A question about head.S
In arch/ppc/kernel/head.S, there are lines looks like bne 4f or b 5f, I know they are branch instructions, but what about 4f or 5f. Are they the relative length? and what is the unit, I mean if 4f is a number , is it number of instructions or number of bytes or words?
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Quoted 2 lines
From 'info as':
Local Symbol Names
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Local symbols help compilers and programmers use names temporarily.
There are ten local symbol names, which are re-used throughout the program. You may refer to them using the names 0' 1' ... 9'. To define a local symbol, write a label of the form N:' (where N represents any digit). To refer to the most recent previous definition of that symbol write Nb', using the same digit as when you defined the label. To refer to the next definition of a local label, write Nf'--where N gives you a choice of 10 forward references. The b' stands for "backwards" and the f' stands for "forwards".
--
Grant M. Erickson University of Minnesota Alumni
o mail:[email protected] 1996 BSEE
o http://www.tc.umn.edu/~erick205/ 1998 MSEE
Quoted 5 lines · Pei-Jie Hong
In
arch/ppc/kernel/head.S, there are lines looks like bne 4f or b 5f, I know they are branch instructions, but what about 4f or 5f. Are they the relative length? and what is the unit, I mean if 4f is a number , is it number of instructions or number of bytes or words?
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You can use numbers for local (temporary) labels followed by 'f' for forward or 'b' for back. The instruction bne 4f goes to the label '4' further down in the program. If it was bne 4b, it would go to the label '4' previously seen in the file. This is good for short logical jumps and loops. Use the feature with care, massive confusion otherwise ensues.
gvb
Quoted 6 lines · Pei-Jie Hong
In
arch/ppc/kernel/head.S, there are lines looks like bne 4f or b 5f, I know they are branch instructions, but what about 4f or 5f. Are they the relative length? and what is the unit, I mean if 4f is a number , is it number of instructions or number of bytes or words?
** Sent via the linuxppc-embedded mail list. See http://lists.linuxppc.org/
Quoted 6 lines · In message <[email protected]> you wrote:
In
arch/ppc/kernel/head.S, there are lines looks like bne 4f or b 5f, I know they are branch instructions, but what about 4f or 5f. Are they the relative length? and what is the unit, I mean if 4f is a number , is it number of instructions or number of bytes or words?
You will also see labels "4:" and "5:" etc. in the text. "4f" means "label 4 searching forward", while "5b" means "label 5 seaching backwards".
Wolfgang Denk
--
Software Engineering: Embedded and Realtime Systems, Embedded Linux
Phone: (+49)-8142-4596-87 Fax: (+49)-8142-4596-88 Email: [email protected] Heavier than air flying machines are impossible.
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