Fix soft-fp fma for -Wuninitialized [committed]

[Joseph Myers <joseph at codesourcery dot com>]

The soft-fp implementations of fma produce -Wuninitialized warnings
because, in the cases where the result is not a nonzero finite value,
the soft-fp does not set the exponent of the result since the (cooked)
packing will do so, but the compiler does not then see that the
exponent is always set in packing before it's used if it wasn't set
earlier.  This patch uses DIAG_* macros to suppress those warnings.

Tested for mips64.  (In fact this allows the mips64 build to complete
with the -Wno-uninitialized removed from math/Makefile, but more
cleanups are still needed in the ldbl-128ibm code for uninitialized
warnings there.)  Committed.

2015-05-22  Joseph Myers  <joseph@codesourcery.com>

	* soft-fp/fmadf4.c: Include <libc-internal.h>.
	(__fma): Ignore uninitialized warnings around packing.
	* soft-fp/fmasf4.c: Include <libc-internal.h>.
	(__fmaf): Ignore uninitialized warnings around packing.
	* soft-fp/fmatf4.c: Include <libc-internal.h>.
	(__fmal): Ignore uninitialized warnings around packing.

diff --git a/soft-fp/fmadf4.c b/soft-fp/fmadf4.c
index 1a720ba..da6749d 100644
--- a/soft-fp/fmadf4.c
+++ b/soft-fp/fmadf4.c
@@ -25,6 +25,7 @@
    License along with the GNU C Library; if not, see
    <http://www.gnu.org/licenses/>.  */
 
+#include <libc-internal.h>
 #include <math.h>
 #include "soft-fp.h"
 #include "double.h"
@@ -44,7 +45,18 @@ __fma (double a, double b, double c)
   FP_UNPACK_D (B, b);
   FP_UNPACK_D (C, c);
   FP_FMA_D (R, A, B, C);
+  /* R_e is not set in cases where it is not used in packing, but the
+     compiler does not see that it is set in all cases where it is
+     used, resulting in warnings that it may be used
+     uninitialized.  */
+  DIAG_PUSH_NEEDS_COMMENT;
+#if __GNUC_PREREQ (4, 7)
+  DIAG_IGNORE_NEEDS_COMMENT (4.9, "-Wmaybe-uninitialized");
+#else
+  DIAG_IGNORE_NEEDS_COMMENT (4.9, "-Wuninitialized");
+#endif
   FP_PACK_D (r, R);
+  DIAG_POP_NEEDS_COMMENT;
   FP_HANDLE_EXCEPTIONS;
 
   return r;
diff --git a/soft-fp/fmasf4.c b/soft-fp/fmasf4.c
index 03855a3..b770a07 100644
--- a/soft-fp/fmasf4.c
+++ b/soft-fp/fmasf4.c
@@ -25,6 +25,7 @@
    License along with the GNU C Library; if not, see
    <http://www.gnu.org/licenses/>.  */
 
+#include <libc-internal.h>
 #include <math.h>
 #include "soft-fp.h"
 #include "single.h"
@@ -44,7 +45,18 @@ __fmaf (float a, float b, float c)
   FP_UNPACK_S (B, b);
   FP_UNPACK_S (C, c);
   FP_FMA_S (R, A, B, C);
+  /* R_e is not set in cases where it is not used in packing, but the
+     compiler does not see that it is set in all cases where it is
+     used, resulting in warnings that it may be used
+     uninitialized.  */
+  DIAG_PUSH_NEEDS_COMMENT;
+#if __GNUC_PREREQ (4, 7)
+  DIAG_IGNORE_NEEDS_COMMENT (4.9, "-Wmaybe-uninitialized");
+#else
+  DIAG_IGNORE_NEEDS_COMMENT (4.9, "-Wuninitialized");
+#endif
   FP_PACK_S (r, R);
+  DIAG_POP_NEEDS_COMMENT;
   FP_HANDLE_EXCEPTIONS;
 
   return r;
diff --git a/soft-fp/fmatf4.c b/soft-fp/fmatf4.c
index 16fd74c..880961c 100644
--- a/soft-fp/fmatf4.c
+++ b/soft-fp/fmatf4.c
@@ -25,6 +25,7 @@
    License along with the GNU C Library; if not, see
    <http://www.gnu.org/licenses/>.  */
 
+#include <libc-internal.h>
 #include <math.h>
 #include "soft-fp.h"
 #include "quad.h"
@@ -44,7 +45,18 @@ __fmal (long double a, long double b, long double c)
   FP_UNPACK_Q (B, b);
   FP_UNPACK_Q (C, c);
   FP_FMA_Q (R, A, B, C);
+  /* R_e is not set in cases where it is not used in packing, but the
+     compiler does not see that it is set in all cases where it is
+     used, resulting in warnings that it may be used
+     uninitialized.  */
+  DIAG_PUSH_NEEDS_COMMENT;
+#if __GNUC_PREREQ (4, 7)
+  DIAG_IGNORE_NEEDS_COMMENT (4.9, "-Wmaybe-uninitialized");
+#else
+  DIAG_IGNORE_NEEDS_COMMENT (4.9, "-Wuninitialized");
+#endif
   FP_PACK_Q (r, R);
+  DIAG_POP_NEEDS_COMMENT;
   FP_HANDLE_EXCEPTIONS;
 
   return r;

-- 
Joseph S. Myers
joseph@codesourcery.com