powerpc __tls_get_addr call optimization

[Alan Modra <amodra at gmail dot com>]

Now that Alex's fixes for static TLS have gone in, I figure it's worth
revisiting an old patch of mine.
https://sourceware.org/ml/libc-alpha/2009-03/msg00053.html

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
descriptor 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 descriptor and if found, returns the offset
immediately.  The linker communicates the fact that the special
__tls_get_addr stub is present by setting a bit in the dynamic tag
DT_PPC64_OPT/DT_PPC_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.

Regression tested powerpc-linux and powerpc64-linux.

	* 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, extracted from..
	(CHECK_STATIC_TLS): ..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/unix/sysv/linux/powerpc/Makefile: 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.

diff --git a/NEWS b/NEWS
index 86394b8..a6a8b6d 100644
--- a/NEWS
+++ b/NEWS
@@ -17,6 +17,9 @@ Version 2.22
   18042, 18043, 18046, 18047, 18068, 18080, 18093, 18104, 18110, 18111,
   18128.
 
+* A powerpc and powerpc64 optimization for TLS, similar to TLS descriptors
+  for LD and GD on x86 and x86-64, has been implemented.
+
 * Character encoding and ctype tables were updated to Unicode 7.0.0, using
   new generator scripts contributed by Pravin Satpute and Mike FABIAN (Red
   Hat).  These updates cause user visible changes, such as the fix for bug
diff --git a/elf/dynamic-link.h b/elf/dynamic-link.h
index 6f4a773..8d428e2 100644
--- a/elf/dynamic-link.h
+++ b/elf/dynamic-link.h
@@ -25,11 +25,14 @@
    an attempt to allocate it in surplus space on the fly.  If that
    can't be done, we fall back to the error that DF_STATIC_TLS is
    intended to produce.  */
+#define HAVE_STATIC_TLS(map, sym_map)					\
+    (__builtin_expect ((sym_map)->l_tls_offset != NO_TLS_OFFSET		\
+		       && ((sym_map)->l_tls_offset			\
+			   != FORCED_DYNAMIC_TLS_OFFSET), 1))
+
 #define CHECK_STATIC_TLS(map, sym_map)					\
     do {								\
-      if (__builtin_expect ((sym_map)->l_tls_offset == NO_TLS_OFFSET	\
-			    || ((sym_map)->l_tls_offset			\
-				== FORCED_DYNAMIC_TLS_OFFSET), 0))	\
+      if (!HAVE_STATIC_TLS (map, sym_map))				\
 	_dl_allocate_static_tls (sym_map);				\
     } while (0)
 
diff --git a/elf/elf.h b/elf/elf.h
index 496f08d..71492a2 100644
--- a/elf/elf.h
+++ b/elf/elf.h
@@ -2194,6 +2194,8 @@ enum
 #define R_PPC_GOT_DTPREL16_LO	92 /* half16*	(sym+add)@got@dtprel@l */
 #define R_PPC_GOT_DTPREL16_HI	93 /* half16*	(sym+add)@got@dtprel@h */
 #define R_PPC_GOT_DTPREL16_HA	94 /* half16*	(sym+add)@got@dtprel@ha */
+#define R_PPC_TLSGD		95 /* none	(sym+add)@tlsgd */
+#define R_PPC_TLSLD		96 /* none	(sym+add)@tlsld */
 
 /* The remaining relocs are from the Embedded ELF ABI, and are not
    in the SVR4 ELF ABI.  */
@@ -2237,7 +2239,11 @@ enum
 
 /* PowerPC specific values for the Dyn d_tag field.  */
 #define DT_PPC_GOT		(DT_LOPROC + 0)
-#define DT_PPC_NUM		1
+#define DT_PPC_OPT		(DT_LOPROC + 1)
+#define DT_PPC_NUM		2
+
+/* PowerPC specific values for the DT_PPC_OPT Dyn entry.  */
+#define PPC_OPT_TLS		1
 
