| Message ID | 20231014100121.109817-14-pbonzini@redhat.com |
|---|---|
| State | New |
| Headers | show |
| Series | target/i386: decoder changes for 8.2 | expand |
On 10/14/23 03:01, Paolo Bonzini wrote: > The new x86 decoder wants to compute EFLAGS before writeback, which > can be an issue for some instructions such as ARPL. Extract code > to compute the EFLAGS without clobbering CC_SRC, in case the ARPL > memory write causes a fault. > > Signed-off-by: Paolo Bonzini <pbonzini@redhat.com> > --- > target/i386/tcg/translate.c | 18 +++++++++++++----- > 1 file changed, 13 insertions(+), 5 deletions(-) > > diff --git a/target/i386/tcg/translate.c b/target/i386/tcg/translate.c > index e13bf7df591..2da7c357cdc 100644 > --- a/target/i386/tcg/translate.c > +++ b/target/i386/tcg/translate.c > @@ -872,18 +872,20 @@ static void gen_op_update_neg_cc(DisasContext *s) > tcg_gen_movi_tl(s->cc_srcT, 0); > } > > -/* compute all eflags to cc_src */ > -static void gen_compute_eflags(DisasContext *s) > +/* compute all eflags to reg */ > +static void gen_mov_eflags(DisasContext *s, TCGv reg) > { > TCGv zero, dst, src1, src2; > int live, dead; > > if (s->cc_op == CC_OP_EFLAGS) { > + if (reg != cpu_cc_src) { > + tcg_gen_mov_tl(reg, cpu_cc_src); > + } tcg_gen_mov_tl already takes care of eliding the nop move. > return; > } > if (s->cc_op == CC_OP_CLR) { > - tcg_gen_movi_tl(cpu_cc_src, CC_Z | CC_P); > - set_cc_op(s, CC_OP_EFLAGS); > + tcg_gen_movi_tl(reg, CC_Z | CC_P); > return; > } > > @@ -909,7 +911,13 @@ static void gen_compute_eflags(DisasContext *s) > } > > gen_update_cc_op(s); > - gen_helper_cc_compute_all(cpu_cc_src, dst, src1, src2, cpu_cc_op); > + gen_helper_cc_compute_all(reg, dst, src1, src2, cpu_cc_op); > +} You don't want to gen_update_cc_op. I think you want TCGv_i32 cc_op = cpu_cc_op; if (s->cc_op != CC_OP_DYNAMIC) cc_op = tcg_constant_i32(s->cc_op); gen_helper_cc_compute_all(..., cc_op); No write to cpu_cc_op required at all, since... > +/* compute all eflags to cc_src */ > +static void gen_compute_eflags(DisasContext *s) > +{ > + gen_mov_eflags(s, cpu_cc_src); > set_cc_op(s, CC_OP_EFLAGS); > } ... this will modify it again anyway. r~
diff --git a/target/i386/tcg/translate.c b/target/i386/tcg/translate.c index e13bf7df591..2da7c357cdc 100644 --- a/target/i386/tcg/translate.c +++ b/target/i386/tcg/translate.c @@ -872,18 +872,20 @@ static void gen_op_update_neg_cc(DisasContext *s) tcg_gen_movi_tl(s->cc_srcT, 0); } -/* compute all eflags to cc_src */ -static void gen_compute_eflags(DisasContext *s) +/* compute all eflags to reg */ +static void gen_mov_eflags(DisasContext *s, TCGv reg) { TCGv zero, dst, src1, src2; int live, dead; if (s->cc_op == CC_OP_EFLAGS) { + if (reg != cpu_cc_src) { + tcg_gen_mov_tl(reg, cpu_cc_src); + } return; } if (s->cc_op == CC_OP_CLR) { - tcg_gen_movi_tl(cpu_cc_src, CC_Z | CC_P); - set_cc_op(s, CC_OP_EFLAGS); + tcg_gen_movi_tl(reg, CC_Z | CC_P); return; } @@ -909,7 +911,13 @@ static void gen_compute_eflags(DisasContext *s) } gen_update_cc_op(s); - gen_helper_cc_compute_all(cpu_cc_src, dst, src1, src2, cpu_cc_op); + gen_helper_cc_compute_all(reg, dst, src1, src2, cpu_cc_op); +} + +/* compute all eflags to cc_src */ +static void gen_compute_eflags(DisasContext *s) +{ + gen_mov_eflags(s, cpu_cc_src); set_cc_op(s, CC_OP_EFLAGS); }
The new x86 decoder wants to compute EFLAGS before writeback, which can be an issue for some instructions such as ARPL. Extract code to compute the EFLAGS without clobbering CC_SRC, in case the ARPL memory write causes a fault. Signed-off-by: Paolo Bonzini <pbonzini@redhat.com> --- target/i386/tcg/translate.c | 18 +++++++++++++----- 1 file changed, 13 insertions(+), 5 deletions(-)