Handle narrowing function sNaN test disabling based on argument format.

Testing narrowing functions for x86_64 with GCC 6 showed up a further
testsuite fix needed: there is no _Float128 sNaN support before GCC 7
on x86_64 / x86, and the existing tests of SNAN_TESTS only checked it
for the return type, not for the argument type.  This patch fixes the
code to check SNAN_TESTS (ARG_FLOAT) as well (in a variable set in
libm-test-driver.c, since libm-test-support.c is compiled only once
for each choice of FLOAT).

Tested for x86_64 and x86 with GCC 6 in conjunction with the main
patch adding narrowing add functions.

	* math/libm-test-driver.c (snan_tests_arg): New variable.
	* math/libm-test-support.h (snan_tests_arg): New declaration.
	* math/libm-test-support.c (enable_test): Check snan_tests_arg.

1 files changed, 2 insertions, 1 deletions

diff --git a/math/libm-test-support.c b/math/libm-test-support.c
index e59f15b4d9..1a12ed6a39 100644
--- a/math/libm-test-support.c
+++ b/math/libm-test-support.c
@@ -985,7 +985,8 @@ enable_test (int exceptions)
     return 0;
   if (flag_test_finite && (exceptions & NON_FINITE) != 0)
     return 0;
-  if (!SNAN_TESTS (FLOAT) && (exceptions & TEST_SNAN) != 0)
+  if ((!SNAN_TESTS (FLOAT) || !snan_tests_arg)
+      && (exceptions & TEST_SNAN) != 0)
     return 0;
   if (flag_test_mathvec && (exceptions & NO_TEST_MATHVEC) != 0)
     return 0;