 /* PowerPC64 relocations defined by the ABIs */
 #define R_PPC64_NONE		R_PPC_NONE
diff --git a/sysdeps/powerpc/Versions b/sysdeps/powerpc/Versions
index 47c2c3e..2aebf7c 100644
--- a/sysdeps/powerpc/Versions
+++ b/sysdeps/powerpc/Versions
@@ -15,3 +15,9 @@ libc {
     __vmx__libc_longjmp; __vmx__libc_siglongjmp;
   }
 }
+
+ld {
+  GLIBC_2.22 {
+    __tls_get_addr_opt;
+  }
+}
diff --git a/sysdeps/powerpc/dl-tls.c b/sysdeps/powerpc/dl-tls.c
new file mode 100644
index 0000000..a18b23e
--- /dev/null
+++ b/sysdeps/powerpc/dl-tls.c
@@ -0,0 +1,24 @@
+/* Thread-local storage handling in the ELF dynamic linker.  PowerPC version.
+   Copyright (C) 2009-2015 Free Software Foundation, Inc.
+   This file is part of the GNU C Library.
+
+   The GNU C Library is free software; you can redistribute it and/or
+   modify it under the terms of the GNU Lesser General Public
+   License as published by the Free Software Foundation; either
+   version 2.1 of the License, or (at your option) any later version.
+
+   The GNU C Library is distributed in the hope that it will be useful,
+   but WITHOUT ANY WARRANTY; without even the implied warranty of
+   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+   Lesser General Public License for more details.
+
+   You should have received a copy of the GNU Lesser General Public
+   License along with the GNU C Library; if not, write to the Free
+   Software Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA
+   02111-1307 USA.  */
+
+#include "elf/dl-tls.c"
+
+#ifdef SHARED
+strong_alias(__tls_get_addr, __tls_get_addr_opt)
+#endif
diff --git a/sysdeps/powerpc/powerpc32/dl-machine.h b/sysdeps/powerpc/powerpc32/dl-machine.h
index c94674f..8b0c067 100644
--- a/sysdeps/powerpc/powerpc32/dl-machine.h
+++ b/sysdeps/powerpc/powerpc32/dl-machine.h
@@ -333,6 +333,32 @@ elf_machine_rela (struct link_map *map, const Elf32_Rela *reloc,
 # endif
 
     case R_PPC_DTPMOD32:
+      if (map->l_info[DT_PPC(OPT)]
+	  && (map->l_info[DT_PPC(OPT)]->d_un.d_val & PPC_OPT_TLS))
+	{
+	  if (!NOT_BOOTSTRAP)
+	    {
+	      reloc_addr[0] = 0;
+	      reloc_addr[1] = (sym_map->l_tls_offset - TLS_TP_OFFSET
+			       + TLS_DTV_OFFSET);
+	      break;
+	    }
+	  else if (sym_map != NULL)
+	    {
+# ifndef SHARED
+	      CHECK_STATIC_TLS (map, sym_map);
+# else
+	      if (TRY_STATIC_TLS (map, sym_map))
+# endif
+		{
+		  reloc_addr[0] = 0;
+		  /* Set up for local dynamic.  */
+		  reloc_addr[1] = (sym_map->l_tls_offset - TLS_TP_OFFSET
+				   + TLS_DTV_OFFSET);
+		  break;
+		}
+	    }
+	}
       if (!NOT_BOOTSTRAP)
 	/* During startup the dynamic linker is always index 1.  */
 	*reloc_addr = 1;
@@ -342,6 +368,28 @@ elf_machine_rela (struct link_map *map, const Elf32_Rela *reloc,
 	*reloc_addr = sym_map->l_tls_modid;
       break;
     case R_PPC_DTPREL32:
+      if (map->l_info[DT_PPC(OPT)]
+	  && (map->l_info[DT_PPC(OPT)]->d_un.d_val & PPC_OPT_TLS))
+	{
+	  if (!NOT_BOOTSTRAP)
+	    {
+	      *reloc_addr = TLS_TPREL_VALUE (sym_map, sym, reloc);
+	      break;
+	    }
+	  else if (sym_map != NULL)
+	    {
+	      /* This reloc is always preceded by R_PPC_DTPMOD32.  */
+# ifndef SHARED
+	      assert (HAVE_STATIC_TLS (map, sym_map));
+# else
+	      if (HAVE_STATIC_TLS (map, sym_map))
+# endif
+		{
+		  *reloc_addr = TLS_TPREL_VALUE (sym_map, sym, reloc);
+		  break;
+		}
+	    }
+	}
       /* During relocation all TLS symbols are defined and used.
 	 Therefore the offset is already correct.  */
       if (NOT_BOOTSTRAP && sym_map != NULL)
diff --git a/sysdeps/powerpc/powerpc64/dl-machine.h b/sysdeps/powerpc/powerpc64/dl-machine.h
index 5cb0087..55ac736 100644
--- a/sysdeps/powerpc/powerpc64/dl-machine.h
+++ b/sysdeps/powerpc/powerpc64/dl-machine.h
@@ -701,6 +701,32 @@ elf_machine_rela (struct link_map *map,
       return;
 
