Re: [PATCH][SH] simulator mis-executing pre-decrement

[Andrew STUBBS <andrew.stubbs@st.com>]

Ping. No word on this for a week.

Just in case everyone is waiting for the SH maintainer, there is no 
specific maintainer for this simulator, so a global maintainer will be 
required.

Thanks

Andrew STUBBS wrote:
> Hi,
> 
> The attached patch fixes a problem with pre-decrement store instructions 
> on the SH simulator.
> 
> The problem can be demonstrated with the following program:
> 
> #include <stdio.h>
> 
> int
> main()
> {
>     int i[2] = {0,0};
>     int *p = &i[1];
> 
>     asm ("mov.l %0,@-%0\n" : "+r" (p));
> 
>     if ((int*)i[0] == &i[1])
>       printf ("PASS: Value Correct.\n");
>     else
>       printf ("FAIL: Incorrect value written.\n");
> 
>     return 0;
> }
> 
> The issue is that, when both operands use the same register, the *value* 
> to be stored is decremented, but only the *address* of the store should 
> have been decremented. I.e. in the example, it is supposed to store "p" 
> at "p - 4", but actually stores "p - 4" at "p - 4".
> 
> Note that GCC has a similar error which means that the two work together 
> (probably not an accident), but the binaries may not work on real 
> silicon. I think a patch for this problem will be submitted to GCC 
> sometime soon.
> 
> :ADDPATCH sh sim:
> 
> Unfortunately, I can't test it on the latest GDB because CVS isn't 
> accessible (corporate IT issue), but I'm fairly sure it works in the 
> sources I do have. For the same reason, I'll have to ask somebody else 
> to do the commit for me.
> 
> Thanks
> 
> Andrew Stubbs
>