| Message ID | 20210630183226.3290849-6-richard.henderson@linaro.org (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | accel/tcg: Introduce translator_use_goto_tb | expand |
On Wed, 30 Jun 2021 at 19:47, Richard Henderson <richard.henderson@linaro.org> wrote: > > Using gen_goto_tb directly misses the single-step check. > > Cc: qemu-arm@nongnu.org > Signed-off-by: Richard Henderson <richard.henderson@linaro.org> > --- > target/arm/translate.c | 4 ++-- > 1 file changed, 2 insertions(+), 2 deletions(-) > > diff --git a/target/arm/translate.c b/target/arm/translate.c > index a0c6cfa902..8cd31feeaa 100644 > --- a/target/arm/translate.c > +++ b/target/arm/translate.c > @@ -8582,7 +8582,7 @@ static bool trans_ISB(DisasContext *s, arg_ISB *a) > * self-modifying code correctly and also to take > * any pending interrupts immediately. > */ > - gen_goto_tb(s, 0, s->base.pc_next); > + gen_jmp(s, s->base.pc_next); > return true; > } > > @@ -8596,7 +8596,7 @@ static bool trans_SB(DisasContext *s, arg_SB *a) > * for TCG; MB and end the TB instead. > */ > tcg_gen_mb(TCG_MO_ALL | TCG_BAR_SC); > - gen_goto_tb(s, 0, s->base.pc_next); > + gen_jmp(s, s->base.pc_next); > return true; Why isn't it enough here just to set is_jmp to DISAS_NEXT ? thanks -- PMM
On 7/8/21 5:05 AM, Peter Maydell wrote: > On Wed, 30 Jun 2021 at 19:47, Richard Henderson > <richard.henderson@linaro.org> wrote: >> >> Using gen_goto_tb directly misses the single-step check. >> >> Cc: qemu-arm@nongnu.org >> Signed-off-by: Richard Henderson <richard.henderson@linaro.org> >> --- >> target/arm/translate.c | 4 ++-- >> 1 file changed, 2 insertions(+), 2 deletions(-) >> >> diff --git a/target/arm/translate.c b/target/arm/translate.c >> index a0c6cfa902..8cd31feeaa 100644 >> --- a/target/arm/translate.c >> +++ b/target/arm/translate.c >> @@ -8582,7 +8582,7 @@ static bool trans_ISB(DisasContext *s, arg_ISB *a) >> * self-modifying code correctly and also to take >> * any pending interrupts immediately. >> */ >> - gen_goto_tb(s, 0, s->base.pc_next); >> + gen_jmp(s, s->base.pc_next); >> return true; >> } >> >> @@ -8596,7 +8596,7 @@ static bool trans_SB(DisasContext *s, arg_SB *a) >> * for TCG; MB and end the TB instead. >> */ >> tcg_gen_mb(TCG_MO_ALL | TCG_BAR_SC); >> - gen_goto_tb(s, 0, s->base.pc_next); >> + gen_jmp(s, s->base.pc_next); >> return true; > > Why isn't it enough here just to set is_jmp to DISAS_NEXT ? You mean DISAS_TOO_MANY? That would work, yes. At the time I was just thinking of replacing one jump with another. r~
On Thu, 8 Jul 2021 at 17:04, Richard Henderson <richard.henderson@linaro.org> wrote: > > On 7/8/21 5:05 AM, Peter Maydell wrote: > > On Wed, 30 Jun 2021 at 19:47, Richard Henderson > > <richard.henderson@linaro.org> wrote: > >> > >> Using gen_goto_tb directly misses the single-step check. > >> > >> Cc: qemu-arm@nongnu.org > >> Signed-off-by: Richard Henderson <richard.henderson@linaro.org> > >> --- > >> target/arm/translate.c | 4 ++-- > >> 1 file changed, 2 insertions(+), 2 deletions(-) > >> > >> diff --git a/target/arm/translate.c b/target/arm/translate.c > >> index a0c6cfa902..8cd31feeaa 100644 > >> --- a/target/arm/translate.c > >> +++ b/target/arm/translate.c > >> @@ -8582,7 +8582,7 @@ static bool trans_ISB(DisasContext *s, arg_ISB *a) > >> * self-modifying code correctly and also to take > >> * any pending interrupts immediately. > >> */ > >> - gen_goto_tb(s, 0, s->base.pc_next); > >> + gen_jmp(s, s->base.pc_next); > >> return true; > >> } > >> > >> @@ -8596,7 +8596,7 @@ static bool trans_SB(DisasContext *s, arg_SB *a) > >> * for TCG; MB