From: Stefano Stabellini <sstabellini@kernel.org>
To: Julien Grall <julien.grall@arm.com>
Cc: Artem_Mygaiev@epam.com, xen-devel@lists.xenproject.org,
sstabellini@kernel.org, Andrii_Anisov@epam.com,
Oleksandr_Tyshchenko@epam.com
Subject: Re: [PATCH 02/12] xen/arm: fix get_cpu_info() when built with clang
Date: Wed, 17 Apr 2019 13:45:18 -0700 (PDT) [thread overview]
Message-ID: <alpine.DEB.2.10.1904171340390.1370@sstabellini-ThinkPad-X260> (raw)
In-Reply-To: <20190327184531.30986-3-julien.grall@arm.com>
On Wed, 27 Mar 2019, Julien Grall wrote:
> Clang understands the GCCism in use here, but still complains that sp is
> unitialised. In such cases, resort to the older versions of this code,
> which directly read sp into the temporary variable.
>
> Note that we still keep the GCCism in the default case, as it causes GCC
> to create rather better assembly.
>
> This is based on the x86 counterpart.
I understand this is based on an existing approach but what about other
compilers? I have a suggestion below.
> Signed-off-by: Julien Grall <julien.grall@arm.com>
> ---
> xen/include/asm-arm/current.h | 10 +++++++++-
> 1 file changed, 9 insertions(+), 1 deletion(-)
>
> diff --git a/xen/include/asm-arm/current.h b/xen/include/asm-arm/current.h
> index c4af66fbb9..6b7c1df64d 100644
> --- a/xen/include/asm-arm/current.h
> +++ b/xen/include/asm-arm/current.h
> @@ -28,8 +28,16 @@ struct cpu_info {
>
> static inline struct cpu_info *get_cpu_info(void)
> {
> +#ifdef __clang__
> + unsigned long sp;
> +
> + asm ("mov %0, sp" : "=r" (sp));
> +#else
> register unsigned long sp asm ("sp");
> - return (struct cpu_info *)((sp & ~(STACK_SIZE - 1)) + STACK_SIZE - sizeof(struct cpu_info));
> +#endif
> +
> + return (struct cpu_info *)((sp & ~(STACK_SIZE - 1)) +
> + STACK_SIZE - sizeof(struct cpu_info));
> }
I think it makes sense to switch the #ifdef around:
#ifdef __GNUC__
/* gcc specific optimization */
#else
/* regular implementation */
#endif
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WARNING: multiple messages have this Message-ID (diff)
From: Stefano Stabellini <sstabellini@kernel.org>
To: Julien Grall <julien.grall@arm.com>
Cc: Artem_Mygaiev@epam.com, xen-devel@lists.xenproject.org,
sstabellini@kernel.org, Andrii_Anisov@epam.com,
Oleksandr_Tyshchenko@epam.com
Subject: Re: [Xen-devel] [PATCH 02/12] xen/arm: fix get_cpu_info() when built with clang
Date: Wed, 17 Apr 2019 13:45:18 -0700 (PDT) [thread overview]
Message-ID: <alpine.DEB.2.10.1904171340390.1370@sstabellini-ThinkPad-X260> (raw)
Message-ID: <20190417204518.FIf6jfiBvT86VFzpoyXa5jxFUfqKNE59zpDFA47J3U4@z> (raw)
In-Reply-To: <20190327184531.30986-3-julien.grall@arm.com>
On Wed, 27 Mar 2019, Julien Grall wrote:
> Clang understands the GCCism in use here, but still complains that sp is
> unitialised. In such cases, resort to the older versions of this code,
> which directly read sp into the temporary variable.
>
> Note that we still keep the GCCism in the default case, as it causes GCC
> to create rather better assembly.
>
> This is based on the x86 counterpart.
I understand this is based on an existing approach but what about other
compilers? I have a suggestion below.
