| Message ID | 1290538431-13170-8-git-send-email-peter.maydell@linaro.org |
|---|---|
| State | New |
| Headers | show |
On Tue, Nov 23, 2010 at 06:53:46PM +0000, Peter Maydell wrote: > The ARM architecture mandates that converting a NaN value to > integer gives zero (if Invalid Operation FP exceptions are > not being trapped). This isn't the behaviour of the SoftFloat > library, so NaNs must be special-cased. > > +/* Helper routines to identify NaNs. Note that softfloat's > + * floatxx_is_nan() actually only returns true for quiet NaNs. > + * A NaN has an exponent field all 1s and a fraction field > + * anything except all zeros. Conveniently we can detect this > + * by masking out the sign bit and doing an unsigned comparison. > + */ > +static int float32_is_any_nan(float32 x) > +{ > + return ((float32_val(x) & ~(1 << 31)) > 0x7f800000UL); > +} > + > +static int float64_is_any_nan(float64 x) > +{ > + return ((float64_val(x) & ~(1ULL << 63)) > 0x7ff0000000000000ULL); > +} Why not just use: static int float32_is_any_nan(float32 x) { return float32_is_nan(x) || float32_is_signaling_nan(x); } and likewise for the 64-bit case? -Nathan
On 29 November 2010 16:38, Nathan Froyd <froydnj@codesourcery.com> wrote: >> +static int float32_is_any_nan(float32 x) >> +{ >> + return ((float32_val(x) & ~(1 << 31)) > 0x7f800000UL); >> +} >> + >> +static int float64_is_any_nan(float64 x) >> +{ >> + return ((float64_val(x) & ~(1ULL << 63)) > 0x7ff0000000000000ULL); >> +} > > Why not just use: > > static int float32_is_any_nan(float32 x) > { > return float32_is_nan(x) || float32_is_signaling_nan(x); > } > > and likewise for the 64-bit case? That was what my first-pass patches did, but I rewrote them this way because it seemed more straightforward to just test for "is this a NaN" rather than calling two other functions which each test for "is this some subset of NaN space". I suppose you could argue that softfloat ought to have _is_nan() [with the semantics you'd expect from the function name, not the ones it currently has!], _is_signalling_nan() and _is_quiet_nan() functions built in, but it doesn't... -- PMM
On Mon, Nov 29, 2010 at 04:49:24PM +0000, Peter Maydell wrote: > On 29 November 2010 16:38, Nathan Froyd <froydnj@codesourcery.com> wrote: > > Why not just use: > > > > static int float32_is_any_nan(float32 x) > > { > > return float32_is_nan(x) || float32_is_signaling_nan(x); > > } > > > > and likewise for the 64-bit case? > > That was what my first-pass patches did, but I > rewrote them this way because it seemed more > straightforward to just test for "is this a NaN" rather > than calling two other functions which each test for > "is this some subset of NaN space". > > I suppose you could argue that softfloat ought to > have _is_nan() [with the semantics you'd expect > from the function name, not the ones it currently has!], > _is_signalling_nan() and _is_quiet_nan() functions > built in, but it doesn't... I agree that the functions are poorly named. I think it'd be better to leave the bit-twiddling to the softfloat bits, though. There's precedent for the more verbose approach in other backends, too. -Nathan
diff --git a/target-arm/helper.c b/target-arm/helper.c index 996d40d..72ba314 100644 --- a/target-arm/helper.c +++ b/target-arm/helper.c @@ -2445,43 +2445,84 @@ float64 VFP_HELPER(sito, d)(float32 x, CPUState *env) } /* Float to integer conversion. */ + +/* Helper routines to identify NaNs. Note that softfloat's + * floatxx_is_nan() actually only returns true for quiet NaNs. + * A NaN has an exponent field all 1s and a fraction field + * anything except all zeros. Conveniently we can detect this + * by masking out the sign bit and doing an unsigned comparison. + */ +static int float32_is_any_nan(float32 x) +{ + return ((float32_val(x) & ~(1 << 31)) > 0x7f800000UL); +} + +static int float64_is_any_nan(float64 x) +{ + return ((float64_val(x) & ~(1ULL << 63)) > 0x7ff0000000000000ULL); +} + float32 VFP_HELPER(toui, s)(float32 x, CPUState *env) { + if (float32_is_any_nan(x)) { + return float32_zero; + } return vfp_itos(float32_to_uint32(x, &env->vfp.fp_status)); } float32 VFP_HELPER(toui, d)(float64 x, CPUState *env) { + if (float64_is_any_nan(x)) { + return float32_zero; + } return vfp_itos(float64_to_uint32(x, &env->vfp.fp_status)); } float32 VFP_HELPER(tosi, s)(float32 x, CPUState *env) { + if (float32_is_any_nan(x)) { + return float32_zero; + } return vfp_itos(float32_to_int32(x, &env->vfp.fp_status)); } float32 VFP_HELPER(tosi, d)(float64 x, CPUState *env) { + if (float64_is_any_nan(x)) { + return float32_zero; + } return vfp_itos(float64_to_int32(x, &env->vfp.fp_status)); } float32 VFP_HELPER(touiz, s)(float32 x, CPUState *env) { + if (float32_is_any_nan(x)) { + return float32_zero; + } return vfp_itos(float32_to_uint32_round_to_zero(x, &env->vfp.fp_status)); } float32 VFP_HELPER(touiz, d)(float64 x, CPUState *env) { + if (float64_is_any_nan(x)) { + return float32_zero; + } return vfp_itos(float64_to_uint32_round_to_zero(x, &env->vfp.fp_status)); } float32 VFP_HELPER(tosiz, s)(float32 x, CPUState *env) { + if (float32_is_any_nan(x)) { + return float32_zero; + } return vfp_itos(float32_to_int32_round_to_zero(x, &env->vfp.fp_status)); } float32 VFP_HELPER(tosiz, d)(float64 x, CPUState *env) { + if (float64_is_any_nan(x)) { + return float32_zero; + } return vfp_itos(float64_to_int32_round_to_zero(x, &env->vfp.fp_status)); } @@ -2508,6 +2549,9 @@ ftype VFP_HELPER(name##to, p)(ftype x, uint32_t shift, CPUState *env) \ ftype VFP_HELPER(to##name, p)(ftype x, uint32_t shift, CPUState *env) \ { \ ftype tmp; \ + if (ftype##_is_any_nan(x)) { \ + return ftype##_zero; \ + } \ tmp = ftype##_scalbn(x, shift, &env->vfp.fp_status); \ return vfp_ito##p((itype)ftype##_to_##sign##int32_round_to_zero(tmp, \ &env->vfp.fp_status)); \
The ARM architecture mandates that converting a NaN value to integer gives zero (if Invalid Operation FP exceptions are not being trapped). This isn't the behaviour of the SoftFloat library, so NaNs must be special-cased. Signed-off-by: Peter Maydell <peter.maydell@linaro.org> --- target-arm/helper.c | 44 ++++++++++++++++++++++++++++++++++++++++++++ 1 files changed, 44 insertions(+), 0 deletions(-)