Re: [Qemu-devel] [PATCH target-arm] Don' use T[x] in helper

[Laurent Desnogues]

2009/3/24 Torbjörn Andersson <address@hidden>:
>
> I hit a strange issue with add_cc, can't really explain how it appeared but
> it did. The patch below solved my problem.
>
> Can someone make a qualified guess why? I'm compling with gcc 4.
>
> However, T0 and T1 in a helper should not be used, because it creates a
> unnecessary dependency between translate.c and op_helper.c. Am I correct?
>
> Further, if we cannot trust T0 and T1 in a helper, what about the global
> env-variable?

Your patch is correct and the previous code works by accident
since add_cc is called this way:

   gen_helper_add_cc(cpu_T[0], cpu_T[0], cpu_T[1])

What I find strange is that you had issue with the code in svn.  I
didn't have before I fixed it, but it was perhaps using some old
compiler at that time.


Laurent

Acked-by: Laurent Desnogues <address@hidden>

> /Best regards Torbjörn Andersson
>
> Index: op_helper.c
> ===================================================================
> --- op_helper.c (revision 6883)
> +++ op_helper.c (working copy)
> @@ -307,7 +307,7 @@
>  uint32_t HELPER (add_cc)(uint32_t a, uint32_t b)
>  {
>     uint32_t result;
> -    result = T0 + T1;
> +    result = a + b;
>     env->NF = env->ZF = result;
>     env->CF = result < a;
>     env->VF = (a ^ b ^ -1) & (a ^ result);