target/i386/tcg/fpu_helper.c | 4 ++++ 1 file changed, 4 insertions(+)
The instruction description says "It is loaded without rounding
errors." which implies we should have the widest rounding mode
possible.
Resolves: https://gitlab.com/qemu-project/qemu/-/issues/888
Signed-off-by: Alex Bennée <alex.bennee@linaro.org>
---
target/i386/tcg/fpu_helper.c | 4 ++++
1 file changed, 4 insertions(+)
diff --git a/target/i386/tcg/fpu_helper.c b/target/i386/tcg/fpu_helper.c
index cdd8e9f947..d986fd5792 100644
--- a/target/i386/tcg/fpu_helper.c
+++ b/target/i386/tcg/fpu_helper.c
@@ -250,11 +250,15 @@ void helper_fildl_ST0(CPUX86State *env, int32_t val)
void helper_fildll_ST0(CPUX86State *env, int64_t val)
{
int new_fpstt;
+ FloatX80RoundPrec old = get_floatx80_rounding_precision(&env->fp_status);
+ set_floatx80_rounding_precision(floatx80_precision_x, &env->fp_status);
new_fpstt = (env->fpstt - 1) & 7;
env->fpregs[new_fpstt].d = int64_to_floatx80(val, &env->fp_status);
env->fpstt = new_fpstt;
env->fptags[new_fpstt] = 0; /* validate stack entry */
+
+ set_floatx80_rounding_precision(old, &env->fp_status);
}
uint32_t helper_fsts_ST0(CPUX86State *env)
--
2.30.2
On 3/7/22 08:44, Alex Bennée wrote:
> The instruction description says "It is loaded without rounding
> errors." which implies we should have the widest rounding mode
> possible.
>
> Resolves: https://gitlab.com/qemu-project/qemu/-/issues/888
> Signed-off-by: Alex Bennée <alex.bennee@linaro.org>
> ---
> target/i386/tcg/fpu_helper.c | 4 ++++
> 1 file changed, 4 insertions(+)
>
> diff --git a/target/i386/tcg/fpu_helper.c b/target/i386/tcg/fpu_helper.c
> index cdd8e9f947..d986fd5792 100644
> --- a/target/i386/tcg/fpu_helper.c
> +++ b/target/i386/tcg/fpu_helper.c
> @@ -250,11 +250,15 @@ void helper_fildl_ST0(CPUX86State *env, int32_t val)
> void helper_fildll_ST0(CPUX86State *env, int64_t val)
> {
> int new_fpstt;
> + FloatX80RoundPrec old = get_floatx80_rounding_precision(&env->fp_status);
> + set_floatx80_rounding_precision(floatx80_precision_x, &env->fp_status);
>
> new_fpstt = (env->fpstt - 1) & 7;
> env->fpregs[new_fpstt].d = int64_to_floatx80(val, &env->fp_status);
> env->fpstt = new_fpstt;
> env->fptags[new_fpstt] = 0; /* validate stack entry */
> +
> + set_floatx80_rounding_precision(old, &env->fp_status);
> }
Yep.
Need a similar fix for fildl_ST0, for the case floatx80_precision_s is currently set
(int32_t has more than the 23 bits of single-precision).
r~
Richard Henderson <richard.henderson@linaro.org> writes:
> On 3/7/22 08:44, Alex Bennée wrote:
>> The instruction description says "It is loaded without rounding
>> errors." which implies we should have the widest rounding mode
>> possible.
>> Resolves: https://gitlab.com/qemu-project/qemu/-/issues/888
>> Signed-off-by: Alex Bennée <alex.bennee@linaro.org>
>> ---
>> target/i386/tcg/fpu_helper.c | 4 ++++
>> 1 file changed, 4 insertions(+)
>> diff --git a/target/i386/tcg/fpu_helper.c
>> b/target/i386/tcg/fpu_helper.c
>> index cdd8e9f947..d986fd5792 100644
>> --- a/target/i386/tcg/fpu_helper.c
>> +++ b/target/i386/tcg/fpu_helper.c
>> @@ -250,11 +250,15 @@ void helper_fildl_ST0(CPUX86State *env, int32_t val)
>> void helper_fildll_ST0(CPUX86State *env, int64_t val)
>> {
>> int new_fpstt;
>> + FloatX80RoundPrec old = get_floatx80_rounding_precision(&env->fp_status);
>> + set_floatx80_rounding_precision(floatx80_precision_x, &env->fp_status);
>> new_fpstt = (env->fpstt - 1) & 7;
>> env->fpregs[new_fpstt].d = int64_to_floatx80(val, &env->fp_status);
>> env->fpstt = new_fpstt;
>> env->fptags[new_fpstt] = 0; /* validate stack entry */
>> +
>> + set_floatx80_rounding_precision(old, &env->fp_status);
>> }
>
> Yep.
>
> Need a similar fix for fildl_ST0, for the case floatx80_precision_s is
> currently set (int32_t has more than the 23 bits of single-precision).
It can't hurt to convert with:
set_floatx80_rounding_precision(floatx80_precision_x, &env->fp_status);
in that case as well right?
--8<---------------cut here---------------start------------->8---
target/i386: for maximum rounding precision for fildll
The instruction description says "It is loaded without rounding
errors." which implies we should have the widest rounding mode
possible.
Resolves: https://gitlab.com/qemu-project/qemu/-/issues/888
Signed-off-by: Alex Bennée <alex.bennee@linaro.org>
1 file changed, 13 insertions(+)
target/i386/tcg/fpu_helper.c | 13 +++++++++++++
modified target/i386/tcg/fpu_helper.c
@@ -237,24 +237,37 @@ void helper_fldl_ST0(CPUX86State *env, uint64_t val)
merge_exception_flags(env, old_flags);
}
+static FloatX80RoundPrec tmp_maximise_precision(float_status *st)
+{
+ FloatX80RoundPrec old = get_floatx80_rounding_precision(st);
+ set_floatx80_rounding_precision(floatx80_precision_x, st);
+ return old;
+}
+
void helper_fildl_ST0(CPUX86State *env, int32_t val)
{
int new_fpstt;
+ FloatX80RoundPrec old = tmp_maximise_precision(&env->fp_status);
new_fpstt = (env->fpstt - 1) & 7;
env->fpregs[new_fpstt].d = int32_to_floatx80(val, &env->fp_status);
env->fpstt = new_fpstt;
env->fptags[new_fpstt] = 0; /* validate stack entry */
+
+ set_floatx80_rounding_precision(old, &env->fp_status);
}
void helper_fildll_ST0(CPUX86State *env, int64_t val)
{
int new_fpstt;
+ FloatX80RoundPrec old = tmp_maximise_precision(&env->fp_status);
new_fpstt = (env->fpstt - 1) & 7;
env->fpregs[new_fpstt].d = int64_to_floatx80(val, &env->fp_status);
env->fpstt = new_fpstt;
env->fptags[new_fpstt] = 0; /* validate stack entry */
+
+ set_floatx80_rounding_precision(old, &env->fp_status);
}
--8<---------------cut here---------------end--------------->8---
>
>
> r~
--
Alex Bennée
On 3/7/22 10:48, Alex Bennée wrote: >> Need a similar fix for fildl_ST0, for the case floatx80_precision_s is >> currently set (int32_t has more than the 23 bits of single-precision). > > It can't hurt to convert with: > > set_floatx80_rounding_precision(floatx80_precision_x, &env->fp_status); > > in that case as well right? s/can't hurt/is required/ was my point. Followup patch looks good: Reviewed-by: Richard Henderson <richard.henderson@linaro.org> r~
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