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authorJoseph Myers <joseph@codesourcery.com>2015-02-06 15:41:49 +0000
committerJoseph Myers <joseph@codesourcery.com>2015-02-06 15:41:49 +0000
commit61f006c12d8ff3a80a95a36fed81c908a2e39650 (patch)
treeb669c8f9c4ef70907f386bf034f5567fcded7ba7 /soft-fp
parent639e42eb901b69d3a4d6414751c60fab0ca25119 (diff)
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soft-fp: Refine FP_EX_DENORM handling for comparisons.
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.
Diffstat (limited to 'soft-fp')
-rw-r--r--soft-fp/op-common.h49
1 files changed, 45 insertions, 4 deletions
diff --git a/soft-fp/op-common.h b/soft-fp/op-common.h
index 98cc721..389ba3f 100644
--- a/soft-fp/op-common.h
+++ b/soft-fp/op-common.h
@@ -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) \