On Fri, Apr 09, 2010 at 05:28:40PM +0200, Stefan Weil wrote:
> Register fp (frame pointer) is a bad choice for compilations
> without optimisation, because the compiler makes heavy use
> of this register (so the resulting code crashes).
>
> Register s0 had been used for TCG_AREG1 in earlier releases,
> but was no longer used and is now free for TCG_AREG0.
>
> The resulting code works for compilations without
> optimisation (tested with qemu mips in qemu mips
> on x86 host).
>
> v2:
>
> * Remove s0 from tcg_target_callee_save_regs and add fp there.
> Hint from Aurelien Jarno, thanks.
>
> * Add fp to list of reserved registers.
>
> v3:
>
> * Don't add fp to list of reserved registers
> Thanks to Richard Henderson.
>
> * Remove s0 from tcg_target_reg_alloc_order.
>
> Cc: Aurelien Jarno <aurel...@aurel32.net>
> Cc: Richard Henderson <r...@twiddle.net>
> Signed-off-by: Stefan Weil <w...@mail.berlios.de>
> ---
> dyngen-exec.h | 2 +-
> tcg/mips/tcg-target.c | 7 +++++--
> tcg/mips/tcg-target.h | 2 +-
> 3 files changed, 7 insertions(+), 4 deletions(-)
>
> diff --git a/dyngen-exec.h b/dyngen-exec.h
> index d04eda8..0700a2d 100644
> --- a/dyngen-exec.h
> +++ b/dyngen-exec.h
> @@ -59,7 +59,7 @@ extern int printf(const char *, ...);
> #elif defined(__hppa__)
> #define AREG0 "r17"
> #elif defined(__mips__)
> -#define AREG0 "fp"
> +#define AREG0 "s0"
> #elif defined(__sparc__)
> #ifdef CONFIG_SOLARIS
> #define AREG0 "g2"
> diff --git a/tcg/mips/tcg-target.c b/tcg/mips/tcg-target.c
> index f4fb615..31296fc 100644
> --- a/tcg/mips/tcg-target.c
> +++ b/tcg/mips/tcg-target.c
> @@ -69,7 +69,9 @@ static const char * const
> tcg_target_reg_names[TCG_TARGET_NB_REGS] = {
>
> /* check if we really need so many registers :P */
> static const int tcg_target_reg_alloc_order[] = {
> +#if 0 /* used for the global env (TCG_AREG0), so don't use it here */
> TCG_REG_S0,
> +#endif
This is not something necessary. The fact this register is declared as
TCG_AREG0, will make TCG skip this automatically.
> TCG_REG_S1,
> TCG_REG_S2,
> TCG_REG_S3,
> @@ -1450,7 +1452,9 @@ static const TCGTargetOpDef mips_op_defs[] = {
> };
>
> static int tcg_target_callee_save_regs[] = {
> +#if 0 /* used for the global env (TCG_AREG0), so no need to save */
> TCG_REG_S0,
> +#endif
> TCG_REG_S1,
> TCG_REG_S2,
> TCG_REG_S3,
> @@ -1459,8 +1463,7 @@ static int tcg_target_callee_save_regs[] = {
> TCG_REG_S6,
> TCG_REG_S7,
> TCG_REG_GP,
> - /* TCG_REG_FP, */ /* currently used for the global env, so np
> - need to save */
> + TCG_REG_FP,
> TCG_REG_RA, /* should be last for ABI compliance */
> };
>
> diff --git a/tcg/mips/tcg-target.h b/tcg/mips/tcg-target.h
> index 0292d33..0028bfa 100644
> --- a/tcg/mips/tcg-target.h
> +++ b/tcg/mips/tcg-target.h
> @@ -97,7 +97,7 @@ enum {
> #undef TCG_TARGET_HAS_ext16u_i32 /* andi rt, rs, 0xffff */
>
> /* Note: must be synced with dyngen-exec.h */
> -#define TCG_AREG0 TCG_REG_FP
> +#define TCG_AREG0 TCG_REG_S0
>
> /* guest base is supported */
> #define TCG_TARGET_HAS_GUEST_BASE
> --
> 1.7.0
>
>
--
Aurelien Jarno GPG: 1024D/F1BCDB73
aurel...@aurel32.net http://www.aurel32.net
