From: "Andrew Lynch" <andrew.lynch@knuut.de>
To: Fans of the OS Plan 9 from Bell Labs <9fans@cse.psu.edu>
Subject: Re: [9fans] which register is used as FP on the x86
Date: Sat, 26 Jun 2004 13:56:04 +0200 [thread overview]
Message-ID: <1040626135604.ZM882@Sindy> (raw)
In-Reply-To: rog@vitanuova.com "Re: [9fans] which register is used as FP on the x86" (Jun 25, 6:53pm)
On Jun 25, 6:53pm, rog@vitanuova.com wrote:
> no register is dedicated as a frame pointer.
>
> if you know the PC, you can find out the FP from the SP.
Maybe not dedicated, in the sense that you can also use it for other stuff, but
the EBP register is intended to be used as FP:
"3. Stack-Frame Base Pointer (EBP) Register: The EBP register typically is used
to access data structures passed on the stack. [...] If the stack pointer is
copied into the base pointer before anything is pushed on the stack, the base
pointer can be used to reference data structures with fixed offsets. [...]
Instructions, such as ENTER and LEAVE instructions, are provided which
automatically set up the EBP register for convenient access to variables."
intel 386DX Microprocessor Programmer's Reference Manual 1990
Andrew.
P.S. If you have a gcc targeted for x86 you can see for yourself by comparing
the output of "gcc -S" with "gcc -fomit-frame-pointer -S".
next prev parent reply other threads:[~2004-06-26 11:56 UTC|newest]
Thread overview: 12+ messages / expand[flat|nested] mbox.gz Atom feed top
2004-06-25 17:30 ron minnich
2004-06-25 17:53 ` rog
2004-06-26 11:56 ` Andrew Lynch [this message]
2004-06-26 12:35 ` Latchesar Ionkov
2004-06-26 12:35 ` Charles Forsyth
2004-06-26 14:27 ` Latchesar Ionkov
2004-06-26 17:31 ` Charles Forsyth
2004-07-03 7:17 ` [9fans] cpuserver: dhcp for authsrv, rio, users, ssh, factotum, pull Stephen Wynne
2004-07-03 16:37 ` [9fans] andrey mirtchovski
2004-07-05 4:06 ` [9fans] Stephen Wynne
2004-07-05 17:23 ` [9fans] andrey mirtchovski
2004-07-05 20:33 ` [9fans] Eric Grosse
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