[PATCH 2/2] target/ppc: Bugfix FP when OE/UE are set

Lucas Mateus Castro(alqotel) posted 2 patches 1 month, 3 weeks ago
Maintainers: Aurelien Jarno <aurelien@aurel32.net>, Peter Maydell <peter.maydell@linaro.org>, "Alex Bennée" <alex.bennee@linaro.org>, "Cédric Le Goater" <clg@kaod.org>, Daniel Henrique Barboza <danielhb413@gmail.com>, David Gibson <david@gibson.dropbear.id.au>, Greg Kurz <groug@kaod.org>
[PATCH 2/2] target/ppc: Bugfix FP when OE/UE are set
Posted by Lucas Mateus Castro(alqotel) 1 month, 3 weeks ago
From: "Lucas Mateus Castro (alqotel)" <lucas.araujo@eldorado.org.br>

When an overflow exception occurs and OE is set the intermediate result
should be adjusted (by subtracting from the exponent) to avoid rounding
to inf. The same applies to an underflow exceptionion and UE (but adding
to the exponent). To do this set the fp_status.rebias_overflow when OE
is set and fp_status.rebias_underflow when UE is set as the FPU will
recalculate in case of a overflow/underflow if the according rebias* is
set.

Signed-off-by: Lucas Mateus Castro (alqotel) <lucas.araujo@eldorado.org.br>
---
 target/ppc/cpu.c        | 2 ++
 target/ppc/fpu_helper.c | 2 --
 2 files changed, 2 insertions(+), 2 deletions(-)

diff --git a/target/ppc/cpu.c b/target/ppc/cpu.c
index 401b6f9e63..0ebac04bc4 100644
--- a/target/ppc/cpu.c
+++ b/target/ppc/cpu.c
@@ -120,6 +120,8 @@ void ppc_store_fpscr(CPUPPCState *env, target_ulong val)
         val |= FP_FEX;
     }
     env->fpscr = val;
+    env->fp_status.rebias_overflow  = (FP_OE & env->fpscr) ? true : false;
+    env->fp_status.rebias_underflow = (FP_UE & env->fpscr) ? true : false;
     if (tcg_enabled()) {
         fpscr_set_rounding_mode(env);
     }
diff --git a/target/ppc/fpu_helper.c b/target/ppc/fpu_helper.c
index 134804628b..c17575de5d 100644
--- a/target/ppc/fpu_helper.c
+++ b/target/ppc/fpu_helper.c
@@ -344,7 +344,6 @@ static inline int float_overflow_excp(CPUPPCState *env)
 
     bool overflow_enabled = !!(env->fpscr & FP_OE);
     if (overflow_enabled) {
-        /* XXX: should adjust the result */
         /* Update the floating-point enabled exception summary */
         env->fpscr |= FP_FEX;
         /* We must update the target FPR before raising the exception */
@@ -363,7 +362,6 @@ static inline void float_underflow_excp(CPUPPCState *env)
     /* Update the floating-point exception summary */
     env->fpscr |= FP_FX;
     if (env->fpscr & FP_UE) {
-        /* XXX: should adjust the result */
         /* Update the floating-point enabled exception summary */
         env->fpscr |= FP_FEX;
         /* We must update the target FPR before raising the exception */
-- 
2.31.1
Re: [PATCH 2/2] target/ppc: Bugfix FP when OE/UE are set
Posted by Richard Henderson 1 month, 3 weeks ago
On 8/5/22 07:15, Lucas Mateus Castro(alqotel) wrote:
> From: "Lucas Mateus Castro (alqotel)" <lucas.araujo@eldorado.org.br>
> 
> When an overflow exception occurs and OE is set the intermediate result
> should be adjusted (by subtracting from the exponent) to avoid rounding
> to inf. The same applies to an underflow exceptionion and UE (but adding
> to the exponent). To do this set the fp_status.rebias_overflow when OE
> is set and fp_status.rebias_underflow when UE is set as the FPU will
> recalculate in case of a overflow/underflow if the according rebias* is
> set.
> 
> Signed-off-by: Lucas Mateus Castro (alqotel) <lucas.araujo@eldorado.org.br>
> ---
>   target/ppc/cpu.c        | 2 ++
>   target/ppc/fpu_helper.c | 2 --
>   2 files changed, 2 insertions(+), 2 deletions(-)
> 
> diff --git a/target/ppc/cpu.c b/target/ppc/cpu.c
> index 401b6f9e63..0ebac04bc4 100644
> --- a/target/ppc/cpu.c
> +++ b/target/ppc/cpu.c
> @@ -120,6 +120,8 @@ void ppc_store_fpscr(CPUPPCState *env, target_ulong val)
>           val |= FP_FEX;
>       }
>       env->fpscr = val;
> +    env->fp_status.rebias_overflow  = (FP_OE & env->fpscr) ? true : false;
> +    env->fp_status.rebias_underflow = (FP_UE & env->fpscr) ? true : false;

No point in the ?: operator.

