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soft-fp: Refine FP_EX_DENORM handling for comparisons.

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In <https://sourceware.org/ml/libc-alpha/2014-09/msg00488.html>, I
noted that comparisons in soft-fp did not set FP_EX_DENORM unless
denormal operands were flushed to zero.

This patch fixes soft-fp to check for denormal operands for
comparisons and set that exception whenever FP_EX_DENORM is not zero.
In particular, for the one architecture for which the Linux kernel
defines FP_EX_DENORM (alpha), this corresponds to the existing logic
for comparisons and so allows that logic to be replaced by a simple
call to FP_CMP_D when soft-fp is updated in the kernel.

Tested for powerpc (e500) that installed stripped shared libraries are
unchanged by this patch.

	* soft-fp/op-common.h (_FP_CMP_CHECK_DENORM): New macro.
	(_FP_CMP_CHECK_FLUSH_ZERO): Likewise.
	(_FP_CMP): Use_FP_CMP_CHECK_DENORM and _FP_CMP_CHECK_FLUSH_ZERO.
	(_FP_CMP_EQ): Likewise.
	(_FP_CMP_UNORD): Use _FP_CMP_CHECK_DENORM.
This commit is contained in:
Joseph Myers 2015-02-06 15:41:49 +00:00
parent 639e42eb90
commit 61f006c12d
2 changed files with 51 additions and 4 deletions
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6
ChangeLog
View file

@ -1,5 +1,11 @@
2015-02-06 Joseph Myers <joseph@codesourcery.com>
* soft-fp/op-common.h (_FP_CMP_CHECK_DENORM): New macro.
(_FP_CMP_CHECK_FLUSH_ZERO): Likewise.
(_FP_CMP): Use_FP_CMP_CHECK_DENORM and _FP_CMP_CHECK_FLUSH_ZERO.
(_FP_CMP_EQ): Likewise.
(_FP_CMP_UNORD): Use _FP_CMP_CHECK_DENORM.
* soft-fp/op-common.h (FP_EXTEND): Rename to _FP_EXTEND_CNAN with
extra argument CHECK_NAN. Redefine as wrapper around
_FP_EXTEND_CNAN.

49
soft-fp/op-common.h
View file

@ -1251,6 +1251,46 @@
} \
while (0)
/* Helper for comparisons. If denormal operands would raise an
exception, check for them, and flush to zero as appropriate
(otherwise, we need only check and flush to zero if it might affect
the result, which is done later with _FP_CMP_CHECK_FLUSH_ZERO). */
#define _FP_CMP_CHECK_DENORM(fs, wc, X, Y) \
do \
{ \
if (FP_EX_DENORM != 0) \
{ \
/* We must ensure the correct exceptions are raised for \
denormal operands, even though this may not affect the \
result of the comparison. */ \
if (FP_DENORM_ZERO) \
{ \
_FP_CHECK_FLUSH_ZERO (fs, wc, X); \
_FP_CHECK_FLUSH_ZERO (fs, wc, Y); \
} \
else \
{ \
if ((X##_e == 0 && !_FP_FRAC_ZEROP_##wc (X)) \
|| (Y##_e == 0 && !_FP_FRAC_ZEROP_##wc (Y))) \
FP_SET_EXCEPTION (FP_EX_DENORM); \
} \
} \
} \
while (0)
/* Helper for comparisons. Check for flushing denormals for zero if
we didn't need to check earlier for any denormal operands. */
#define _FP_CMP_CHECK_FLUSH_ZERO(fs, wc, X, Y) \
do \
{ \
if (FP_EX_DENORM == 0) \
{ \
_FP_CHECK_FLUSH_ZERO (fs, wc, X); \
_FP_CHECK_FLUSH_ZERO (fs, wc, Y); \
} \
} \
while (0)
/* Main differential comparison routine. The inputs should be raw not
cooked. The return is -1, 0, 1 for normal values, UN
otherwise. */
@ -1258,6 +1298,7 @@
#define _FP_CMP(fs, wc, ret, X, Y, un, ex) \
do \
{ \
_FP_CMP_CHECK_DENORM (fs, wc, X, Y); \
/* NANs are unordered. */ \
if ((X##_e == _FP_EXPMAX_##fs && !_FP_FRAC_ZEROP_##wc (X)) \
|| (Y##_e == _FP_EXPMAX_##fs && !_FP_FRAC_ZEROP_##wc (Y))) \
@ -1270,8 +1311,7 @@
int _FP_CMP_is_zero_x; \
int _FP_CMP_is_zero_y; \
\
_FP_CHECK_FLUSH_ZERO (fs, wc, X); \
_FP_CHECK_FLUSH_ZERO (fs, wc, Y); \
_FP_CMP_CHECK_FLUSH_ZERO (fs, wc, X, Y); \
\
_FP_CMP_is_zero_x \
= (!X##_e && _FP_FRAC_ZEROP_##wc (X)) ? 1 : 0; \
@ -1306,6 +1346,7 @@
#define _FP_CMP_EQ(fs, wc, ret, X, Y, ex) \
do \
{ \
_FP_CMP_CHECK_DENORM (fs, wc, X, Y); \
/* NANs are unordered. */ \
if ((X##_e == _FP_EXPMAX_##fs && !_FP_FRAC_ZEROP_##wc (X)) \
|| (Y##_e == _FP_EXPMAX_##fs && !_FP_FRAC_ZEROP_##wc (Y))) \
@ -1315,8 +1356,7 @@
} \
else \
{ \
_FP_CHECK_FLUSH_ZERO (fs, wc, X); \
_FP_CHECK_FLUSH_ZERO (fs, wc, Y); \
_FP_CMP_CHECK_FLUSH_ZERO (fs, wc, X, Y); \
\
(ret) = !(X##_e == Y##_e \
&& _FP_FRAC_EQ_##wc (X, Y) \
@ -1331,6 +1371,7 @@
#define _FP_CMP_UNORD(fs, wc, ret, X, Y, ex) \
do \
{ \
_FP_CMP_CHECK_DENORM (fs, wc, X, Y); \
(ret) = ((X##_e == _FP_EXPMAX_##fs && !_FP_FRAC_ZEROP_##wc (X)) \
|| (Y##_e == _FP_EXPMAX_##fs && !_FP_FRAC_ZEROP_##wc (Y))); \
if (ret) \