl-routines += dl-machine
 sysdep_routines += dl-machine
 # extra shared linker files to link only into dl-allobjs.so
 sysdep-rtld-routines += dl-machine
+# Don't optimize GD tls sequence to LE.
+LDFLAGS-tst-tlsopt-powerpc += -Wl,--no-tls-optimize
+tests += tst-tlsopt-powerpc
 endif
 
 ifeq ($(subdir),setjmp)