> Signed-off-by: Julien Grall <julien.grall@arm.com>
> ---
> xen/include/asm-arm/current.h | 10 +++++++++-
> 1 file changed, 9 insertions(+), 1 deletion(-)
>
> diff --git a/xen/include/asm-arm/current.h b/xen/include/asm-arm/current.h
> index c4af66fbb9..6b7c1df64d 100644
> --- a/xen/include/asm-arm/current.h
> +++ b/xen/include/asm-arm/current.h
> @@ -28,8 +28,16 @@ struct cpu_info {
>
> static inline struct cpu_info *get_cpu_info(void)
> {
> +#ifdef __clang__
> + unsigned long sp;
> +
> + asm ("mov %0, sp" : "=r" (sp));
> +#else
> register unsigned long sp asm ("sp");
> - return (struct cpu_info *)((sp & ~(STACK_SIZE - 1)) + STACK_SIZE - sizeof(struct cpu_info));
> +#endif
> +
> + return (struct cpu_info *)((sp & ~(STACK_SIZE - 1)) +
> + STACK_SIZE - sizeof(struct cpu_info));
> }
I think it makes sense to switch the #ifdef around:
#ifdef __GNUC__
/* gcc specific optimization */
#else
/* regular implementation */
#endif
_______________________________________________
Xen-devel mailing list
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next prev parent reply other threads:[~2019-04-17 20:45 UTC|newest]
Thread overview: 104+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-03-27 18:45 [PATCH 00/12] xen/arm: Add support to build with clang Julien Grall
2019-03-27 18:45 ` [PATCH 01/12] xen: clang: Support correctly cross-compile Julien Grall
2019-03-28 9:55 ` Jan Beulich
2019-03-28 10:14 ` Andrew Cooper
2019-03-28 10:28 ` Jan Beulich
2019-03-28 10:43 ` Andrew Cooper
2019-03-28 10:56 ` Jan Beulich
2019-03-29 10:09 ` Julien Grall
2019-03-29 9:41 ` Julien Grall
2019-03-29 10:14 ` Jan Beulich
2019-04-19 18:47 ` Stefano Stabellini
2019-04-19 18:47 ` [Xen-devel] " Stefano Stabellini
2019-04-24 20:18 ` Julien Grall
2019-04-24 20:18 ` [Xen-devel] " Julien Grall
2019-03-27 18:45 ` [PATCH 02/12] xen/arm: fix get_cpu_info() when built with clang Julien Grall
2019-04-17 20:45 ` Stefano Stabellini [this message]
2019-04-17 20:45 ` [Xen-devel] " Stefano Stabellini
2019-04-17 21:00 ` Julien Grall
2019-04-17 21:00 ` [Xen-devel] " Julien Grall
2019-04-18 18:03 ` Stefano Stabellini
2019-04-18 18:03 ` [Xen-devel] " Stefano Stabellini
2019-09-29 14:26 ` Julien Grall
2019-10-01 1:15 ` Stefano Stabellini
2019-10-01 1:22 ` Stefano Stabellini
2019-10-01 9:49 ` Julien Grall
2019-10-01 9:47 ` Julien Grall
2019-03-27 18:45 ` [PATCH 03/12] xen/arm: zynqmp: Fix header guard for xilinx-zynqmp-eemi.h Julien Grall
2019-04-17 20:20 ` Stefano Stabellini
2019-04-17 20:20 ` [Xen-devel] " Stefano Stabellini
2019-03-27 18:45 ` [PATCH 04/12] xen/arm: memaccess: Initialize correctly *access in __p2m_get_mem_access Julien Grall
2019-03-27 19:08 ` Razvan Cojocaru
2019-03-27 18:45 ` [PATCH 05/12] xen/arm64: bitops: Match the register size with the value size in flsl Julien Grall
2019-03-27 19:03 ` Andrew Cooper
2019-03-27 20:13 ` Julien Grall
2019-04-17 20:24 ` Stefano Stabellini
2019-04-17 20:24 ` [Xen-devel] " Stefano Stabellini
2019-04-17 21:02 ` Julien Grall
2019-04-17 21:02 ` [Xen-devel] " Julien Grall
2019-04-18 18:40 ` Stefano Stabellini
2019-04-18 18:40 ` [Xen-devel] " Stefano Stabellini
2019-04-18 18:57 ` Julien Grall
2019-04-18 18:57 ` [Xen-devel] " Julien Grall
