Re: [Qemu-devel] [PATCH] tcg/ppc: Fix failure in tcg_out_mem_long

[Cedric Le Goater <clg@fr.ibm.com>]

On 06/27/2014 06:26 AM, Richard Henderson wrote:
> With rt != r0 on loads, we use rt for scratch.  If we need an index
> register different from base, we can't use rt, but r0 is usable.

That fixes the problem : a x86_64 fedora 20 TCG guest now runs under a 
the latest qemu, (trusty ppc64le host)

Thanks, 

C.


Tested-by: Cédric Le Goater <clg@fr.ibm.com>


> Signed-off-by: Richard Henderson <rth@twiddle.net>
> ---
> This ought to fix the problem that Greg reported.
> 
> That we need to use --enable-debug-tcg to see the assert, and that I
> didn't previously do testing with that is disappointing.  I'm thinking
> that we ought to do something like gcc wrt --enable-checking=release
> vs development, so that we can't do normal development withing these
> asserts enabled.  More on that later...
> 
> 
> r~
> ---
>  tcg/ppc/tcg-target.c | 5 ++++-
>  1 file changed, 4 insertions(+), 1 deletion(-)
> 
> diff --git a/tcg/ppc/tcg-target.c b/tcg/ppc/tcg-target.c
> index c83fd9f..dd84e76 100644
> --- a/tcg/ppc/tcg-target.c
> +++ b/tcg/ppc/tcg-target.c
> @@ -805,7 +805,10 @@ static void tcg_out_mem_long(TCGContext *s, int opi, int opx, TCGReg rt,
> 
>      /* For unaligned, or very large offsets, use the indexed form.  */
>      if (offset & align || offset != (int32_t)offset) {
> -        tcg_debug_assert(rs != base && (!is_store || rs != rt));
> +        if (rs == base) {
> +            rs = TCG_REG_R0;
> +        }
> +        tcg_debug_assert(!is_store || rs != rt);
>          tcg_out_movi(s, TCG_TYPE_PTR, rs, orig);
>          tcg_out32(s, opx | TAB(rt, base, rs));
>          return;
>