[Qemu-devel] [PATCH 0/4] target/arm: Fix int64_to_float16 double-rounding

[Richard Henderson]

In 88808a022c0, I tried to fix an overflow problem that affected float16
scaling by coverting first to float64 and then rounding after that.  

However, Laurent reported that -0x3ff40000000001 converted to float16
resulted in 0xfbfe instead of the expected 0xfbff.  This is caused by
the inexact conversion to float64.

Rather than build more logic into target/arm to compensate, just add
a function that takes a scaling parameter so that the whole thing is
done all at once with only one rounding.

I don't have a failing test case for the float-to-int paths, but it
seemed best to apply the same solution.


r~


Richard Henderson (4):
  softfloat: Add scaling int-to-float routines
  softfloat: Add scaling float-to-int routines
  target/arm: Use the int-to-float-scale softfloat routines
  target/arm: Use the float-to-int-scale softfloat routines

 include/fpu/softfloat.h | 169 ++++++++----
 fpu/softfloat.c         | 579 +++++++++++++++++++++++++++++++---------
 target/arm/helper.c     | 130 ++++-----
 3 files changed, 628 insertions(+), 250 deletions(-)

-- 
2.17.1