| Message ID | 20241105023406.1415969-2-caiyinyu@loongson.cn |
|---|---|
| State | New |
| Headers | show |
| Series | nptl: fix __builtin_thread_pointer detection on LoongArch | expand |
On Tue, 2024-11-05 at 10:34 +0800, caiyinyu wrote: > this is version 3 disscussed in https://sourceware.org/pipermail/libc-alpha/2024-November/161236.html > v2: https://sourceware.org/pipermail/libc-alpha/2024-November/161213.html > v1: https://sourceware.org/pipermail/libc-alpha/2024-November/161185.html Technically, 'register void *tp asm("tp");' may produce better code than using asm("move %0, tp"). The reason is in the latter the compiler does not know we are just doing a move (as it does not parse assembly). For example register void *_tp asm("tp"); void *tp() { return _tp; } int tp_rel_load() { return *((int*)tp() + 384); } gives: ldptr.w $r4,$r2,1536 But if we use asm("move ...") for tp(), we'll get: #APP # 5 "t.c" 1 move $r12, $tp # 0 "" 2 #NO_APP ldptr.w $r4,$r12,1536 jr $r1 i.e. we'll be wasting one insn with asm("move ..."). Thus IMO a better approach would be moving __thread_self into thread_pointer.h, and including thread_pointer.h from tls.h? Like: diff --git a/sysdeps/loongarch/nptl/thread_pointer.h b/sysdeps/loongarch/nptl/thread_pointer.h index 5dec2ef4c6..930c73606c 100644 --- a/sysdeps/loongarch/nptl/thread_pointer.h +++ b/sysdeps/loongarch/nptl/thread_pointer.h @@ -21,16 +21,12 @@ #include <sys/cdefs.h> +register void *__thread_self asm("tp"); + static inline void * __thread_pointer (void) { -#if __glibc_has_builtin (__builtin_thread_pointer) - return __builtin_thread_pointer (); -#else - void *__thread_register; - __asm__ ("move %0, $tp" : "=r" (__thread_register)); - return __thread_register; -#endif + return __thread_self; } #endif /* _SYS_THREAD_POINTER_H */ diff --git a/sysdeps/loongarch/nptl/tls.h b/sysdeps/loongarch/nptl/tls.h index ac1a92ea7b..675c0d27c1 100644 --- a/sysdeps/loongarch/nptl/tls.h +++ b/sysdeps/loongarch/nptl/tls.h @@ -26,8 +26,8 @@ #include <stddef.h> #include <stdint.h> #include <dl-dtv.h> +#include "thread_pointer.h" -register void *__thread_self asm ("$tp"); #define READ_THREAD_POINTER() ({ __thread_self; }) /* Get system call information. */ ? > --- > sysdeps/loongarch/nptl/thread_pointer.h | 6 ------ > 1 file changed, 6 deletions(-) > > diff --git a/sysdeps/loongarch/nptl/thread_pointer.h b/sysdeps/loongarch/nptl/thread_pointer.h > index 5dec2ef4c6..3c5367af24 100644 > --- a/sysdeps/loongarch/nptl/thread_pointer.h > +++ b/sysdeps/loongarch/nptl/thread_pointer.h > @@ -19,18 +19,12 @@ > #ifndef _SYS_THREAD_POINTER_H > #define _SYS_THREAD_POINTER_H > > -#include <sys/cdefs.h> > - > static inline void * > __thread_pointer (void) > { > -#if __glibc_has_builtin (__builtin_thread_pointer) > - return __builtin_thread_pointer (); > -#else > void *__thread_register; > __asm__ ("move %0, $tp" : "=r" (__thread_register)); > return __thread_register; > -#endif > } > > #endif /* _SYS_THREAD_POINTER_H */
diff --git a/sysdeps/loongarch/nptl/thread_pointer.h b/sysdeps/loongarch/nptl/thread_pointer.h index 5dec2ef4c6..3c5367af24 100644 --- a/sysdeps/loongarch/nptl/thread_pointer.h +++ b/sysdeps/loongarch/nptl/thread_pointer.h @@ -19,18 +19,12 @@ #ifndef _SYS_THREAD_POINTER_H #define _SYS_THREAD_POINTER_H -#include <sys/cdefs.h> - static inline void * __thread_pointer (void) { -#if __glibc_has_builtin (__builtin_thread_pointer) - return __builtin_thread_pointer (); -#else void *__thread_register; __asm__ ("move %0, $tp" : "=r" (__thread_register)); return __thread_register; -#endif } #endif /* _SYS_THREAD_POINTER_H */