[Qemu-devel] [PATCH 0/3] softfloat/arm: fix 'int32 is 32 bits' assumptions

[Peter Maydell]

These patches fix some assumptions that are made by various bits
of code that the softfloat 'int32' and 'uint32' types are exactly
32 bits rather than at least 32 bits. I found these issues as part
of testing Andreas' recent softfloat type fixes patchset. What
I did was to take the first four patches from Andreas' set (the
fixes for type mixups) and then do a test run of my ARM VFP/Neon
tests with the following two sets of typedefs:

/* maximum-width versions */
typedef uint64_t flag;
typedef uint64_t uint8;
typedef int64_t int8;
typedef uint64_t uint16;
typedef int64_t int16;
typedef uint64_t uint32;
typedef int64_t int32;
typedef uint64_t uint64;
typedef int64_t int64;

/* minimum-width versions */
typedef uint8_t flag;
typedef uint8_t uint8;
typedef int8_t int8;
typedef uint16_t uint16;
typedef int16_t int16;
typedef uint32_t uint32;
typedef int32_t int32;
typedef uint64_t uint64;
typedef int64_t int64;

to flush out the two obvious possible problems: code which
assumes the type is larger than it might be, and code which
assumes the type is not as large as it might be. These test
runs revealed a few bugs, which this patchseries fixes.
These are basically all assumptions about the size of int32
in float-to-int or int-to-float code, and represent real rather
than theoretical problems with the switch to int_fast*_t
since on 64 bit hosts int_fast32_t is typically 64 bits.

NB: I think I've fairly solidly exercised the bits of softfloat
that ARM uses, but can't guarantee coverage of anything that's
only used by other targets or target-specific non-ARM code.

Andreas: these sit after your patches 1-4, so it might be
easiest if you just stick them in your patch series; like
your 1-4 they can be applied now as they make sense even without
the type conversion patches.


Peter Maydell (3):
  target-arm/helper.c: Don't assume softfloat int32 is 32 bits only
  softfloat: float*_to_int32_round_to_zero: don't assume int32 is 32 bits
  softfloat: roundAndPackInt{32,64}: Don't assume int32 is 32 bits

 fpu/softfloat.c     |   12 ++++++------
 target-arm/helper.c |    2 +-
 2 files changed, 7 insertions(+), 7 deletions(-)