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soft-fp: Support rsigned == 2 in _FP_TO_INT.

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Continuing the addition of soft-fp features in the Linux kernel
version, this patch adds _FP_TO_INT support for rsigned == 2 (reduce
overflowing results modulo 2^rsize to fit in the destination, used for
alpha emulation).

The kernel version is buggy; it can left shift by a negative amount
when right shifting is required in an overflow case (the kernel
version also has other bugs fixed long ago in glibc; at least,
spurious exceptions converting to the most negative integer).  This
version avoids that by handling overflow (other than to 0) for rsigned
== 2 along with the normal non-overflow case, which already properly
determines the direction in which to shift.

Tested for powerpc-nofpu.  Some functions get slightly bigger and some
get slightly smaller, no doubt as a result of the change to where in
the macro "inexact" is raised, but I don't think those changes are
significant.  Also tested for powerpc-nofpu with the relevant __fix*
functions changed to use rsigned == 2 (which is after all just as
valid as rsigned == 1 in IEEE terms), including verifying the results
and exceptions for various cases of conversions.

With these seven patches, the one remaining feature to add for the
soft-fp code to have all the features of the kernel version is
_FP_TO_INT_ROUND.

	* soft-fp/op-common.h (_FP_TO_INT): Handle rsigned == 2.
This commit is contained in:
Joseph Myers 2014-10-09 15:00:37 +00:00
parent ff12c11f45
commit a736ec370a
2 changed files with 40 additions and 7 deletions
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2
ChangeLog
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@ -1,5 +1,7 @@
2014-10-09 Joseph Myers <joseph@codesourcery.com>
* soft-fp/op-common.h (_FP_TO_INT): Handle rsigned == 2.
* soft-fp/soft-fp.h (FP_EX_INVALID_SNAN): New macro.
(FP_EX_INVALID_IMZ): Likewise.
(FP_EX_INVALID_IMZ_FMA): Likewise.

45
soft-fp/op-common.h
View File

@ -1399,6 +1399,8 @@
1: the number is required to be -(2^(rsize-1))..(2^(rsize-1))-1, if not,
NV is set plus the result is either -(2^(rsize-1)) or (2^(rsize-1))-1
depending on the sign in such case.
2: the number is required to be -(2^(rsize-1))..(2^(rsize-1))-1, if not,
NV is set plus the result is reduced modulo 2^rsize.
-1: the number is required to be -(2^(rsize-1))..(2^rsize)-1, if not, NV is
set plus the result is either -(2^(rsize-1)) or (2^(rsize-1))-1
depending on the sign in such case. */
@ -1420,10 +1422,28 @@
else \
FP_SET_EXCEPTION (FP_EX_INEXACT); \
} \
else if (X##_e >= (_FP_EXPMAX_##fs < _FP_EXPBIAS_##fs + rsize \
? _FP_EXPMAX_##fs \
: _FP_EXPBIAS_##fs + rsize - (rsigned > 0 || X##_s)) \
|| (!rsigned && X##_s)) \
else if (rsigned == 2 \
&& (X##_e \
>= ((_FP_EXPMAX_##fs \
< _FP_EXPBIAS_##fs + _FP_FRACBITS_##fs + rsize - 1) \
? _FP_EXPMAX_##fs \
: _FP_EXPBIAS_##fs + _FP_FRACBITS_##fs + rsize - 1))) \
{ \
/* Overflow resulting in 0. */ \
r = 0; \
FP_SET_EXCEPTION (FP_EX_INVALID \
| FP_EX_INVALID_CVI \
| ((FP_EX_INVALID_SNAN \
&& _FP_ISSIGNAN (fs, wc, X)) \
? FP_EX_INVALID_SNAN \
: 0)); \
} \
else if (rsigned != 2 \
&& (X##_e >= (_FP_EXPMAX_##fs < _FP_EXPBIAS_##fs + rsize \
? _FP_EXPMAX_##fs \
: (_FP_EXPBIAS_##fs + rsize \
- (rsigned > 0 || X##_s))) \
|| (!rsigned && X##_s))) \
{ \
/* Overflow or converting to the most negative integer. */ \
if (rsigned) \
@ -1470,6 +1490,7 @@
} \
else \
{ \
int _FP_TO_INT_inexact = 0; \
_FP_FRAC_HIGH_RAW_##fs (X) |= _FP_IMPLBIT_##fs; \
if (X##_e >= _FP_EXPBIAS_##fs + _FP_FRACBITS_##fs - 1) \
{ \
@ -1478,17 +1499,27 @@
} \
else \
{ \
int _FP_TO_INT_inexact; \
_FP_FRAC_SRST_##wc (X, _FP_TO_INT_inexact, \
(_FP_FRACBITS_##fs + _FP_EXPBIAS_##fs - 1 \
- X##_e), \
_FP_FRACBITS_##fs); \
if (_FP_TO_INT_inexact) \
FP_SET_EXCEPTION (FP_EX_INEXACT); \
_FP_FRAC_ASSEMBLE_##wc (r, X, rsize); \
} \
if (rsigned && X##_s) \
r = -r; \
if (rsigned == 2 && X##_e >= _FP_EXPBIAS_##fs + rsize - 1) \
{ \
/* Overflow or converting to the most negative integer. */ \
if (X##_e > _FP_EXPBIAS_##fs + rsize - 1 \
|| !X##_s \
|| r != (((typeof (r)) 1) << (rsize - 1))) \
{ \
_FP_TO_INT_inexact = 0; \
FP_SET_EXCEPTION (FP_EX_INVALID | FP_EX_INVALID_CVI); \
} \
} \
if (_FP_TO_INT_inexact) \
FP_SET_EXCEPTION (FP_EX_INEXACT); \
} \
} \
while (0)