From: "H.J. Lu" <hjl.tools@gmail.com>
To: "Carlos O'Donell" <carlos@redhat.com>
Cc: GNU C Library <libc-alpha@sourceware.org>
Subject: [PATCH v2] x86_64: Update THREAD_SETMEM/THREAD_SETMEM_NC for IMM64
Date: Tue, 2 Mar 2021 06:21:00 -0800 [thread overview]
Message-ID: <CAMe9rOoYT36HpmoBz9NpnOsK+Q_-T8v7TQpdBBNzwvvTnCCuEg@mail.gmail.com> (raw)
In-Reply-To: <a077ae86-ebcd-0838-1a6c-e36ec9dbd78f@redhat.com>
[-- Attachment #1: Type: text/plain, Size: 5230 bytes --]
On Mon, Mar 1, 2021 at 5:30 AM Carlos O'Donell <carlos@redhat.com> wrote:
>
> On 2/2/21 2:12 PM, H.J. Lu via Libc-alpha wrote:
> > Since there is only "movq imm32s, mem64" and no "movq imm64, mem64", use
> > "movq reg64, mem64" to store 64-bit constant in TCB.
> > ---
> > sysdeps/x86_64/nptl/tls.h | 11 +++++++++++
> > 1 file changed, 11 insertions(+)
> >
> > diff --git a/sysdeps/x86_64/nptl/tls.h b/sysdeps/x86_64/nptl/tls.h
> > index 20f0958780..9ec8703e45 100644
> > --- a/sysdeps/x86_64/nptl/tls.h
> > +++ b/sysdeps/x86_64/nptl/tls.h
> > @@ -269,6 +269,11 @@ _Static_assert (offsetof (tcbhead_t, __glibc_unused2) == 0x80,
> > asm volatile ("movl %0,%%fs:%P1" : \
> > : IMM_MODE (value), \
> > "i" (offsetof (struct pthread, member))); \
> > + else if (__builtin_constant_p (value) \
> > + && (int64_t) (int32_t) (uintptr_t) value != (uintptr_t) value) \
> > + asm volatile ("movq %0,%%fs:%P1" : \
> > + : "r" (value), \
> > + "i" (offsetof (struct pthread, member))); \
>
> (1) Move conditional into 'else /* 8 */' section.
>
> The blocks of conditionals are predicated on the size of the member we are
> about to write to.
>
> In the block below...
>
> > else /* 8 */ \
>
> ... here, we are about to write value into a member that is size 8.
>
> Your code changes the logical construction of the code, but in way that makes
> it more difficult to understand.
>
> We previously had:
>
> if (sizeof() == 1)
>
> else if (sizeof() == 4)
>
> else /* Assume 8 */
>
> In your case we must already be in the 'else /* Assume 8 */' because otherwise
> we've be writing a 64-bit constant into a < 64-bit structure member.
>
> I think we should put your code into the else clause.
>
> 272 else /* 8 */ \
> 273 { \
>
> if (__builtin_constant_p (value)
> && ([the value is a >32-bit constant])
> asm volatile ([use movq reg64, mem64]);
> else
>
> 274 asm volatile ("movq %q0,%%fs:%P1" : \
> 275 : IMM_MODE ((uint64_t) cast_to_integer (value)), \
> 276 "i" (offsetof (struct pthread, member))); \
> 277 }})
>
> (2) What if gcc can't prove it's constant?
>
> If the constant is >32-bit, but gcc can't prove it's constant, then don't we
> try to put a >32-bit constant into a 32-bit immediate?
>
> Shouldn't the code be structured the other way around?
>
> e.g.
>
> else /* 8 */
> {
> if (__builtin_constant_p (value)
> && ([the value is a <= 32-bit constant])
> asm volatile ([use movq imm32, mem64]);
> else
> asm volatile ([use movq reg64, mem64]);
> }
>
> This way the code is always correct?
I changed it to
if (!__builtin_constant_p (value) \
|| (int64_t) (int32_t) (uintptr_t) value == (uintptr_t) value) \
asm volatile ("movq %q0,%%fs:%P1" : \
: IMM_MODE ((uint64_t) cast_to_integer (value)), \
"i" (offsetof (struct pthread, member))); \
else \
asm volatile ("movq %0,%%fs:%P1" : \
: "r" (value), \
"i" (offsetof (struct pthread, member))); \
> > { \
> > asm volatile ("movq %q0,%%fs:%P1" : \
> > @@ -294,6 +299,12 @@ _Static_assert (offsetof (tcbhead_t, __glibc_unused2) == 0x80,
> > : IMM_MODE (value), \
> > "i" (offsetof (struct pthread, member[0])), \
> > "r" (idx)); \
> > + else if (__builtin_constant_p (value) \
> > + && (int64_t) (int32_t) (uintptr_t) value != (uintptr_t) value) \
> > + asm volatile ("movq %0,%%fs:%P1(,%q2,8)" : \
> > + : "r" (value), \
> > + "i" (offsetof (struct pthread, member[0])), \
> > + "r" (idx)); \
> > else /* 8 */ \
> > { \
> > asm volatile ("movq %q0,%%fs:%P1(,%q2,8)" : \
> >
>
Here is the v2 patch. OK for master?
