This is the mail archive of the
libc-alpha@sourceware.org
mailing list for the glibc project.
soft-fp: Support rsigned == 2 in _FP_TO_INT
- From: "Joseph S. Myers" <joseph at codesourcery dot com>
- To: <libc-alpha at sourceware dot org>
- Date: Tue, 23 Sep 2014 20:41:20 +0000
- Subject: soft-fp: Support rsigned == 2 in _FP_TO_INT
- Authentication-results: sourceware.org; auth=none
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). (This patch is relative to a tree with
<https://sourceware.org/ml/libc-alpha/2014-09/msg00411.html>,
<https://sourceware.org/ml/libc-alpha/2014-09/msg00442.html>,
<https://sourceware.org/ml/libc-alpha/2014-09/msg00461.html>,
<https://sourceware.org/ml/libc-alpha/2014-09/msg00463.html>,
<https://sourceware.org/ml/libc-alpha/2014-09/msg00464.html> and
<https://sourceware.org/ml/libc-alpha/2014-09/msg00488.html> applied;
there are actual dependencies on at least the fourth and fifth of
those patches.)
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.
2014-09-23 Joseph Myers <joseph@codesourcery.com>
* soft-fp/op-common.h (_FP_TO_INT): Handle rsigned == 2.
diff --git a/soft-fp/op-common.h b/soft-fp/op-common.h
index 3deb9b1..cab6fba 100644
--- a/soft-fp/op-common.h
+++ b/soft-fp/op-common.h
@@ -1390,6 +1390,8 @@
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. */
@@ -1411,10 +1413,28 @@
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) \
@@ -1461,6 +1481,7 @@
} \
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) \
{ \
@@ -1469,17 +1490,27 @@
} \
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)
--
Joseph S. Myers
joseph@codesourcery.com