| Message ID | 1388496958-3542-18-git-send-email-peter.maydell@linaro.org |
|---|---|
| State | New |
| Headers | show |
On 12/31/2013 05:35 AM, Peter Maydell wrote: > The VFP fixed point conversion helpers first call float_scalbn and > then convert the result to an integer. This scalbn operation may > set floating point exception flags for: > * overflow & inexact (if it overflows to infinity) > * input denormal squashed to zero > * output denormal squashed to zero > Of these, we only care about the input-denormal flag, since > the output of the whole scale-and-convert operation will be > an integer (so squashed-output-denormal and overflow don't > apply). Suppress the others by saving the pre-scalb exception > flags and only copying across a potential input-denormal flag. > > Signed-off-by: Peter Maydell <peter.maydell@linaro.org> > --- > target-arm/helper.c | 9 +++++++++ > 1 file changed, 9 insertions(+) Reviewed-by: Richard Henderson <rth@twiddle.net> r~
diff --git a/target-arm/helper.c b/target-arm/helper.c index a9b0927..67dc212 100644 --- a/target-arm/helper.c +++ b/target-arm/helper.c @@ -3994,18 +3994,27 @@ float##fsz HELPER(vfp_##name##to##p)(uint##isz##_t x, uint32_t shift, \ return float##fsz##_scalbn(tmp, -(int)shift, fpst); \ } +/* Notice that we want only input-denormal exception flags from the + * scalbn operation: the other possible flags (overflow+inexact if + * we overflow to infinity, output-denormal) aren't correct for the + * complete scale-and-convert operation. + */ #define VFP_CONV_FLOAT_FIX_ROUND(name, p, fsz, isz, itype, round) \ uint##isz##_t HELPER(vfp_to##name##p##round)(float##fsz x, \ uint32_t shift, \ void *fpstp) \ { \ float_status *fpst = fpstp; \ + int old_exc_flags = get_float_exception_flags(fpst); \ float##fsz tmp; \ if (float##fsz##_is_any_nan(x)) { \ float_raise(float_flag_invalid, fpst); \ return 0; \ } \ tmp = float##fsz##_scalbn(x, shift, fpst); \ + old_exc_flags |= get_float_exception_flags(fpst) \ + & float_flag_input_denormal; \ + set_float_exception_flags(old_exc_flags, fpst); \ return float##fsz##_to_##itype##round(tmp, fpst); \ }
The VFP fixed point conversion helpers first call float_scalbn and then convert the result to an integer. This scalbn operation may set floating point exception flags for: * overflow & inexact (if it overflows to infinity) * input denormal squashed to zero * output denormal squashed to zero Of these, we only care about the input-denormal flag, since the output of the whole scale-and-convert operation will be an integer (so squashed-output-denormal and overflow don't apply). Suppress the others by saving the pre-scalb exception flags and only copying across a potential input-denormal flag. Signed-off-by: Peter Maydell <peter.maydell@linaro.org> --- target-arm/helper.c | 9 +++++++++ 1 file changed, 9 insertions(+)