From: Andreas Schwab <schwab@linux-m68k.org>
To: "H.J. Lu" <hjl.tools@gmail.com>
Cc: "Carlos O'Donell via Libc-alpha" <libc-alpha@sourceware.org>,
"Carlos O'Donell" <carlos@redhat.com>
Subject: Re: [PATCH v5] x86_64: Update THREAD_SETMEM/THREAD_SETMEM_NC for IMM64 [BZ #27591]
Date: Tue, 16 Mar 2021 17:02:36 +0100 [thread overview]
Message-ID: <87zgz3xf1f.fsf@igel.home> (raw)
In-Reply-To: <CAMe9rOpFyz495-B_VrvNAMENLGSPiSbLFZk6cO_0deB3ei373w@mail.gmail.com> (H. J. Lu's message of "Tue, 16 Mar 2021 08:45:25 -0700")
On Mär 16 2021, H.J. Lu wrote:
> diff --git a/sysdeps/x86_64/nptl/tls.h b/sysdeps/x86_64/nptl/tls.h
> index 20f0958780..b19d90433d 100644
> --- a/sysdeps/x86_64/nptl/tls.h
> +++ b/sysdeps/x86_64/nptl/tls.h
> @@ -271,9 +271,18 @@ _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))); \
> + /* Since movq takes a register or a signed 32-bit immediate source \
> + operand, select the immediate source operand only if it is known \
> + to be 32-bit signed immediate at compile-time. */ \
> + if (__builtin_constant_p (value) \
> + && (int64_t) (int32_t) (uintptr_t) value == (uintptr_t) value) \
> + asm volatile ("movq %0,%%fs:%P1" : \
> + : "i" ((uint64_t) cast_to_integer (value)), \
> + "i" (offsetof (struct pthread, member))); \
> + else \
> + asm volatile ("movq %q0,%%fs:%P1" : \
> + : "r" ((uint64_t) cast_to_integer (value)), \
> + "i" (offsetof (struct pthread, member))); \
I don't think this will work in general. Wouldn't it be possible that
an operands optimizes to a 64-bit constant in later passes? What you
really need is a constraint that only matches a 32-bit immediate or a
register. Like "rWf"?
Andreas.
--
Andreas Schwab, schwab@linux-m68k.org
GPG Key fingerprint = 7578 EB47 D4E5 4D69 2510 2552 DF73 E780 A9DA AEC1
"And now for something completely different."
next prev parent reply other threads:[~2021-03-16 16:02 UTC|newest]
Thread overview: 15+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-02-02 19:12 [PATCH] x86_64: Update THREAD_SETMEM/THREAD_SETMEM_NC for IMM64 H.J. Lu
2021-03-01 13:30 ` Carlos O'Donell
2021-03-02 14:21 ` [PATCH v2] " H.J. Lu
2021-03-08 22:28 ` 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 [this message]
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
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