[PATCHv2] powerpc64: Implement TLS using PC-relative addressing
Commit Message
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(-)
Comments
Tulio Magno Quites Machado Filho via Libc-alpha <libc-alpha@sourceware.org> writes:
> 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>
Adhemerval,
I've just realized I forgot to Cc you in this patch.
It's fixing test failures when building glibc using --with-cpu=power10.
May we merge it for 2.33?
On 21/01/2021 22:29, Tulio Magno Quites Machado Filho via Libc-alpha wrote:
> 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"
The 'pla/pld' instruction support was added in binutils 2.33 version
(PowerPC D-form prefixed loads and stores, commit 8acf14351c8),
however the current idea is to set the minimal version for powerpc
to 2.29 [1].
The tls-macros.h is used solely for testing and if I understood
correctly -mpcrel should not require extra glibc support (so there
is no compiling reason to increase the current proposal of minimal
binutils to 2.33).
So, what I recommend you to do is:
1. Change the documentation patch [1] and update the powerpc
sysdeps/powerpc/powerpc64/le/configure.ac to check 'as' version
instead of 'objcopy'.
2. Add a configure check for the new TLS using PC-relative and
set a new config.h flag (SUPPORT_PPC_TLS_PCREL).
3. Use it instead of __PCREL__ on internal testing.
[1] https://sourceware.org/pipermail/libc-alpha/2021-January/121919.html
> 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
>
Adhemerval Zanella via Libc-alpha <libc-alpha@sourceware.org> writes:
> On 21/01/2021 22:29, Tulio Magno Quites Machado Filho via Libc-alpha wrote:
> So, what I recommend you to do is:
>
> 1. Change the documentation patch [1] and update the powerpc
> sysdeps/powerpc/powerpc64/le/configure.ac to check 'as' version
> instead of 'objcopy'.
This has already been changed in the following patch:
https://sourceware.org/pipermail/libc-alpha/2021-January/121919.html
It's still missing the configure check, though. I'm working on that.
> 2. Add a configure check for the new TLS using PC-relative and
> set a new config.h flag (SUPPORT_PPC_TLS_PCREL).
Ack. I'm working on it.
Thanks!
On Mon, Jan 25, 2021 at 05:22:02PM -0300, Tulio Magno Quites Machado Filho wrote:
> Adhemerval Zanella via Libc-alpha <libc-alpha@sourceware.org> writes:
>
> > On 21/01/2021 22:29, Tulio Magno Quites Machado Filho via Libc-alpha wrote:
>
> > So, what I recommend you to do is:
> >
> > 1. Change the documentation patch [1] and update the powerpc
> > sysdeps/powerpc/powerpc64/le/configure.ac to check 'as' version
> > instead of 'objcopy'.
>
> This has already been changed in the following patch:
> https://sourceware.org/pipermail/libc-alpha/2021-January/121919.html
>
> It's still missing the configure check, though. I'm working on that.
>
> > 2. Add a configure check for the new TLS using PC-relative and
> > set a new config.h flag (SUPPORT_PPC_TLS_PCREL).
>
> Ack. I'm working on it.
mod-tlsopt-powerpc.c and tls-macros.h are used only by the
testsuite, so don't fuss too much. Hopefully one day those files will
disappear.
@@ -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"
@@ -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