2019-04-18 19:00 ` Stefano Stabellini
2019-04-18 19:00 ` [Xen-devel] " Stefano Stabellini
2019-03-27 18:45 ` [PATCH 06/12] xen/arm64: sysreg: Implement the 32-bit helpers using the 64-bit helpers Julien Grall
2019-03-27 19:15 ` Andrew Cooper
2019-03-27 20:21 ` Julien Grall
2019-04-17 20:26 ` Stefano Stabellini
2019-04-17 20:26 ` [Xen-devel] " Stefano Stabellini
2019-03-27 18:45 ` [PATCH 07/12] xen/arm: cpuerrata: Match register size with value size in check_workaround_* Julien Grall
2019-04-17 20:28 ` Stefano Stabellini
2019-04-17 20:28 ` [Xen-devel] " Stefano Stabellini
2019-04-17 21:15 ` Julien Grall
2019-04-17 21:15 ` [Xen-devel] " Julien Grall
2019-04-18 18:23 ` Stefano Stabellini
2019-04-18 18:23 ` [Xen-devel] " Stefano Stabellini
2019-04-18 18:47 ` Julien Grall
2019-04-18 18:47 ` [Xen-devel] " Julien Grall
2019-04-18 18:52 ` Stefano Stabellini
2019-04-18 18:52 ` [Xen-devel] " Stefano Stabellini
2019-04-18 19:01 ` Julien Grall
2019-04-18 19:01 ` [Xen-devel] " Julien Grall
2019-04-18 19:04 ` Stefano Stabellini
2019-04-18 19:04 ` [Xen-devel] " Stefano Stabellini
2019-03-27 18:45 ` [PATCH 08/12] xen/arm: cpufeature: Match register size with value size in cpus_have_const_cap Julien Grall
2019-04-17 20:29 ` Stefano Stabellini
2019-04-17 20:29 ` [Xen-devel] " Stefano Stabellini
2019-04-17 21:16 ` Julien Grall
2019-04-17 21:16 ` [Xen-devel] " Julien Grall
2019-03-27 18:45 ` [PATCH 09/12] xen/arm: guest_walk: Avoid theoritical unitialized value in get_top_bit Julien Grall
2019-04-17 20:31 ` Stefano Stabellini
2019-04-17 20:31 ` [Xen-devel] " Stefano Stabellini
2019-03-27 18:45 ` [PATCH 10/12] xen/arm: mm: Mark check_memory_layout_alignment_constraints as unused Julien Grall
2019-03-27 19:10 ` Andrew Cooper
2019-04-09 12:09 ` Julien Grall
2019-04-09 12:09 ` [Xen-devel] " Julien Grall
2019-03-27 18:45 ` [PATCH 11/12] xen/arm: traps: Mark check_stack_alignment_constraints " Julien Grall
2019-03-27 18:45 ` [PATCH 12/12] xen/arm64: __cmpxchg and __cmpxchg_mb should always be inline Julien Grall
2019-04-17 20:35 ` Stefano Stabellini
2019-04-17 20:35 ` [Xen-devel] " Stefano Stabellini
2019-03-28 11:27 ` [PATCH 00/12] xen/arm: Add support to build with clang Artem Mygaiev
2019-03-29 10:13 ` Julien Grall
2019-04-16 22:43 ` Stefano Stabellini
2019-04-16 22:43 ` [Xen-devel] " Stefano Stabellini
2019-04-17 9:42 ` Julien Grall
2019-04-17 9:42 ` [Xen-devel] " Julien Grall
2019-04-18 9:15 ` Artem Mygaiev
2019-04-18 9:15 ` [Xen-devel] " Artem Mygaiev
2019-04-18 10:43 ` Julien Grall
2019-04-18 10:43 ` [Xen-devel] " Julien Grall
2019-04-18 11:15 ` Artem Mygaiev
2019-04-18 11:15 ` [Xen-devel] " Artem Mygaiev
2019-04-18 18:33 ` Julien Grall
2019-04-18 18:33 ` [Xen-devel] " Julien Grall
2019-04-23 13:39 ` Artem Mygaiev
2019-04-23 13:39 ` [Xen-devel] " Artem Mygaiev
2019-04-24 21:07 ` Julien Grall
2019-04-24 21:07 ` [Xen-devel] " Julien Grall
2019-04-25 3:31 ` Artem Mygaiev
2019-04-25 3:31 ` [Xen-devel] " Artem Mygaiev
2019-04-24 11:01 ` Roger Pau Monné
2019-04-24 11:01 ` [Xen-devel] " Roger Pau Monné
2019-04-18 11:13 ` Julien Grall
2019-04-18 11:13 ` [Xen-devel] " Julien Grall
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