[sdcc-devel] [ sdcc-Bugs-2646174 ] dest parameter for memcpy/ldir garbled

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Bugs item #2646174, was opened at 2009-02-27 19:30
Message generated for change (Comment added) made by arniml
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Category: z80 port
Group: None
Status: Open
Resolution: None
Priority: 5
Private: No
Submitted By: Arnim Läuger (arniml)
Assigned to: Nobody/Anonymous (nobody)
Summary: dest parameter for memcpy/ldir garbled

Initial Comment:
I ran into a problem where the compiler generates wrong code when calling memcpy().
It occurs at line 850 in tff.c which is compiled to a series of ld as seen in tff_ref.asm, line 3689 onwards:

;tff.c:850: memcpy(&dir[DIR_Name], fn, 8+3);
	ld	l,-16 (ix)
	ld	h,-15 (ix)
-> prepares the dest pointer in hl
	ld	hl,#0x0010
	add	hl,sp
-> overwrites the dest pointer with src pointer
	ld	c,l
	ld	b,h
-> set src bc for ldir
	ex	de,hl
-> set dest hl for ldir, same as src now!
	ld	l,c
	ld	h,b
	ld	bc,#0x000B
	ldir
-> won't memcpy as expected

If fn is replaced with a plain string, everything works fine.

The issue was found with sdcc Version 2.8.9 #5361 and is also present in latest Version 2.8.9 #5390 (Feb 27 2009) (UNIX), sdcc-snapshot-i386-unknown-linux2.5-20090227-5390.tar.bz2.

It should be reproducible with the attached archive. Unpack and 'make'.

Best regards
Arnim


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>Comment By: Arnim Läuger (arniml)
Date: 2009-02-28 20:17

Message:
Is there anything I can do to work around this issue? I'm kind of stuck
with the software for this embedded project.

Arnim


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Comment By: Philipp Krause (spth)
Date: 2009-02-28 16:56

Message:
I meant "genAddrOf" instead of "genPointer".

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Comment By: Philipp Krause (spth)
Date: 2009-02-28 16:56

Message:
As the asm generated using --fverbose-asm shows, the problem is not
directly in the (relatively new) implementation of memcpy() as builtin, but
more complicated: A genAssign moves dest into hl, but a genPointer
immediately overwrites it with src.

;tff.c:850: memcpy(&dir[DIR_Name], fn, 8+3);
;	genAssign
;	AOP_STK for _f_open_dir_1_1
	ld	l,-16 (ix)
	ld	h,-15 (ix)
;	genAddrOf
	ld	hl,#0x0010
	add	hl,sp
	ld	c,l
	ld	b,h
;	genBuiltIn
; _saveRegsForCall: sendSetSize: 0 deInUse: 0 bcInUse: 0 deSending: 0
; peephole 81 used ex to load hl into de.
	ex	de,hl
	ld	l,c
	ld	h,b
	ld	bc,#0x000B
	ldir


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