This is the mail archive of the libc-alpha@sourceware.org mailing list for the glibc project.

Index Nav:	[Date Index] [Subject Index] [Author Index] [Thread Index]
Message Nav:	[Date Prev] [Date Next]	[Thread Prev] [Thread Next]
Other format:	[Raw text]

Re: [PATCH] x86-64: Use direct TLS initial-exec access to update errno

From: Florian Weimer <fweimer at redhat dot com>
To: "H.J. Lu" <hjl dot tools at gmail dot com>, GNU C Library <libc-alpha at sourceware dot org>
Date: Tue, 5 Dec 2017 14:47:21 +0100
Subject: Re: [PATCH] x86-64: Use direct TLS initial-exec access to update errno
Authentication-results: sourceware.org; auth=none
References: <20171204231315.GA17402@intel.com>

On 12/05/2017 12:13 AM, H.J. Lu wrote:

-	/* Align stack to 16 bytes.  */
-	subq	$8, %rsp
-	cfi_adjust_cfa_offset (8)
-	/* Here if x is Inf. Set errno to EDOM.  */
-	call	JUMPTARGET(__errno_location)
-	addq	$8, %rsp
-	cfi_adjust_cfa_offset (-8)
-
-	movl	$EDOM, (%rax)
+	movq	errno@gottpoff(%rip), %rax
+	movl	$EDOM, %fs:(%rax)

If you replace subq/addq with push/pop of a dummy register, then, the__errno_location approach results in more compact code, I think.


Thanks,
Florian

References:
- [PATCH] x86-64: Use direct TLS initial-exec access to update errno
  - From: H.J. Lu

Index Nav:	[Date Index] [Subject Index] [Author Index] [Thread Index]
Message Nav:	[Date Prev] [Date Next]	[Thread Prev] [Thread Next]