| Message ID | 1395766541-23979-12-git-send-email-julien.grall@linaro.org |
|---|---|
| State | Deferred, archived |
| Headers | show |
On Tue, 2014-03-25 at 16:55 +0000, Julien Grall wrote: > Clang doesn't support named register. Introduce __builtin_stack_pointer > to be able to use named register with gcc. I think gcc considers the __builtin namespace to be its own, not sure about clang. I think get_stack_pointer() would be a fine name for this macro. It seems like the clang version should work for both gcc and clang. Google seems to suggest that __builtin_stack_pointer might become a real compiler builtin at some point.
Hi Ian, On 03/25/2014 05:18 PM, Ian Campbell wrote: > On Tue, 2014-03-25 at 16:55 +0000, Julien Grall wrote: >> Clang doesn't support named register. Introduce __builtin_stack_pointer >> to be able to use named register with gcc. > > I think gcc considers the __builtin namespace to be its own, not sure > about clang. I'm able to compile on GCC without any issue. > I think get_stack_pointer() would be a fine name for this macro. It > seems like the clang version should work for both gcc and clang. > > Google seems to suggest that __builtin_stack_pointer might become a real > compiler builtin at some point. I took the idea to the llvmlinux project: http://git.linuxfoundation.org/?p=llvmlinux.git;a=blob;f=arch/arm/patches/current_stack_pointer_arm.patch; But I can rename into get_stack_pointer for the next version. Regards,
On Tue, 2014-03-25 at 18:01 +0000, Julien Grall wrote: > Hi Ian, > > On 03/25/2014 05:18 PM, Ian Campbell wrote: > > On Tue, 2014-03-25 at 16:55 +0000, Julien Grall wrote: > >> Clang doesn't support named register. Introduce __builtin_stack_pointer > >> to be able to use named register with gcc. > > > > I think gcc considers the __builtin namespace to be its own, not sure > > about clang. > > I'm able to compile on GCC without any issue. That's not the point. The point of a namespacing rule is that gcc can add such a function at any time it likes, and if that breaks your application then that is tough luck. > > I think get_stack_pointer() would be a fine name for this macro. It > > seems like the clang version should work for both gcc and clang. > > > > Google seems to suggest that __builtin_stack_pointer might become a real > > compiler builtin at some point. > > I took the idea to the llvmlinux project: > http://git.linuxfoundation.org/?p=llvmlinux.git;a=blob;f=arch/arm/patches/current_stack_pointer_arm.patch; > > But I can rename into get_stack_pointer for the next version. Sounds good, thanks. Ian.
On 26/03/14 10:31, Ian Campbell wrote: > On Tue, 2014-03-25 at 18:01 +0000, Julien Grall wrote: >> Hi Ian, >> >> On 03/25/2014 05:18 PM, Ian Campbell wrote: >>> On Tue, 2014-03-25 at 16:55 +0000, Julien Grall wrote: >>>> Clang doesn't support named register. Introduce __builtin_stack_pointer >>>> to be able to use named register with gcc. >>> >>> I think gcc considers the __builtin namespace to be its own, not sure >>> about clang. >> >> I'm able to compile on GCC without any issue. > > That's not the point. The point of a namespacing rule is that gcc can > add such a function at any time it likes, and if that breaks your > application then that is tough luck. Thanks, I didn't find anything useful on internet about namespace. It seems the common rule is __foo is reserved by the compiler. >>> I think get_stack_pointer() would be a fine name for this macro. It >>> seems like the clang version should work for both gcc and clang. >>> >>> Google seems to suggest that __builtin_stack_pointer might become a real >>> compiler builtin at some point. >> >> I took the idea to the llvmlinux project: >> http://git.linuxfoundation.org/?p=llvmlinux.git;a=blob;f=arch/arm/patches/current_stack_pointer_arm.patch; >> >> But I can rename into get_stack_pointer for the next version. > > Sounds good, thanks. I will rename it and send the pathc. Regards,
On Wed, 2014-03-26 at 10:38 +0000, Julien Grall wrote: > > On 26/03/14 10:31, Ian Campbell wrote: > > On Tue, 2014-03-25 at 18:01 +0000, Julien Grall wrote: > >> Hi Ian, > >> > >> On 03/25/2014 05:18 PM, Ian Campbell wrote: > >>> On Tue, 2014-03-25 at 16:55 +0000, Julien Grall wrote: > >>>> Clang doesn't support named register. Introduce __builtin_stack_pointer > >>>> to be able to use named register with gcc. > >>> > >>> I think gcc considers the __builtin namespace to be its own, not sure > >>> about clang. > >> > >> I'm able to compile on GCC without any issue. > > > > That's not the point. The point of a namespacing rule is that gcc can > > add such a function at any time it likes, and if that breaks your > > application then that is tough luck. > > Thanks, I didn't find anything useful on internet about namespace. It > seems the common rule is __foo is reserved by the compiler. Yes, I think that comes from the C standard. odd numbers of _ are for the libc (by POSIX I think) and even numbers for the compiler (by the C std).
diff --git a/xen/include/asm-arm/current.h b/xen/include/asm-arm/current.h index 65c0cdf..0d4a8c0 100644 --- a/xen/include/asm-arm/current.h +++ b/xen/include/asm-arm/current.h @@ -25,10 +25,23 @@ struct cpu_info { unsigned int pad; }; +#ifdef __clang__ +#define __builtin_stack_pointer() ({ \ + unsigned long current_sp; \ + asm ("mov %0, sp" : "=r" (current_sp)); \ + current_sp; \ +}) +#else +#define __builtin_stack_pointer() ({ \ + register unsigned long current_sp asm ("sp"); \ + current_sp; \ +}) +#endif + static inline struct cpu_info *get_cpu_info(void) { - register unsigned long sp asm ("sp"); - return (struct cpu_info *)((sp & ~(STACK_SIZE - 1)) + STACK_SIZE - sizeof(struct cpu_info)); + return (struct cpu_info *)((__builtin_stack_pointer() & ~(STACK_SIZE - 1)) + + STACK_SIZE - sizeof(struct cpu_info)); } #define guest_cpu_user_regs() (&get_cpu_info()->guest_cpu_user_regs)
Clang doesn't support named register. Introduce __builtin_stack_pointer to be able to use named register with gcc. In file included from arm32/asm-offsets.c:10: In file included from xen/xen/include/xen/sched.h:18: In file included from xen/xen/include/xen/smp.h:4: In file included from xen/xen/include/asm/smp.h:8: xen/xen/include/asm/current.h:31:33: error: variable 'sp' is uninitialized when used here [-Werror,-Wuninitialized] return (struct cpu_info *)((sp & ~(STACK_SIZE - 1)) + STACK_SIZE - sizeof(struct cpu_info)); ^~ xen/xen/include/asm/current.h:30:30: note: initialize the variable 'sp' to silence this warning register unsigned long sp asm ("sp"); ^ = 0 Signed-off-by: Julien Grall <julien.grall@linaro.org> Cc: Ian Campbell <ian.campbell@citrix.com> Cc: Stefano Stabellini <stefano.stabellini@citrix.com> Cc: Tim Deegan <tim@xen.org> --- xen/include/asm-arm/current.h | 17 +++++++++++++++-- 1 file changed, 15 insertions(+), 2 deletions(-)