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GNU C Library master sources branch master updated. glibc-2.20-73-g43059f4
- From: jsm28 at sourceware dot org
- To: glibc-cvs at sourceware dot org
- Date: 9 Oct 2014 01:01:40 -0000
- Subject: GNU C Library master sources branch master updated. glibc-2.20-73-g43059f4
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http://sourceware.org/git/gitweb.cgi?p=glibc.git;a=commitdiff;h=43059f42dbd6dd3926c33ee0cbc7583f0c3e84b9
commit 43059f42dbd6dd3926c33ee0cbc7583f0c3e84b9
Author: Joseph Myers <joseph@codesourcery.com>
Date: Thu Oct 9 01:00:41 2014 +0000
soft-fp: Make extensions of subnormals from XFmode to TFmode signal underflow if traps enabled.
This patch fixes a soft-fp corner case I previously noted in
<https://sourceware.org/ml/libc-alpha/2013-10/msg00349.html>: when
trapping on underflow is enabled, extensions of subnormals from XFmode
to TFmode need to signal underflow because the result is tiny (but
exact, so the underflow flag is not raised unless trapping is
enabled).
To avoid any excess initialization or tests for other cases of
floating-point extensions, a new FP_INIT_TRAPPING_EXCEPTIONS is added
that does the initialization required for this particular case (more
than FP_INIT_EXCEPTIONS, less than FP_INIT_ROUNDMODE, in general), and
FP_NO_EXACT_UNDERFLOW is added to stub out FP_TRAPPING_EXCEPTIONS
tests for those cases of extensions where the test would be dead code,
to avoid any uninitialized variable warnings.
As the relevant case only applies in libgcc, not to any use of soft-fp
in glibc, there is no bug report in Bugzilla and no non-default
definitions of FP_INIT_TRAPPING_EXCEPTIONS are added by the patch. A
testcase will be added to GCC as part of an update of soft-fp in
libgcc once this patch is in libc.
Tested for powerpc-nofpu that the disassembly of installed shared
libraries is unchanged by this patch. Bootstrapped GCC with updated
soft-fp with no regressions on x86_64-unknown-linux-gnu and verified
that a test of the relevant case passes where it failed before.
* soft-fp/op-common.h (FP_EXTEND): When a subnormal input produces
a subnormal result, set the underflow exception if trapping on
underflow is enabled.
* soft-fp/soft-fp.h (FP_INIT_TRAPPING_EXCEPTIONS): New macro.
(FP_INIT_EXCEPTIONS): Default to FP_INIT_TRAPPING_EXCEPTIONS.
[FP_NO_EXACT_UNDERFLOW] (FP_TRAPPING_EXCEPTIONS): Undefine and
redefine to 0.
* soft-fp/extenddftf2.c (FP_NO_EXACT_UNDERFLOW): Define.
* soft-fp/extendsfdf2.c (FP_NO_EXACT_UNDERFLOW): Likewise.
* soft-fp/extendsftf2.c (FP_NO_EXACT_UNDERFLOW): Likewise.
* soft-fp/extendxftf2.c (__extendxftf2): Use
FP_INIT_TRAPPING_EXCEPTIONS instead of FP_INIT_ROUNDMODE.
diff --git a/ChangeLog b/ChangeLog
index b5faff4..703934d 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,5 +1,18 @@
2014-10-09 Joseph Myers <joseph@codesourcery.com>
+ * soft-fp/op-common.h (FP_EXTEND): When a subnormal input produces
+ a subnormal result, set the underflow exception if trapping on
+ underflow is enabled.
+ * soft-fp/soft-fp.h (FP_INIT_TRAPPING_EXCEPTIONS): New macro.
+ (FP_INIT_EXCEPTIONS): Default to FP_INIT_TRAPPING_EXCEPTIONS.
+ [FP_NO_EXACT_UNDERFLOW] (FP_TRAPPING_EXCEPTIONS): Undefine and
+ redefine to 0.
+ * soft-fp/extenddftf2.c (FP_NO_EXACT_UNDERFLOW): Define.
+ * soft-fp/extendsfdf2.c (FP_NO_EXACT_UNDERFLOW): Likewise.
+ * soft-fp/extendsftf2.c (FP_NO_EXACT_UNDERFLOW): Likewise.
+ * soft-fp/extendxftf2.c (__extendxftf2): Use
+ FP_INIT_TRAPPING_EXCEPTIONS instead of FP_INIT_ROUNDMODE.
+
* soft-fp/soft-fp.h (FP_CLEAR_EXCEPTIONS): Remove macro.
* sysdeps/sparc/sparc32/soft-fp/q_itoq.c: Define FP_NO_EXCEPTIONS.
