[PR66326, Cilk+] Fix FP exception occured in CilkPlus runtime

[Zamyatin, Igor]

Hi!

This patches fixes FP exception that comes from CilkPlus runtime.

Bootstrapped and regtested for x86_64.
Is it ok for trunk?

Thanks,
Igor

Changelog:

libcilkrts

2015-10-30  Igor Zamyatin  <igor.zamya...@intel.com>

        PR target/66326
        * untime/config/x86/os-unix-sysdep.c (sysdep_save_fp_ctrl_state):
        Use fnstcw instead fnstsw.


testsuite

2015-10-30  Igor Zamyatin  <igor.zamya...@intel.com>

        PR target/66326
        * g++.dg/cilk-plus/CK/pr66326.cc: New test.



diff --git a/gcc/testsuite/g++.dg/cilk-plus/CK/pr66326.cc 
b/gcc/testsuite/g++.dg/cilk-plus/CK/pr66326.cc
new file mode 100644
index 0000000..1114ebd
--- /dev/null
+++ b/gcc/testsuite/g++.dg/cilk-plus/CK/pr66326.cc
@@ -0,0 +1,33 @@
+/* { dg-options "-fcilkplus" } */
+/* { dg-do run { target i?86-*-* x86_64-*-* } } */
+/* { dg-options "-fcilkplus -lcilkrts" { target { i?86-*-* x86_64-*-* } } } */
+
+#include <cilk/cilk.h>
+#include <vector>
+#include <random>
+
+template <class T>
+void do_not_optimize_away(T&& x) {
+  asm volatile("" : "+r"(x));
+}
+
+const int N = 1'000'000;
+
+auto compute() {
+  std::vector<double> v(N);
+  auto rng = std::mt19937{std::random_device{}()};
+  std::uniform_real_distribution<double> dist(0, 1);
+  for (int i = 0; i < N; ++i) v[i] = std::log(std::sqrt(dist(rng)));
+  return v;
+}
+
+int main() {
+  std::vector<double> v1, v2, v3;
+  cilk_spawn [&] { v1 = compute(); }();
+  cilk_spawn [&] { v2 = compute(); }();
+  v3 = compute();
+  do_not_optimize_away(v1.data());
+  do_not_optimize_away(v2.data());
+  do_not_optimize_away(v3.data());
+  return 0;
+}
diff --git a/libcilkrts/runtime/config/x86/os-unix-sysdep.c 
b/libcilkrts/runtime/config/x86/os-unix-sysdep.c
index b505ddf..cbc7734 100644
--- a/libcilkrts/runtime/config/x86/os-unix-sysdep.c
+++ b/libcilkrts/runtime/config/x86/os-unix-sysdep.c
@@ -135,7 +135,7 @@ void sysdep_save_fp_ctrl_state(__cilkrts_stack_frame *sf)
         {
             __asm__ ("stmxcsr %0" : "=m" (sf->mxcsr));
         }
-        __asm__ ("fnstsw %0" : "=m" (sf->fpcsr));
+       __asm__ ("fnstcw %0" : "=m" (sf->fpcsr));
     }
 #endif
 }