     case R_PPC64_DTPMOD64:
+      if (map->l_info[DT_PPC64(OPT)]
+	  && (map->l_info[DT_PPC64(OPT)]->d_un.d_val & PPC64_OPT_TLS))
+	{
+#ifdef RTLD_BOOTSTRAP
+	  reloc_addr[0] = 0;
+	  reloc_addr[1] = (sym_map->l_tls_offset - TLS_TP_OFFSET
+			   + TLS_DTV_OFFSET);
+	  return;
+#else
+	  if (sym_map != NULL)
+	    {
+# ifndef SHARED
+	      CHECK_STATIC_TLS (map, sym_map);
+# else
+	      if (TRY_STATIC_TLS (map, sym_map))
+# endif
+		{
+		  reloc_addr[0] = 0;
+		  /* Set up for local dynamic.  */
+		  reloc_addr[1] = (sym_map->l_tls_offset - TLS_TP_OFFSET
+				   + TLS_DTV_OFFSET);
+		  return;
+		}
+	    }
+#endif
+	}
 #ifdef RTLD_BOOTSTRAP
       /* During startup the dynamic linker is always index 1.  */
       *reloc_addr = 1;
@@ -713,6 +739,28 @@ elf_machine_rela (struct link_map *map,
       return;
 
     case R_PPC64_DTPREL64:
+      if (map->l_info[DT_PPC64(OPT)]
+	  && (map->l_info[DT_PPC64(OPT)]->d_un.d_val & PPC64_OPT_TLS))
+	{
+#ifdef RTLD_BOOTSTRAP
+	  *reloc_addr = TLS_TPREL_VALUE (sym_map, sym, reloc);
+	  return;
+#else
+	  if (sym_map != NULL)
+	    {
+	      /* This reloc is always preceded by R_PPC64_DTPMOD64.  */
+# ifndef SHARED
+	      assert (HAVE_STATIC_TLS (map, sym_map));
+# else
+	      if (HAVE_STATIC_TLS (map, sym_map))
+#  endif
+		{
+		  *reloc_addr = TLS_TPREL_VALUE (sym_map, sym, reloc);
+		  return;
+		}
+	    }
+#endif
+	}
       /* During relocation all TLS symbols are defined and used.
 	 Therefore the offset is already correct.  */
 #ifndef RTLD_BOOTSTRAP
diff --git a/sysdeps/unix/sysv/linux/powerpc/Makefile b/sysdeps/unix/sysv/linux/powerpc/Makefile
index fcf3bb5..c89ed9e 100644
--- a/sysdeps/unix/sysv/linux/powerpc/Makefile
+++ b/sysdeps/unix/sysv/linux/powerpc/Makefile
@@ -20,6 +20,8 @@ ifeq ($(build-shared),yes)
 # This is needed for DSO loading from static binaries.
 sysdep-dl-routines += dl-static
 endif
+# Otherwise tst-tls-dlinfo fails due to tst-tlsmod2.so using static tls.
+LDFLAGS-tst-tlsmod2.so += -Wl,--no-tls-get-addr-optimize
 endif
 
 ifeq ($(subdir),misc)
diff --git a/sysdeps/unix/sysv/linux/powerpc/powerpc32/ld.abilist b/sysdeps/unix/sysv/linux/powerpc/powerpc32/ld.abilist
index d71611f..052f311 100644
--- a/sysdeps/unix/sysv/linux/powerpc/powerpc32/ld.abilist
+++ b/sysdeps/unix/sysv/linux/powerpc/powerpc32/ld.abilist
@@ -1,3 +1,6 @@
+GLIBC_2.22
+ GLIBC_2.22 A
+ __tls_get_addr_opt F
 GLIBC_2.0
  GLIBC_2.0 A
  __libc_memalign F
diff --git a/sysdeps/unix/sysv/linux/powerpc/powerpc64/ld-le.abilist b/sysdeps/unix/sysv/linux/powerpc/powerpc64/ld-le.abilist
index 3530fb4..3174e21 100644
--- a/sysdeps/unix/sysv/linux/powerpc/powerpc64/ld-le.abilist
+++ b/sysdeps/unix/sysv/linux/powerpc/powerpc64/ld-le.abilist
@@ -9,3 +9,6 @@ GLIBC_2.17
  free F
  malloc F
  realloc F
+GLIBC_2.22
+ GLIBC_2.22 A
+ __tls_get_addr_opt F
diff --git a/sysdeps/unix/sysv/linux/powerpc/powerpc64/ld.abilist b/sysdeps/unix/sysv/linux/powerpc/powerpc64/ld.abilist
index 899360e..d8c4201 100644
--- a/sysdeps/unix/sysv/linux/powerpc/powerpc64/ld.abilist
+++ b/sysdeps/unix/sysv/linux/powerpc/powerpc64/ld.abilist
@@ -1,3 +1,6 @@
+GLIBC_2.22
+ GLIBC_2.22 A
+ __tls_get_addr_opt F
 GLIBC_2.3
  GLIBC_2.3 A
  __libc_memalign F

-- 
Alan Modra
Australia Development Lab, IBM