(_Q_itoq): Do not use FP_DECL_EX, FP_CLEAR_EXCEPTIONS or
diff --git a/soft-fp/extenddftf2.c b/soft-fp/extenddftf2.c
index 6984b41..1765532 100644
--- a/soft-fp/extenddftf2.c
+++ b/soft-fp/extenddftf2.c
@@ -28,6 +28,7 @@
License along with the GNU C Library; if not, see
<http://www.gnu.org/licenses/>. */
+#define FP_NO_EXACT_UNDERFLOW
#include "soft-fp.h"
#include "double.h"
#include "quad.h"
diff --git a/soft-fp/extendsfdf2.c b/soft-fp/extendsfdf2.c
index a9b6bfb..6224195 100644
--- a/soft-fp/extendsfdf2.c
+++ b/soft-fp/extendsfdf2.c
@@ -28,6 +28,7 @@
License along with the GNU C Library; if not, see
<http://www.gnu.org/licenses/>. */
+#define FP_NO_EXACT_UNDERFLOW
#include "soft-fp.h"
#include "single.h"
#include "double.h"
diff --git a/soft-fp/extendsftf2.c b/soft-fp/extendsftf2.c
index 07fc367..f67d614 100644
--- a/soft-fp/extendsftf2.c
+++ b/soft-fp/extendsftf2.c
@@ -28,6 +28,7 @@
License along with the GNU C Library; if not, see
<http://www.gnu.org/licenses/>. */
+#define FP_NO_EXACT_UNDERFLOW
#include "soft-fp.h"
#include "single.h"
#include "quad.h"
diff --git a/soft-fp/extendxftf2.c b/soft-fp/extendxftf2.c
index 67b9095..a1386a6 100644
--- a/soft-fp/extendxftf2.c
+++ b/soft-fp/extendxftf2.c
@@ -39,7 +39,7 @@ __extendxftf2 (XFtype a)
FP_DECL_Q (R);
TFtype r;
- FP_INIT_ROUNDMODE;
+ FP_INIT_TRAPPING_EXCEPTIONS;
FP_UNPACK_RAW_E (A, a);
#if (2 * _FP_W_TYPE_SIZE) < _FP_FRACBITS_Q
FP_EXTEND (Q, E, 4, 4, R, A);
diff --git a/soft-fp/op-common.h b/soft-fp/op-common.h
index ec0bc42..e3212ec 100644
--- a/soft-fp/op-common.h
+++ b/soft-fp/op-common.h
@@ -1522,6 +1522,8 @@
_FP_FRAC_SLL_##dwc (D, (_FP_FRACBITS_##dfs \
- _FP_FRACBITS_##sfs)); \
D##_e = 0; \
+ if (FP_TRAPPING_EXCEPTIONS & FP_EX_UNDERFLOW) \
+ FP_SET_EXCEPTION (FP_EX_UNDERFLOW); \
} \
else \
{ \
diff --git a/soft-fp/soft-fp.h b/soft-fp/soft-fp.h
index ead9c97..4018b0e 100644
--- a/soft-fp/soft-fp.h
+++ b/soft-fp/soft-fp.h
@@ -108,9 +108,15 @@
#endif
/* Initialize any machine-specific state used in
+ FP_TRAPPING_EXCEPTIONS or FP_HANDLE_EXCEPTIONS. */
+#ifndef FP_INIT_TRAPPING_EXCEPTIONS
+# define FP_INIT_TRAPPING_EXCEPTIONS FP_INIT_ROUNDMODE
+#endif
+
+/* Initialize any machine-specific state used in
FP_HANDLE_EXCEPTIONS. */
#ifndef FP_INIT_EXCEPTIONS
-# define FP_INIT_EXCEPTIONS FP_INIT_ROUNDMODE
+# define FP_INIT_EXCEPTIONS FP_INIT_TRAPPING_EXCEPTIONS
#endif
#ifndef FP_HANDLE_EXCEPTIONS
@@ -162,6 +168,16 @@
#endif
+/* A file using soft-fp may define FP_NO_EXACT_UNDERFLOW before
+ including soft-fp.h to indicate that, although a macro used there
+ could allow for the case of exact underflow requiring the underflow
+ exception to be raised if traps are enabled, for the particular
+ arguments used in that file no exact underflow can occur. */
+#ifdef FP_NO_EXACT_UNDERFLOW
+# undef FP_TRAPPING_EXCEPTIONS
+# define FP_TRAPPING_EXCEPTIONS 0
+#endif
+
#define _FP_ROUND_NEAREST(wc, X) \
do \
{ \
-----------------------------------------------------------------------
Summary of changes:
ChangeLog | 13 +++++++++++++
soft-fp/extenddftf2.c | 1 +
soft-fp/extendsfdf2.c | 1 +
soft-fp/extendsftf2.c | 1 +
soft-fp/extendxftf2.c | 2 +-
soft-fp/op-common.h | 2 ++
soft-fp/soft-fp.h | 18 +++++++++++++++++-
7 files changed, 36 insertions(+), 2 deletions(-)
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