Thanks.
--
H.J.
[-- Attachment #2: v2-0001-x86_64-Update-THREAD_SETMEM-THREAD_SETMEM_NC-for-.patch --]
[-- Type: text/x-patch, Size: 2417 bytes --]
From 4fbc9ab67933d662506a01658d4c81a922e50fdf Mon Sep 17 00:00:00 2001
From: "H.J. Lu" <hjl.tools@gmail.com>
Date: Fri, 8 Jan 2021 15:38:14 -0800
Subject: [PATCH v2] x86_64: Update THREAD_SETMEM/THREAD_SETMEM_NC for IMM64
Since there is only "movq imm32s, mem64" and no "movq imm64, mem64", use
"movq reg64, mem64" to store 64-bit constant.
---
sysdeps/x86_64/nptl/tls.h | 27 ++++++++++++++++++++-------
1 file changed, 20 insertions(+), 7 deletions(-)
diff --git a/sysdeps/x86_64/nptl/tls.h b/sysdeps/x86_64/nptl/tls.h
index 20f0958780..0dbd66209c 100644
--- a/sysdeps/x86_64/nptl/tls.h
+++ b/sysdeps/x86_64/nptl/tls.h
@@ -271,9 +271,15 @@ _Static_assert (offsetof (tcbhead_t, __glibc_unused2) == 0x80,
"i" (offsetof (struct pthread, member))); \
else /* 8 */ \
{ \
- asm volatile ("movq %q0,%%fs:%P1" : \
- : IMM_MODE ((uint64_t) cast_to_integer (value)), \
- "i" (offsetof (struct pthread, member))); \
+ if (!__builtin_constant_p (value) \
+ || (int64_t) (int32_t) (uintptr_t) value == (uintptr_t) value) \
+ asm volatile ("movq %q0,%%fs:%P1" : \
+ : IMM_MODE ((uint64_t) cast_to_integer (value)), \
+ "i" (offsetof (struct pthread, member))); \
+ else \
+ asm volatile ("movq %0,%%fs:%P1" : \
+ : "r" (value), \
+ "i" (offsetof (struct pthread, member))); \
}})
@@ -296,10 +302,17 @@ _Static_assert (offsetof (tcbhead_t, __glibc_unused2) == 0x80,
"r" (idx)); \
else /* 8 */ \
{ \
- asm volatile ("movq %q0,%%fs:%P1(,%q2,8)" : \
- : IMM_MODE ((uint64_t) cast_to_integer (value)), \
- "i" (offsetof (struct pthread, member[0])), \
- "r" (idx)); \
+ if (!__builtin_constant_p (value) \
+ || (int64_t) (int32_t) (uintptr_t) value == (uintptr_t) value) \
+ asm volatile ("movq %q0,%%fs:%P1(,%q2,8)" : \
+ : IMM_MODE ((uint64_t) cast_to_integer (value)), \
+ "i" (offsetof (struct pthread, member[0])), \
+ "r" (idx)); \
+ else \
+ asm volatile ("movq %0,%%fs:%P1(,%q2,8)" : \
+ : "r" (value), \
+ "i" (offsetof (struct pthread, member[0])), \
+ "r" (idx)); \
}})
--
2.29.2
next prev parent reply other threads:[~2021-03-02 14:21 UTC|newest]
Thread overview: 15+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-02-02 19:12 [PATCH] " H.J. Lu
2021-03-01 13:30 ` Carlos O'Donell
2021-03-02 14:21 ` H.J. Lu [this message]
2021-03-08 22:28 ` [PATCH v2] " Carlos O'Donell
2021-03-09 0:09 ` [PATCH v3] " H.J. Lu
2021-03-15 12:49 ` Carlos O'Donell
2021-03-15 13:29 ` [PATCH v4] " H.J. Lu
2021-03-16 3:01 ` Carlos O'Donell
2021-03-16 9:04 ` Andreas Schwab
2021-03-16 15:45 ` [PATCH v5] x86_64: Update THREAD_SETMEM/THREAD_SETMEM_NC for IMM64 [BZ #27591] H.J. Lu
2021-03-16 16:02 ` Andreas Schwab
2021-03-16 16:10 ` Florian Weimer
2021-03-16 16:34 ` Carlos O'Donell
2021-03-16 16:50 ` [PATCH v6] x86_64: Correct THREAD_SETMEM/THREAD_SETMEM_NC for movq " H.J. Lu
2021-03-16 16:52 ` H.J. Lu
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=CAMe9rOoYT36HpmoBz9NpnOsK+Q_-T8v7TQpdBBNzwvvTnCCuEg@mail.gmail.com \
--to=hjl.tools@gmail.com \
--cc=carlos@redhat.com \
--cc=libc-alpha@sourceware.org \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for read-only IMAP folder(s) and NNTP newsgroup(s).