Re: [RFC PATCH 2/8] fpu/softfloat: use the similiar logic to recognize sNaN and qNaN

[LIU Zhiwei]

On 2020/7/14 3:17, Richard Henderson wrote:

On 7/12/20 4:45 PM, LIU Zhiwei wrote:

Signed-off-by: LIU Zhiwei 
---
  fpu/softfloat-specialize.inc.c | 8 
  1 file changed, 4 insertions(+), 4 deletions(-)

diff --git a/fpu/softfloat-specialize.inc.c b/fpu/softfloat-specialize.inc.c
index 034d18199c..6b778a7830 100644
--- a/fpu/softfloat-specialize.inc.c
+++ b/fpu/softfloat-specialize.inc.c
@@ -292,7 +292,7 @@ bool float32_is_quiet_nan(float32 a_, float_status *status)
  if (snan_bit_is_one(status)) {
  return (((a >> 22) & 0x1FF) == 0x1FE) && (a & 0x003F);
  } else {
-return ((uint32_t)(a << 1) >= 0xFF80);
+return ((a >> 22) & 0x1FF) == 0x1FF;
  }
  #endif
  }

I don't see a reason for this.  The previous was a bug, but this isn't.

It's not a bug,  just a clean up.

As you can see, we have already recognized a quiet nan by

 if (snan_bit_is_one(status)) {
 return (((a >> 22) & 0x1FF) == 0x1FE) && (a & 0x003F);
 }

We need not to give another method to recognize it again.

Zhiwei


r~

Re: [RFC PATCH 2/8] fpu/softfloat: use the similiar logic to recognize sNaN and qNaN

[Richard Henderson]

On 7/12/20 4:45 PM, LIU Zhiwei wrote:
> Signed-off-by: LIU Zhiwei 
> ---
>  fpu/softfloat-specialize.inc.c | 8 
>  1 file changed, 4 insertions(+), 4 deletions(-)
> 
> diff --git a/fpu/softfloat-specialize.inc.c b/fpu/softfloat-specialize.inc.c
> index 034d18199c..6b778a7830 100644
> --- a/fpu/softfloat-specialize.inc.c
> +++ b/fpu/softfloat-specialize.inc.c
> @@ -292,7 +292,7 @@ bool float32_is_quiet_nan(float32 a_, float_status 
> *status)
>  if (snan_bit_is_one(status)) {
>  return (((a >> 22) & 0x1FF) == 0x1FE) && (a & 0x003F);
>  } else {
> -return ((uint32_t)(a << 1) >= 0xFF80);
> +return ((a >> 22) & 0x1FF) == 0x1FF;
>  }
>  #endif
>  }

I don't see a reason for this.  The previous was a bug, but this isn't.


r~

[RFC PATCH 2/8] fpu/softfloat: use the similiar logic to recognize sNaN and qNaN

[LIU Zhiwei]

Signed-off-by: LIU Zhiwei 
---
 fpu/softfloat-specialize.inc.c | 8 
 1 file changed, 4 insertions(+), 4 deletions(-)

diff --git a/fpu/softfloat-specialize.inc.c b/fpu/softfloat-specialize.inc.c
index 034d18199c..6b778a7830 100644
--- a/fpu/softfloat-specialize.inc.c
+++ b/fpu/softfloat-specialize.inc.c
@@ -292,7 +292,7 @@ bool float32_is_quiet_nan(float32 a_, float_status *status)
 if (snan_bit_is_one(status)) {
 return (((a >> 22) & 0x1FF) == 0x1FE) && (a & 0x003F);
 } else {
-return ((uint32_t)(a << 1) >= 0xFF80);
+return ((a >> 22) & 0x1FF) == 0x1FF;
 }
 #endif
 }
@@ -309,7 +309,7 @@ bool float32_is_signaling_nan(float32 a_, float_status 
*status)
 #else
 uint32_t a = float32_val(a_);
 if (snan_bit_is_one(status)) {
-return ((uint32_t)(a << 1) >= 0xFF80);
+return ((a >> 22) & 0x1FF) == 0x1FF;
 } else {
 return (((a >> 22) & 0x1FF) == 0x1FE) && (a & 0x003F);
 }
@@ -647,7 +647,7 @@ bool float64_is_quiet_nan(float64 a_, float_status *status)
 return (((a >> 51) & 0xFFF) == 0xFFE)
 && (a & 0x0007ULL);
 } else {
-return ((a << 1) >= 0xFFF0ULL);
+return ((a >> 51) & 0xFFF) == 0xFFF;
 }
 #endif
 }
@@ -664,7 +664,7 @@ bool float64_is_signaling_nan(float64 a_, float_status 
*status)
 #else
 uint64_t a = float64_val(a_);
 if (snan_bit_is_one(status)) {
-return ((a << 1) >= 0xFFF0ULL);
+return ((a >> 51) & 0xFFF) == 0xFFF;
 } else {
 return (((a >> 51) & 0xFFF) == 0xFFE)
 && (a & UINT64_C(0x0007));
-- 
2.23.0