[Qemu-devel] Re: [PATCH 1/2] target-sparc: Fix -singlestep.

[Blue Swirl <blauwirbel@gmail.com>]

On 4/25/10, Richard Henderson <rth@twiddle.net> wrote:
> Single-stepping was not properly updating npc, resulting in some
>  instructions being executed twice.  In addition, we were emitting
>  dead code at the end of the TB.
>
>  Fix both by teaching gen_goto_tb to avoid goto_tb for single-step
>  and removing the special-case code in gen_intermediate_code_internal.

Nice work!

>  Signed-off-by: Richard Henderson <rth@twiddle.net>
>  ---
>   target-sparc/translate.c |    7 ++++---
>   1 files changed, 4 insertions(+), 3 deletions(-)
>
>  diff --git a/target-sparc/translate.c b/target-sparc/translate.c
>  index b54c520..5162b87 100644
>  --- a/target-sparc/translate.c
>  +++ b/target-sparc/translate.c
>  @@ -81,6 +81,7 @@ typedef struct DisasContext {
>      int address_mask_32bit;
>      uint32_t cc_op;  /* current CC operation */
>      struct TranslationBlock *tb;
>  +    CPUState *env;

Instead of CPUState pointer, please create a flag which combines
env->singlestep_enabled || singlestep.

>      sparc_def_t *def;
>   } DisasContext;
>
>  @@ -234,7 +235,8 @@ static inline void gen_goto_tb(DisasContext *s, int tb_num,
>
>      tb = s->tb;
>      if ((pc & TARGET_PAGE_MASK) == (tb->pc & TARGET_PAGE_MASK) &&
>  -        (npc & TARGET_PAGE_MASK) == (tb->pc & TARGET_PAGE_MASK))  {
>  +        (npc & TARGET_PAGE_MASK) == (tb->pc & TARGET_PAGE_MASK) &&
>  +        !(s->env->singlestep_enabled || singlestep))  {
>          /* jump to same page: we can use a direct jump */
>          tcg_gen_goto_tb(tb_num);
>          tcg_gen_movi_tl(cpu_pc, pc);
>  @@ -4680,6 +4682,7 @@ static inline void gen_intermediate_code_internal(TranslationBlock * tb,
>
>      memset(dc, 0, sizeof(DisasContext));
>      dc->tb = tb;
>  +    dc->env = env;
>      pc_start = tb->pc;
>      dc->pc = pc_start;
>      last_pc = dc->pc;
>  @@ -4755,8 +4758,6 @@ static inline void gen_intermediate_code_internal(TranslationBlock * tb,
>          /* if single step mode, we generate only one instruction and
>             generate an exception */
>          if (env->singlestep_enabled || singlestep) {
>  -            tcg_gen_movi_tl(cpu_pc, dc->pc);
>  -            tcg_gen_exit_tb(0);
>              break;
>          }
>      } while ((gen_opc_ptr < gen_opc_end) &&
>
> --
>  1.6.6.1
>
>