Re: Wanted: A decent assembler

* Re: Wanted: A decent assembler
@ 2003-04-23 13:02 Chuck Ebbert
  2003-04-23 13:57 ` Maciej W. Rozycki
  0 siblings, 1 reply; 6+ messages in thread
From: Chuck Ebbert @ 2003-04-23 13:02 UTC (permalink / raw)
  To: root; +Cc: linux-kernel

"Richard B. Johnson" wrote"

>>   Output from 'make bzImage' after making some changes:
>>
>>         Error: non-constant expression in ".if" statement.
>>
>>
>>   Why is the kernel using a 1-pass assembler?
>>
>
> Well it isn't. The AT&T clone assembler will resolve forward
> references and it does it by using as many passes as necessary.
> It even has a 'reasonable' MACRO capability. I use it quite a
> bit to minimize the code-size or to maximize performance in
> embedded systems.

  This is from the info for GNU as:

   "The result of an expression must be an absolute number, or else an
offset into a particular section.  If an expression is not absolute,
and there is not enough information when `as' sees the expression to
know its section, a second pass over the source program might be
necessary to interpret the expression--but the second pass is currently
not implemented.  `as' aborts with an error message in this situation."

> Your error shown above is a real error. If you expose the code
> that it barfed on, maybe somebody could help you fix the code.

if NR_IRQS gt 16			# only build this for IO-APIC
	.align 8,0x90			# make ENTRY have exact address
irq_align=8				# start with 8-byte alignment
ENTRY(high_irq_entries_start)
rept NR_IRQS-16			# the rest of the stubs
	.align irq_align,0x90
1:	pushl $vector-256		# 5-byte instruction
	jmp common_interrupt		# 2 or 5 bytes (8 or 32-bit offset)
2:
if 2b-1b > 8			# <============================= ERROR
	irq_align=16			# switch to 16-byte alignment
endif
data
	.long 1b
text
vector=vector+1
endr
endif

-------
 Chuck

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