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Re: [PATCH] soft-fp handling of underflow
From: "Joseph S. Myers" <joseph@codesourcery.com>
Date: Wed, 30 May 2012 09:45:16 +0000 (UTC)
> This patch is OK with an appropriate ChangeLog entry (and 2012 added to
> the copyright dates in op-common.h; we don't yet use ranges of years in
> the copyright notices in soft-fp because GCC's README doesn't yet have a
> notice about the meaning of such ranges).
Done, as below, thanks for reviewing Joseph.
Can you please give some feedback about the FP_EX_DENORM issue on
powerpc? I can't see it being right to generate underflow just
because an input operand is a subnormal. It can be just a "tiny"
one, and in any event underflow is a property of the result we
calculate not of the input operands.
Thanks again.
--------------------
Fix underflow generation in soft-fp.
* soft-fp/soft-fp.h (FP_CUR_EXCEPTIONS): Define.
(FP_TRAPPING_EXCEPTIONS): Provide default implementation.
* sysdeps/sparc/sparc32/soft-fp/sfp-machine.h
(FP_TRAPPING_EXCEPTIONS): Define.
* sysdeps/sparc/sparc64/soft-fp/sfp-machine.h
(FP_TRAPPING_EXCEPTIONS): Define.
* soft-fp/op-common.h (_FP_PACK_SEMIRAW): Signal underflow for
subnormals only when inexact has been signalled or underflow
exceptions are enabled.
(_FP_PACK_CANONICAL): Likewise.
---
ChangeLog | 13 +++++++++++++
soft-fp/op-common.h | 13 ++++++++++---
soft-fp/soft-fp.h | 7 +++++++
sysdeps/sparc/sparc32/soft-fp/sfp-machine.h | 3 ++-
sysdeps/sparc/sparc64/soft-fp/sfp-machine.h | 3 ++-
5 files changed, 34 insertions(+), 5 deletions(-)
diff --git a/ChangeLog b/ChangeLog
index 42df8d7..4adb73a 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,16 @@
+2012-05-30 David S. Miller <davem@davemloft.net>
+
+ * soft-fp/soft-fp.h (FP_CUR_EXCEPTIONS): Define.
+ (FP_TRAPPING_EXCEPTIONS): Provide default implementation.
+ * sysdeps/sparc/sparc32/soft-fp/sfp-machine.h
+ (FP_TRAPPING_EXCEPTIONS): Define.
+ * sysdeps/sparc/sparc64/soft-fp/sfp-machine.h
+ (FP_TRAPPING_EXCEPTIONS): Define.
+ * soft-fp/op-common.h (_FP_PACK_SEMIRAW): Signal underflow for
+ subnormals only when inexact has been signalled or underflow
+ exceptions are enabled.
+ (_FP_PACK_CANONICAL): Likewise.
+
2012-05-30 H.J. Lu <hongjiu.lu@intel.com>
[BZ #14183]
diff --git a/soft-fp/op-common.h b/soft-fp/op-common.h
index b70026f..db75af5 100644
--- a/soft-fp/op-common.h
+++ b/soft-fp/op-common.h
@@ -1,5 +1,5 @@
/* Software floating-point emulation. Common operations.
- Copyright (C) 1997,1998,1999,2006,2007 Free Software Foundation, Inc.
+ Copyright (C) 1997,1998,1999,2006,2007,2012 Free Software Foundation, Inc.
This file is part of the GNU C Library.