Otherwise,
Reviewed-by: Richard Henderson <richard.henderson@linaro.org>


r~

>       if (tcg_enabled()) {
>           fpscr_set_rounding_mode(env);
>       }
> diff --git a/target/ppc/fpu_helper.c b/target/ppc/fpu_helper.c
> index 134804628b..c17575de5d 100644
> --- a/target/ppc/fpu_helper.c
> +++ b/target/ppc/fpu_helper.c
> @@ -344,7 +344,6 @@ static inline int float_overflow_excp(CPUPPCState *env)
>   
>       bool overflow_enabled = !!(env->fpscr & FP_OE);
>       if (overflow_enabled) {
> -        /* XXX: should adjust the result */
>           /* Update the floating-point enabled exception summary */
>           env->fpscr |= FP_FEX;
>           /* We must update the target FPR before raising the exception */
> @@ -363,7 +362,6 @@ static inline void float_underflow_excp(CPUPPCState *env)
>       /* Update the floating-point exception summary */
>       env->fpscr |= FP_FX;
>       if (env->fpscr & FP_UE) {
> -        /* XXX: should adjust the result */
>           /* Update the floating-point enabled exception summary */
>           env->fpscr |= FP_FEX;
>           /* We must update the target FPR before raising the exception */
Re: [PATCH 2/2] target/ppc: Bugfix FP when OE/UE are set
Posted by Daniel Henrique Barboza 1 month, 3 weeks ago

On 8/5/22 14:17, Richard Henderson wrote:
> On 8/5/22 07:15, Lucas Mateus Castro(alqotel) wrote:
>> From: "Lucas Mateus Castro (alqotel)" <lucas.araujo@eldorado.org.br>
>>
>> When an overflow exception occurs and OE is set the intermediate result
>> should be adjusted (by subtracting from the exponent) to avoid rounding
>> to inf. The same applies to an underflow exceptionion and UE (but adding
>> to the exponent). To do this set the fp_status.rebias_overflow when OE
>> is set and fp_status.rebias_underflow when UE is set as the FPU will
>> recalculate in case of a overflow/underflow if the according rebias* is
>> set.
>>
>> Signed-off-by: Lucas Mateus Castro (alqotel) <lucas.araujo@eldorado.org.br>
>> ---
>>   target/ppc/cpu.c        | 2 ++
>>   target/ppc/fpu_helper.c | 2 --
>>   2 files changed, 2 insertions(+), 2 deletions(-)
>>
>> diff --git a/target/ppc/cpu.c b/target/ppc/cpu.c
>> index 401b6f9e63..0ebac04bc4 100644
>> --- a/target/ppc/cpu.c
>> +++ b/target/ppc/cpu.c
>> @@ -120,6 +120,8 @@ void ppc_store_fpscr(CPUPPCState *env, target_ulong val)
>>           val |= FP_FEX;
>>       }
>>       env->fpscr = val;
>> +    env->fp_status.rebias_overflow  = (FP_OE & env->fpscr) ? true : false;
>> +    env->fp_status.rebias_underflow = (FP_UE & env->fpscr) ? true : false;
> 
> No point in the ?: operator.
> 
> Otherwise,
> Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
> 

Amended in the tree. No need to re-send.


diff --git a/target/ppc/cpu.c b/target/ppc/cpu.c
index 0ebac04bc4..947a4bfe1f 100644
--- a/target/ppc/cpu.c
+++ b/target/ppc/cpu.c
@@ -120,8 +120,8 @@ void ppc_store_fpscr(CPUPPCState *env, target_ulong val)
          val |= FP_FEX;
      }
      env->fpscr = val;
-    env->fp_status.rebias_overflow  = (FP_OE & env->fpscr) ? true : false;
-    env->fp_status.rebias_underflow = (FP_UE & env->fpscr) ? true : false;
+    env->fp_status.rebias_overflow  = FP_OE & env->fpscr;
+    env->fp_status.rebias_underflow = FP_UE & env->fpscr;
      if (tcg_enabled()) {
          fpscr_set_rounding_mode(env);
      }


Thanks,


Daniel

> 
> r~
> 
>>       if (tcg_enabled()) {
>>           fpscr_set_rounding_mode(env);
>>       }
>> diff --git a/target/ppc/fpu_helper.c b/target/ppc/fpu_helper.c
>> index 134804628b..c17575de5d 100644
>> --- a/target/ppc/fpu_helper.c
>> +++ b/target/ppc/fpu_helper.c
>> @@ -344,7 +344,6 @@ static inline int float_overflow_excp(CPUPPCState *env)
>>       bool overflow_enabled = !!(env->fpscr & FP_OE);
>>       if (overflow_enabled) {
>> -        /* XXX: should adjust the result */
>>           /* Update the floating-point enabled exception summary */
>>           env->fpscr |= FP_FEX;
>>           /* We must update the target FPR before raising the exception */
>> @@ -363,7 +362,6 @@ static inline void float_underflow_excp(CPUPPCState *env)
>>       /* Update the floating-point exception summary */
>>       env->fpscr |= FP_FX;
>>       if (env->fpscr & FP_UE) {
>> -        /* XXX: should adjust the result */
>>           /* Update the floating-point enabled exception summary */
>>           env->fpscr |= FP_FEX;
>>           /* We must update the target FPR before raising the exception */
>