From: David Laight <[email protected]>
To: 'Ammar Faizi' <[email protected]>
Cc: "Willy Tarreau" <[email protected]>,
"Thomas Weißschuh" <[email protected]>,
"Nicholas Rosenberg" <[email protected]>,
"Alviro Iskandar Setiawan" <[email protected]>,
"Michael William Jonathan" <[email protected]>,
"GNU/Weeb Mailing List" <[email protected]>,
"Linux Kernel Mailing List" <[email protected]>
Subject: RE: [RFC PATCH v1 0/5] nolibc x86-64 string functions
Date: Fri, 1 Sep 2023 14:54:56 +0000 [thread overview]
Message-ID: <[email protected]> (raw)
In-Reply-To: <ZPH4I2W+zvhK93U/@biznet-home.integral.gnuweeb.org>
From: Ammar Faizi
> Sent: 01 September 2023 15:42
...
> > > " movq %rdx, %rcx\n"
> > > " movq %rdi, %rdx\n"
> > > " movq %rdi, %rax\n"
> >
> > You seem to have confused yourself about whether you are using %eax or %edx.
>
> What do you mean? They're all 64-bit pointers.
%ax, %eax, %rax - what is the difference :-)
> What I know is that the %rdx will be clobbered by "subq %rsi, %rdx"
> below and the %rax should be return value. That's why I copy the %rdi
> twice. memmove() returns the dst pointer. Did I miss something?
I'd forgotten about the (stupid) return value.
I'm pretty sure it is an accident from the original pdp-11
implementation from the days before C had an explicit 'return'
statement.
(The pdp-11 I used ran RSX/11M - so had a Fortran compiler
not a C one.)
David
-
Registered Address Lakeside, Bramley Road, Mount Farm, Milton Keynes, MK1 1PT, UK
Registration No: 1397386 (Wales)
next prev parent reply other threads:[~2023-09-01 14:55 UTC|newest]
Thread overview: 29+ messages / expand[flat|nested] mbox.gz Atom feed top
2023-08-30 13:57 [RFC PATCH v1 0/5] nolibc x86-64 string functions Ammar Faizi
2023-08-30 13:57 ` [RFC PATCH v1 1/5] tools/nolibc: x86-64: Use `rep movsb` for `memcpy()` and `memmove()` Ammar Faizi
2023-08-30 13:57 ` [RFC PATCH v1 2/5] tools/nolibc: x86-64: Use `rep stosb` for `memset()` Ammar Faizi
2023-08-30 14:08 ` Alviro Iskandar Setiawan
2023-08-30 14:13 ` Ammar Faizi
2023-08-30 14:24 ` Alviro Iskandar Setiawan
2023-08-30 15:09 ` Ammar Faizi
2023-08-30 15:23 ` Willy Tarreau
2023-08-30 15:44 ` Ammar Faizi
2023-08-30 15:51 ` Willy Tarreau
2023-08-30 16:08 ` Ammar Faizi
2023-08-30 16:11 ` Alviro Iskandar Setiawan
2023-08-30 13:57 ` [RFC PATCH v1 3/5] tools/nolibc: x86-64: Use `rep cmpsb` for `memcmp()` Ammar Faizi
2023-08-30 21:26 ` Willy Tarreau
2023-09-01 3:24 ` Ammar Faizi
2023-09-01 3:35 ` Willy Tarreau
2023-09-01 7:27 ` Ammar Faizi
2023-09-04 8:26 ` David Laight
2023-08-30 13:57 ` [RFC PATCH v1 4/5] tools/nolibc: string: Remove the `_nolibc_memcpy_down()` function Ammar Faizi
2023-08-30 21:27 ` Willy Tarreau
2023-08-30 13:57 ` [RFC PATCH v1 5/5] tools/nolibc: string: Remove the `_nolibc_memcpy_up()` function Ammar Faizi
2023-08-30 21:32 ` [RFC PATCH v1 0/5] nolibc x86-64 string functions Willy Tarreau
2023-09-01 11:34 ` David Laight
2023-09-01 11:46 ` Willy Tarreau
2023-09-01 13:06 ` Ammar Faizi
2023-09-01 14:23 ` David Laight
2023-09-01 14:41 ` Ammar Faizi
2023-09-01 14:54 ` David Laight [this message]
2023-09-01 15:20 ` Ammar Faizi
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