and end the TB instead. > >> */ > >> tcg_gen_mb(TCG_MO_ALL | TCG_BAR_SC); > >> - gen_goto_tb(s, 0, s->base.pc_next); > >> + gen_jmp(s, s->base.pc_next); > >> return true; > > > > Why isn't it enough here just to set is_jmp to DISAS_NEXT ? > > You mean DISAS_TOO_MANY? That would work, yes. > At the time I was just thinking of replacing one jump with another. You've implicitly answered my question, which is that the main translator loop code treats DISAS_NEXT as "keep adding insns to the TB" :-) It feels slightly like misuse to use DISAS_TOO_MANY, unless we renamed it to something like DISAS_END_TB (which is what it's actually doing). thanks -- PMM
On 7/8/21 9:11 AM, Peter Maydell wrote: >>> Why isn't it enough here just to set is_jmp to DISAS_NEXT ? >> >> You mean DISAS_TOO_MANY? That would work, yes. >> At the time I was just thinking of replacing one jump with another. > > You've implicitly answered my question, which is that the main > translator loop code treats DISAS_NEXT as "keep adding insns to > the TB" :-) > > It feels slightly like misuse to use DISAS_TOO_MANY, unless we > renamed it to something like DISAS_END_TB (which is what it's > actually doing). Yeah, better naming would have been a good. In this instance I think I chose an odd colour for the bike shed. The problem with just DISAS_END_TB is that there are many ways to end a tb, with at least: (1) goto_tb next, (2) goto_ptr next, (3) exit_tb. We wind up replicating these three across many of the targets, so it would be a really nice cleanup to standardize, and with good names. r~
On Thu, 8 Jul 2021 at 17:17, Richard Henderson <richard.henderson@linaro.org> wrote: > > On 7/8/21 9:11 AM, Peter Maydell wrote: > >>> Why isn't it enough here just to set is_jmp to DISAS_NEXT ? > >> > >> You mean DISAS_TOO_MANY? That would work, yes. > >> At the time I was just thinking of replacing one jump with another. > > > > You've implicitly answered my question, which is that the main > > translator loop code treats DISAS_NEXT as "keep adding insns to > > the TB" :-) > > > > It feels slightly like misuse to use DISAS_TOO_MANY, unless we > > renamed it to something like DISAS_END_TB (which is what it's > > actually doing). > > Yeah, better naming would have been a good. In this instance I think I chose an odd > colour for the bike shed. > > The problem with just DISAS_END_TB is that there are many ways to end a tb, with at least: > (1) goto_tb next, (2) goto_ptr next, (3) exit_tb. We wind up replicating these three > across many of the targets, so it would be a really nice cleanup to standardize, and with > good names. Mmm. Anyway, for this change Reviewed-by: Peter Maydell <peter.maydell@linaro.org> thanks -- PMM
diff --git a/target/arm/translate.c b/target/arm/translate.c index a0c6cfa902..8cd31feeaa 100644 --- a/target/arm/translate.c +++ b/target/arm/translate.c @@ -8582,7 +8582,7 @@ static bool trans_ISB(DisasContext *s, arg_ISB *a) * self-modifying code correctly and also to take * any pending interrupts immediately. */ - gen_goto_tb(s, 0, s->base.pc_next); + gen_jmp(s, s->base.pc_next); return true; } @@ -8596,7 +8596,7 @@ static bool trans_SB(DisasContext *s, arg_SB *a) * for TCG; MB and end the TB instead. */ tcg_gen_mb(TCG_MO_ALL | TCG_BAR_SC); - gen_goto_tb(s, 0, s->base.pc_next); + gen_jmp(s, s->base.pc_next); return true; }
Using gen_goto_tb directly misses the single-step check. Cc: qemu-arm@nongnu.org Signed-off-by: Richard Henderson <richard.henderson@linaro.org> --- target/arm/translate.c | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-)