[sdcc-devel] [ sdcc-Bugs-3538844 ] --reserve-regs-iy not working

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Bugs item #3538844, was opened at 2012-06-28 16:33
Message generated for change (Comment added) made by chastai
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Category: z80 port
Group: None
Status: Open
Resolution: None
Priority: 5
Private: No
Submitted By: https://www.google.com/accounts ()
Assigned to: Philipp Klaus Krause (spth)
Summary: --reserve-regs-iy not working

Initial Comment:
Generated assembly still appears to use IY even when --reserve-regs-iy is passed.

Command:
sdcc -mz80 --reserve-regs-iy -L ./sdcc/lib/z80 main.c

Version:
3.2.0 #7971 (Jun 26 2012) (Mac OS X i386)

Here is part of the generated main.asm:

;main.c:2: return 8 - (a / 8);
	ld	iy,#2
	add	iy,sp
	ld	d,0 (iy)
	bit	7, d
	jr	Z,00103$
	ld	a,d
	add	a, #0x07
	ld	d,a

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Comment By: Christophe Staïesse (chastai)
Date: 2012-06-29 14:05

Message:
Thanks for the fix! It works better but there is still at least a case
where IY is used : 

After some experiments, I've noticed that IY is used to clean up the stack
when calling a function where 
-the sum of the sizes of the parameters are at least 9 bytes (i.e.
f(int,int,int,int,char) or f(long long, char), ...) 
-the return type is integer
-the return value is used by the callee.

example :
  
extern f(char a, char b, char c, char d, char e, char f, char g, char h,
char i);
main()
{
    f(1,2,3,4,5,6,7,8,9); /* the return value in HL is ignored -> HL is
selected to clean up the call stack */
    return f(1,2,3,4,5,6,7,8,9); /* the return value in HL is used -> IY is
selected to clean up the stack */ 
}

In the library this bug affects _divslonglong.c, _divulonglong.c,
_rlslonglong. 

Christophe.

----------------------------------------------------------------------

Comment By: Philipp Klaus Krause (spth)
Date: 2012-06-29 01:47

Message:
I thought I had fixed this when I fixed #3536902 . Unfortunately, it seems
there's no time left before the release, but I'll fix it after that.

The fix is simple:

Change line 1472 in src/z80/alloc2.cc from "if(IS_GB)" to "if(IS_GB ||
IY_RESERVED)".

Philipp

P.S.:The fix is only sufficient for functions that have at most 126 bytes
of parameters and at most 127 bytes of local variables. Other functions
will still use iy.


----------------------------------------------------------------------

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