Contributed by Richard Henderson (rth@cygnus.com),
Jakub Jelinek (jj@ultra.linux.cz),
@@ -146,7 +146,11 @@ do { \
if (!_FP_EXP_NORMAL(fs, wc, X) && !_FP_FRAC_ZEROP_##wc(X)) \
{ \
if (X##_e == 0) \
- FP_SET_EXCEPTION(FP_EX_UNDERFLOW); \
+ { \
+ if ((FP_CUR_EXCEPTIONS & FP_EX_INEXACT) \
+ || (FP_TRAPPING_EXCEPTIONS & FP_EX_UNDERFLOW)) \
+ FP_SET_EXCEPTION(FP_EX_UNDERFLOW); \
+ } \
else \
{ \
if (!_FP_KEEPNANFRACP) \
@@ -226,13 +230,16 @@ do { \
{ \
X##_e = 1; \
_FP_FRAC_SET_##wc(X, _FP_ZEROFRAC_##wc); \
+ FP_SET_EXCEPTION(FP_EX_INEXACT); \
} \
else \
{ \
X##_e = 0; \
_FP_FRAC_SRL_##wc(X, _FP_WORKBITS); \
- FP_SET_EXCEPTION(FP_EX_UNDERFLOW); \
} \
+ if ((FP_CUR_EXCEPTIONS & FP_EX_INEXACT) \
+ || (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 46cb1cf..750c7fe 100644
--- a/soft-fp/soft-fp.h
+++ b/soft-fp/soft-fp.h
@@ -128,6 +128,13 @@
#define FP_CLEAR_EXCEPTIONS \
_fex = 0
+#define FP_CUR_EXCEPTIONS \
+ (_fex)
+
+#ifndef FP_TRAPPING_EXCEPTIONS
+#define FP_TRAPPING_EXCEPTIONS 0
+#endif
+
#define _FP_ROUND_NEAREST(wc, X) \
do { \
if ((_FP_FRAC_LOW_##wc(X) & 15) != _FP_WORK_ROUND) \
diff --git a/sysdeps/sparc/sparc32/soft-fp/sfp-machine.h b/sysdeps/sparc/sparc32/soft-fp/sfp-machine.h
index 4314082..e60f1ca 100644
--- a/sysdeps/sparc/sparc32/soft-fp/sfp-machine.h
+++ b/sysdeps/sparc/sparc32/soft-fp/sfp-machine.h
@@ -1,6 +1,6 @@
/* Machine-dependent software floating-point definitions.
Sparc userland (_Q_*) version.
- Copyright (C) 1997,1998,1999, 2002, 2006 Free Software Foundation, Inc.
+ Copyright (C) 1997,1998,1999,2002,2006,2012 Free Software Foundation, Inc.
This file is part of the GNU C Library.
Contributed by Richard Henderson (rth@cygnus.com),
Jakub Jelinek (jj@ultra.linux.cz) and
@@ -192,6 +192,7 @@ do { \
_FPU_GETCW(_fcw); \
} while (0)
+#define FP_TRAPPING_EXCEPTIONS ((_fcw >> 23) & 0x1f)
#define FP_INHIBIT_RESULTS ((_fcw >> 23) & _fex)
/* Simulate exceptions using double arithmetics. */
diff --git a/sysdeps/sparc/sparc64/soft-fp/sfp-machine.h b/sysdeps/sparc/sparc64/soft-fp/sfp-machine.h
index 36f92d6..9bd4298 100644
--- a/sysdeps/sparc/sparc64/soft-fp/sfp-machine.h
+++ b/sysdeps/sparc/sparc64/soft-fp/sfp-machine.h
@@ -1,6 +1,6 @@
/* Machine-dependent software floating-point definitions.
Sparc64 userland (_Q_* and _Qp_*) version.
- Copyright (C) 1997, 1998, 1999, 2006 Free Software Foundation, Inc.
+ Copyright (C) 1997, 1998, 1999, 2006, 2012 Free Software Foundation, Inc.
This file is part of the GNU C Library.
Contributed by Richard Henderson (rth@cygnus.com),
Jakub Jelinek (jj@ultra.linux.cz) and
@@ -100,6 +100,7 @@ do { \
_FPU_GETCW(_fcw); \
} while (0)
+#define FP_TRAPPING_EXCEPTIONS ((_fcw >> 23) & 0x1f)
#define FP_INHIBIT_RESULTS ((_fcw >> 23) & _fex)
/* Simulate exceptions using double arithmetics. */
--
1.7.10