[PATCHv2] powerpc64: Implement TLS using PC-relative addressing

[Tulio Magno Quites Machado Filho <tuliom@linux.ibm.com>]

Changes since v1:
 - Dropped the workaround for early GCC 10 versions.  We can't get this
   code to work without having the macro __PCREL__.  The previous code
   was failing if -mcpu=power10 -mno-pcrel was used.
 - Fixed coding style issues (added space after #defined and removed
   unnecessary parenthesis).

---8<---

As the TOC pointer becomes optional on POWER, TLS access has to be
modified in order to use PC-relative addressing instead of depending on
the TOC pointer availability.

This patch also changes old TLS code to use the new syntax.  It's a
purely aesthetical change: the old code still works and the new syntax
helps to move the argument setup instruction away from the call, which
is not used in an inline assembly.

Suggested-by: Alan Modra <amodra@gmail.com>
---
 sysdeps/powerpc/mod-tlsopt-powerpc.c   |  7 ++++
 sysdeps/powerpc/powerpc64/tls-macros.h | 54 ++++++++++++++++++++++----
 2 files changed, 53 insertions(+), 8 deletions(-)

diff --git a/sysdeps/powerpc/mod-tlsopt-powerpc.c b/sysdeps/powerpc/mod-tlsopt-powerpc.c
index ee0db12a73..ecfa11cb95 100644
--- a/sysdeps/powerpc/mod-tlsopt-powerpc.c
+++ b/sysdeps/powerpc/mod-tlsopt-powerpc.c
@@ -24,7 +24,14 @@ tls_get_addr_opt_test (void)
   tls_index *tls_arg;
 #ifdef __powerpc64__
   register unsigned long thread_pointer __asm__ ("r13");
+  /* PC-relative addressing is available when compiling with -mpcrel.
+     The first releases of GCC 10 do support -mpcrel, but do not export
+     __PCREL__.  */
+# if defined __PCREL__
+  asm ("pla %0,foo@got@tlsgd@pcrel" : "=r" (tls_arg));
+# else
   asm ("addi %0,2,foo@got@tlsgd" : "=r" (tls_arg));
+# endif
 #else
   register unsigned long thread_pointer __asm__ ("r2");
   asm ("bcl 20,31,1f\n1:\t"
diff --git a/sysdeps/powerpc/powerpc64/tls-macros.h b/sysdeps/powerpc/powerpc64/tls-macros.h
index 79a0b2579c..a0e5c4a832 100644
--- a/sysdeps/powerpc/powerpc64/tls-macros.h
+++ b/sysdeps/powerpc/powerpc64/tls-macros.h
@@ -9,20 +9,56 @@
 	  : "=b" (__result) );						      \
      __result;								      \
   })
-/* PowerPC64 Initial Exec TLS access.  */
-#define TLS_IE(x)							      \
+
+/* PC-relative addressing is available when compiling with -mpcrel.
+   The first releases of GCC 10 do support -mpcrel, but do not export
+   __PCREL__.  */
+#if defined __PCREL__
+/* PowerPC64 Initial Exec TLS access, PC-relative addressing.  */
+# define TLS_IE(x)							      \
   ({ int * __result;							      \
-     asm ("ld  %0," #x "@got@tprel(2)\n\t"				      \
-	  "add %0,%0," #x "@tls"					      \
+     asm ("pld  %0," #x "@got@tprel@pcrel\n\t"				      \
+	  "add %0,%0," #x "@tls@pcrel"					      \
 	  : "=r" (__result) );						      \
      __result;								      \
   })
 
+/* PowerPC64 Local Dynamic TLS access, PC-relative addressing.  */
+# define TLS_LD(x)							      \
+  ({ int * __result;							      \
+     asm ("pla   3, " #x "@got@tlsld@pcrel\n\t"				      \
+	  "bl    __tls_get_addr@notoc(" #x "@tlsld)\n\t"		      \
+	  "addis %0,3," #x "@dtprel@ha\n\t"				      \
+	  "addi  %0,%0," #x "@dtprel@l"					      \
+	  : "=b" (__result) :						      \
+	  : "3", __TLS_CALL_CLOBBERS);					      \
+     __result;								      \
+  })
+
+/* PowerPC64 General Dynamic TLS access, PC-relative addressing.  */
+# define TLS_GD(x)							      \
+  ({ register int *__result __asm__ ("r3");				      \
+    asm ("pla   3," #x "@got@tlsgd@pcrel\n\t"				      \
+	 "bl    __tls_get_addr@notoc(" #x "@tlsgd)"			      \
+	 : "=r" (__result) :						      \
+	 : __TLS_CALL_CLOBBERS);					      \
+    __result;								      \
+  })
+#else
+/* PowerPC64 Initial Exec TLS access.  */
+# define TLS_IE(x)							      \
+  ({ int * __result;							      \
+    asm ("ld  %0," #x "@got@tprel(2)\n\t"				      \
+	 "add %0,%0," #x "@tls"						      \
+	 : "=r" (__result) );						      \
+    __result;								      \
+  })
+
 /* PowerPC64 Local Dynamic TLS access.  */
-#define TLS_LD(x)							      \
+# define TLS_LD(x)							      \
   ({ int * __result;							      \
      asm ("addi  3,2," #x "@got@tlsld\n\t"				      \
-	  "bl    __tls_get_addr\n\t"					      \
+	  "bl    __tls_get_addr(" #x "@tlsld)\n\t"			      \
 	  "nop   \n\t"							      \
 	  "addis %0,3," #x "@dtprel@ha\n\t"				      \
 	  "addi  %0,%0," #x "@dtprel@l"					      \
@@ -30,13 +66,15 @@
 	  : "3", __TLS_CALL_CLOBBERS);					      \
      __result;								      \
   })
+
 /* PowerPC64 General Dynamic TLS access.  */
-#define TLS_GD(x)							      \
+# define TLS_GD(x)							      \
   ({ register int *__result __asm__ ("r3");				      \
      asm ("addi  3,2," #x "@got@tlsgd\n\t"				      \
-	  "bl    __tls_get_addr\n\t"					      \
+	  "bl    __tls_get_addr(" #x "@tlsgd)\n\t"			      \
 	  "nop   "							      \
 	  : "=r" (__result) :						      \
 	  : __TLS_CALL_CLOBBERS);					      \
      __result;								      \
   })
+#endif
-- 
2.29.2