soft-fp: Support conditional zero-initialization in declarations.

In the Linux kernel, some architectures have a single function that
uses different kinds of unpacking and packing depending on the
instruction being emulated, meaning it is not readily visible to the
compiler that variables from _FP_DECL and _FP_FRAC_DECL_* macros are
only used in cases where they were initialized.  The existing copy of
soft-fp in the Linux kernel uses zero-initialization to avoid warnings
in this case, so while frowned upon as a warning suppression mechanism
in code built for glibc it seems appropriate to have such
zero-initialization conditional on __KERNEL__.  This patch duly adds
it, via a macro _FP_ZERO_INIT that expands to empty for non-kernel
compilations.

Tested for powerpc-nofpu that installed stripped shared libraries are
unchanged by this patch.

	* soft-fp/soft-fp.h (_FP_ZERO_INIT): New macro.  Define depending
	on [__KERNEL__].
	* soft-fp/op-1.h (_FP_FRAC_DECL_1): Use _FP_ZERO_INIT.
	* soft-fp/op-2.h (_FP_FRAC_DECL_2): Likewise.
	* soft-fp/op-common.h (_FP_DECL): Likewise.

5 files changed, 26 insertions, 6 deletions

diff --git a/ChangeLog b/ChangeLog
index 7f2e14bcd5..a200bcef96 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,11 @@
+2015-03-07  Joseph Myers  <joseph@codesourcery.com>
+
+	* soft-fp/soft-fp.h (_FP_ZERO_INIT): New macro.  Define depending
+	on [__KERNEL__].
+	* soft-fp/op-1.h (_FP_FRAC_DECL_1): Use _FP_ZERO_INIT.
+	* soft-fp/op-2.h (_FP_FRAC_DECL_2): Likewise.
+	* soft-fp/op-common.h (_FP_DECL): Likewise.
+
 2015-03-06  H.J. Lu  <hongjiu.lu@intel.com>
 
 	* elf/ifuncdep2.c (global): Replace
diff --git a/soft-fp/op-1.h b/soft-fp/op-1.h
index 34c84d01c2..bc9e33bf49 100644
--- a/soft-fp/op-1.h
+++ b/soft-fp/op-1.h
@@ -30,7 +30,7 @@
    License along with the GNU C Library; if not, see
    <http://www.gnu.org/licenses/>.  */
 
-#define _FP_FRAC_DECL_1(X)	_FP_W_TYPE X##_f
+#define _FP_FRAC_DECL_1(X)	_FP_W_TYPE X##_f _FP_ZERO_INIT
 #define _FP_FRAC_COPY_1(D, S)	(D##_f = S##_f)
 #define _FP_FRAC_SET_1(X, I)	(X##_f = I)
 #define _FP_FRAC_HIGH_1(X)	(X##_f)
diff --git a/soft-fp/op-2.h b/soft-fp/op-2.h
index 94a1c71542..26bdfc093d 100644
--- a/soft-fp/op-2.h
+++ b/soft-fp/op-2.h
@@ -30,7 +30,8 @@
    License along with the GNU C Library; if not, see
    <http://www.gnu.org/licenses/>.  */
 
-#define _FP_FRAC_DECL_2(X)	_FP_W_TYPE X##_f0, X##_f1
+#define _FP_FRAC_DECL_2(X)				\
+  _FP_W_TYPE X##_f0 _FP_ZERO_INIT, X##_f1 _FP_ZERO_INIT
 #define _FP_FRAC_COPY_2(D, S)	(D##_f0 = S##_f0, D##_f1 = S##_f1)
 #define _FP_FRAC_SET_2(X, I)	__FP_FRAC_SET_2 (X, I)
 #define _FP_FRAC_HIGH_2(X)	(X##_f1)
diff --git a/soft-fp/op-common.h b/soft-fp/op-common.h
index 14fd6cdc96..ee4147602f 100644
--- a/soft-fp/op-common.h
+++ b/soft-fp/op-common.h
@@ -29,10 +29,10 @@
    License along with the GNU C Library; if not, see
    <http://www.gnu.org/licenses/>.  */
 
-#define _FP_DECL(wc, X)				\
-  _FP_I_TYPE X##_c __attribute__ ((unused));	\
-  _FP_I_TYPE X##_s __attribute__ ((unused));	\
-  _FP_I_TYPE X##_e __attribute__ ((unused));	\
+#define _FP_DECL(wc, X)						\
+  _FP_I_TYPE X##_c __attribute__ ((unused)) _FP_ZERO_INIT;	\
+  _FP_I_TYPE X##_s __attribute__ ((unused)) _FP_ZERO_INIT;	\
+  _FP_I_TYPE X##_e __attribute__ ((unused)) _FP_ZERO_INIT;	\
   _FP_FRAC_DECL_##wc (X)
 
 /* Test whether the qNaN bit denotes a signaling NaN.  */
diff --git a/soft-fp/soft-fp.h b/soft-fp/soft-fp.h
index 1eafcb433d..f93a94182b 100644
--- a/soft-fp/soft-fp.h
+++ b/soft-fp/soft-fp.h
@@ -51,6 +51,17 @@
 # endif
 #endif
 
+/* In the Linux kernel, some architectures have a single function that
+   uses different kinds of unpacking and packing depending on the
+   instruction being emulated, meaning it is not readily visible to
+   the compiler that variables from _FP_DECL and _FP_FRAC_DECL_*
+   macros are only used in cases where they were initialized.  */
+#ifdef __KERNEL__
+# define _FP_ZERO_INIT		= 0
+#else
+# define _FP_ZERO_INIT
+#endif
+
 #define _FP_WORKBITS		3
 #define _FP_WORK_LSB		((_FP_W_TYPE) 1 << 3)
 #define _FP_WORK_ROUND		((_FP_W_TYPE) 1 << 2)